Note: All code examples and UML diagrams in this article were generated by Claude 4.5 Sonnet
INTRODUCTION
The Capability-Centric Architecture represents a sophisticated architectural pattern that bridges the gap between embedded systems and enterprise applications. It provides a unified framework for managing complexity through well-defined Capabilities, each composed of an Essence layer containing pure domain logic, a Realization layer handling infrastructure integration, and an Adaptation layer managing external interactions. As software systems grow increasingly complex, architects and developers face mounting challenges in analyzing existing systems and designing new ones according to CCA principles. Large Language Models have emerged as powerful tools that can significantly enhance both the analysis and design phases of CCA-based systems.
Large Language Models are artificial intelligence systems trained on vast amounts of text data, enabling them to understand context, generate coherent text, and assist with complex reasoning tasks. When applied to software architecture, LLMs can help identify Capabilities from requirements, suggest appropriate Contract definitions, generate code structures, and even detect architectural antipatterns. This article explores how LLMs can be systematically applied to CCA analysis and design, and which UML diagram types software engineers should employ to effectively document and communicate CCA-based architectures.
HOW LLMS ASSIST IN CAPABILITY-CENTRIC ARCHITECTURE ANALYSIS
The analysis phase of CCA involves understanding an existing system or a set of requirements and decomposing them into appropriate Capabilities. This process requires deep domain knowledge, architectural expertise, and the ability to identify cohesive functional units. LLMs can significantly accelerate and improve this analysis through several mechanisms.
First, LLMs excel at extracting structured information from unstructured text. When provided with requirements documents, user stories, or existing system documentation, an LLM can identify potential Capabilities by recognizing patterns of cohesive functionality. For example, consider a requirements document for an industrial automation system. An architect might provide the following prompt to an LLM:
"Analyze the following requirements and identify potential Capabilities for a Capability-Centric Architecture. For each Capability, suggest what belongs in the Essence, Realization, and Adaptation layers. Requirements: The system must monitor temperature sensors across multiple zones, control heating elements to maintain target temperatures, log all sensor readings to a database, send alerts when temperatures exceed safety thresholds, and provide a web interface for operators to view current status and adjust setpoints."
The LLM might respond with a structured analysis identifying several Capabilities such as Temperature Monitoring Capability, Temperature Control Capability, Data Logging Capability, Alert Management Capability, and Operator Interface Capability. For each, it would suggest the appropriate layer decomposition. For instance, the Temperature Control Capability might have an Essence containing the PID control algorithm, a Realization handling direct hardware access to heating elements, and an Adaptation providing interfaces for setpoint adjustment and status queries.
Second, LLMs can assist in Contract definition by analyzing the interactions between identified Capabilities. Once Capabilities are identified, the LLM can suggest what each Capability should provide as Provisions, what it requires as Requirements, and what Protocols should govern the interactions. This is particularly valuable because defining clean Contracts is crucial for maintaining loose coupling and enabling independent evolution of Capabilities.
Consider this example where an architect asks an LLM to define a Contract. The prompt might be: "Define a Capability Contract for a Temperature Monitoring Capability that provides temperature readings to other Capabilities and requires calibration data. Include Provision, Requirement, and Protocol specifications."
The LLM might generate a detailed Contract specification similar to this structure:
/**
* Contract for Temperature Monitoring Capability.
* Defines interactions with other system Capabilities.
*/
public interface TemperatureMonitoringContract {
/**
* PROVISION: Services this Capability offers to others.
*/
interface Provision {
/**
* Subscribe to temperature updates at specified rate.
*
* @param subscriber Callback for temperature updates
* @param updateRateHz Desired update frequency in Hertz
*/
void subscribeToTemperatureUpdates(
TemperatureSubscriber subscriber,
double updateRateHz
);
/**
* Get current temperature reading.
*
* @param zoneId Identifier for temperature zone
* @return Current temperature in Celsius
*/
double getCurrentTemperature(String zoneId);
/**
* Retrieve historical temperature data.
*
* @param zoneId Zone identifier
* @param startTime Beginning of time range
* @param endTime End of time range
* @return Temperature history for specified period
*/
TemperatureHistory getHistory(
String zoneId,
Timestamp startTime,
Timestamp endTime
);
}
/**
* REQUIREMENT: Services this Capability needs from others.
*/
interface Requirement {
/**
* Obtain calibration parameters for a sensor.
*
* @param sensorId Unique sensor identifier
* @return Calibration data for converting raw readings
*/
CalibrationData getCalibration(String sensorId);
}
/**
* PROTOCOL: Interaction patterns and quality attributes.
*/
interface Protocol {
/**
* Maximum acceptable latency for temperature readings.
* Critical for real-time control loops.
*/
static final long MAX_LATENCY_MS = 10;
/**
* Minimum update rate that must be supported.
*/
static final double MIN_UPDATE_RATE_HZ = 0.1;
/**
* Maximum update rate that must be supported.
*/
static final double MAX_UPDATE_RATE_HZ = 1000.0;
/**
* Communication pattern for updates.
*/
enum CommunicationPattern {
SYNCHRONOUS_POLL,
ASYNCHRONOUS_PUSH,
HYBRID
}
}
}
This generated Contract demonstrates how an LLM can produce well-structured, documented code that follows CCA principles. The Contract clearly separates what the Capability provides through the Provision interface, what it requires through the Requirement interface, and the protocols governing interactions through the Protocol interface. Each method is properly documented with JavaDoc comments explaining its purpose, parameters, and return values. The indentation is consistent throughout, making the code easy to read and understand. Notice how the nested interfaces are indented four spaces from their parent interface, and method bodies or declarations are indented another four spaces, following standard Java conventions.
Third, LLMs can identify architectural antipatterns and suggest refactorings. When analyzing an existing system or a proposed design, an LLM can detect circular dependencies between Capabilities, overly broad Capabilities that violate the single responsibility principle, or Capabilities with poorly defined boundaries. For example, if an architect describes a design where Capability A depends on Capability B, which depends on Capability C, which in turn depends on Capability A, the LLM can identify this circular dependency and suggest introducing a new Capability that breaks the cycle.
Consider a scenario where an architect presents the following design to an LLM: "I have a Customer Management Capability that depends on Order Processing Capability to track customer purchase history. The Order Processing Capability depends on Inventory Management Capability to check product availability. The Inventory Management Capability depends on Customer Management Capability to analyze customer demand patterns for inventory forecasting."
The LLM would recognize the circular dependency pattern and might respond: "This design contains a circular dependency: Customer Management depends on Order Processing, which depends on Inventory Management, which depends back on Customer Management. This creates tight coupling and makes the system difficult to test and evolve. I recommend extracting a new Customer Analytics Capability that both Customer Management and Inventory Management can depend on. This new Capability would provide demand forecasting and purchase pattern analysis, breaking the cycle."
The LLM might then suggest the refactored structure:
Customer Management Capability
- Provides: Customer data, customer queries
- Requires: None
Order Processing Capability
- Provides: Order management, order history
- Requires: Customer data, Inventory availability
Inventory Management Capability
- Provides: Inventory availability, stock management
- Requires: Demand forecasts
Customer Analytics Capability (NEW)
- Provides: Demand forecasts, purchase pattern analysis
- Requires: Customer data, Order history
This refactoring eliminates the circular dependency by introducing a new Capability that consolidates the analytics concerns. Now the dependency graph is acyclic and follows a clear direction of information flow.
Fourth, LLMs can assist in Efficiency Gradient analysis by identifying critical paths in the system that require optimization. When provided with performance requirements and system descriptions, an LLM can suggest which operations should use direct hardware access with minimal abstraction and which can afford higher-level abstractions for improved maintainability. This is particularly valuable in systems that span the embedded-to-enterprise spectrum, where different parts of the system have vastly different performance requirements.
For instance, an architect might ask: "In a motor control system, which operations require the highest efficiency gradient and which can use higher abstractions?" The LLM might respond with an analysis like: "Critical real-time control loop operations such as reading encoder positions, calculating control outputs, and writing PWM values should use the highest efficiency gradient with direct hardware register access and minimal indirection. These operations must complete within microsecond timeframes. Medium-priority operations like sensor calibration, parameter validation, and state machine updates can use moderate abstractions with structured object-oriented code. Low-priority operations such as diagnostic logging, configuration management, and communication with monitoring systems can use the most flexible abstractions including database transactions, message queues, and network protocols."
HOW LLMS SUPPORT CAPABILITY-CENTRIC ARCHITECTURE DESIGN
Beyond analysis, LLMs provide substantial support during the design phase of CCA-based systems. The design phase involves making concrete decisions about Capability structure, implementation strategies, and system composition.
LLMs can generate skeleton implementations for Capabilities based on high-level descriptions. An architect can describe the desired functionality of a Capability, and the LLM can produce a complete skeleton including the Essence, Realization, and Adaptation layers with appropriate separation of concerns. For example, consider this prompt:
"Generate a skeleton implementation for a Payment Processing Capability in a Capability-Centric Architecture. The Essence should contain business rules for payment validation and fee calculation. The Realization should integrate with a payment gateway and database. The Adaptation should provide REST API endpoints and message queue consumers."
The LLM might generate a comprehensive implementation structure. First, the Essence layer:
/**
* Payment Processing Capability - Essence Layer
* Contains pure business logic for payment processing.
* No infrastructure dependencies, highly testable.
*/
public class PaymentProcessingEssence {
private final PaymentRules rules;
public PaymentProcessingEssence(PaymentRules rules) {
this.rules = rules;
}
/**
* Validates a payment request according to business rules.
* Pure function with no side effects or external dependencies.
*
* @param payment Payment request to validate
* @return Validation result with any errors
*/
public ValidationResult validatePayment(PaymentRequest payment) {
ValidationResult result = new ValidationResult();
// Validate amount is positive and within limits
if (payment.getAmount() <= 0) {
result.addError("Payment amount must be positive");
}
if (payment.getAmount() > rules.getMaxTransactionAmount()) {
result.addError("Payment amount exceeds maximum allowed");
}
// Validate currency is supported
if (!rules.isCurrencySupported(payment.getCurrency())) {
result.addError(
"Currency not supported: " + payment.getCurrency()
);
}
// Validate payment method
if (!rules.isPaymentMethodAllowed(payment.getMethod())) {
result.addError(
"Payment method not allowed: " + payment.getMethod()
);
}
return result;
}
/**
* Calculates processing fee for a payment.
* Pure calculation based on business rules.
*
* @param payment Payment request
* @return Calculated fee amount
*/
public double calculateFee(PaymentRequest payment) {
double baseRate = rules.getBaseFeeRate(payment.getMethod());
double amount = payment.getAmount();
// Calculate percentage-based fee
double fee = amount * baseRate;
// Apply minimum fee if applicable
double minFee = rules.getMinimumFee(payment.getMethod());
if (fee < minFee) {
fee = minFee;
}
// Apply maximum fee cap if applicable
double maxFee = rules.getMaximumFee(payment.getMethod());
if (fee > maxFee) {
fee = maxFee;
}
return fee;
}
/**
* Determines if a payment should be flagged for review.
* Applies business rules for fraud detection and risk assessment.
*
* @param payment Payment request
* @param customerHistory Customer's payment history
* @return True if payment should be reviewed
*/
public boolean requiresReview(
PaymentRequest payment,
CustomerHistory customerHistory
) {
// Flag high-value transactions
if (payment.getAmount() > rules.getReviewThreshold()) {
return true;
}
// Flag unusual patterns
if (customerHistory.isUnusualAmount(payment.getAmount())) {
return true;
}
// Flag new customers for first transaction
if (customerHistory.getTransactionCount() == 0) {
return true;
}
return false;
}
}
This Essence layer contains only pure business logic with no infrastructure dependencies. Each method is a pure function that takes inputs and produces outputs without side effects. The validatePayment method checks business rules for payment validity. The calculateFee method computes fees based on configurable rules. The requiresReview method applies risk assessment logic. All of these methods can be tested in isolation without any mocking of infrastructure components because they have no external dependencies beyond the injected PaymentRules configuration object.
Next, the LLM would generate the Realization layer:
/**
* Payment Processing Capability - Realization Layer
* Integrates with infrastructure services.
* Coordinates between Essence logic and external systems.
*/
public class PaymentProcessingRealization {
private final PaymentProcessingEssence essence;
private final PaymentGateway gateway;
private final PaymentDatabase database;
private final TransactionLog transactionLog;
public PaymentProcessingRealization(
PaymentProcessingEssence essence,
PaymentGateway gateway,
PaymentDatabase database,
TransactionLog transactionLog
) {
this.essence = essence;
this.gateway = gateway;
this.database = database;
this.transactionLog = transactionLog;
}
/**
* Processes a payment request end-to-end.
* Coordinates between Essence logic and infrastructure services.
*
* @param payment Payment request
* @return Processing result
*/
public PaymentResult processPayment(PaymentRequest payment) {
// Use Essence to validate payment
ValidationResult validation = essence.validatePayment(payment);
if (!validation.isValid()) {
return PaymentResult.rejected(validation.getErrors());
}
// Calculate fee using Essence
double fee = essence.calculateFee(payment);
// Retrieve customer history from database
CustomerHistory history = database.getCustomerHistory(
payment.getCustomerId()
);
// Check if review required using Essence
boolean needsReview = essence.requiresReview(payment, history);
if (needsReview) {
// Queue for manual review
database.queueForReview(payment);
return PaymentResult.pendingReview();
}
// Process through payment gateway
GatewayResponse response = gateway.processPayment(
payment.getAmount() + fee,
payment.getMethod(),
payment.getCustomerId()
);
// Store transaction in database
Transaction transaction = new Transaction(
payment,
fee,
response.getTransactionId(),
response.getStatus()
);
database.storeTransaction(transaction);
// Log transaction
transactionLog.log(transaction);
// Return result
if (response.isSuccessful()) {
return PaymentResult.success(
response.getTransactionId(),
fee
);
} else {
return PaymentResult.failed(response.getErrorMessage());
}
}
/**
* Retrieves payment status from database.
*
* @param transactionId Transaction identifier
* @return Current payment status
*/
public PaymentStatus getPaymentStatus(String transactionId) {
Transaction transaction = database.getTransaction(transactionId);
if (transaction == null) {
return PaymentStatus.notFound();
}
return PaymentStatus.fromTransaction(transaction);
}
/**
* Processes a refund for a previous payment.
*
* @param transactionId Original transaction to refund
* @param amount Amount to refund
* @return Refund result
*/
public RefundResult processRefund(String transactionId, double amount) {
// Retrieve original transaction
Transaction original = database.getTransaction(transactionId);
if (original == null) {
return RefundResult.transactionNotFound();
}
// Validate refund amount
if (amount > original.getAmount()) {
return RefundResult.invalidAmount(
"Refund amount exceeds original payment"
);
}
// Process refund through gateway
GatewayResponse response = gateway.processRefund(
transactionId,
amount
);
// Store refund transaction
Transaction refundTransaction = new Transaction(
original.getPaymentRequest(),
0.0,
response.getTransactionId(),
TransactionStatus.REFUNDED
);
database.storeTransaction(refundTransaction);
// Log refund
transactionLog.log(refundTransaction);
return RefundResult.success(response.getTransactionId());
}
}
The Realization layer orchestrates the interaction between the pure Essence logic and the infrastructure services. Notice how it delegates all business logic decisions to the Essence layer while handling all infrastructure concerns itself. The processPayment method follows a clear flow: validate using Essence, calculate fee using Essence, retrieve data from database, check review requirements using Essence, interact with payment gateway, store results in database, and log the transaction. This separation makes the code highly maintainable because business logic changes only affect the Essence while infrastructure changes only affect the Realization.
Finally, the LLM would generate the Adaptation layer:
/**
* Payment Processing Capability - Adaptation Layer
* Provides external interfaces for interaction.
* Handles REST API and message queue integration.
*/
public class PaymentProcessingAdaptation {
private final PaymentProcessingRealization realization;
private final MessageQueue messageQueue;
private final RESTServer restServer;
public PaymentProcessingAdaptation(
PaymentProcessingRealization realization,
MessageQueue messageQueue,
RESTServer restServer
) {
this.realization = realization;
this.messageQueue = messageQueue;
this.restServer = restServer;
}
/**
* Initialize adaptation layer.
* Sets up REST endpoints and message queue consumers.
*/
public void initialize() {
// Register REST endpoints
restServer.registerEndpoint(
"POST",
"/api/v1/payments",
this::handlePaymentRequest
);
restServer.registerEndpoint(
"GET",
"/api/v1/payments/{transactionId}",
this::handleStatusQuery
);
restServer.registerEndpoint(
"POST",
"/api/v1/payments/{transactionId}/refund",
this::handleRefundRequest
);
// Register message queue consumer
messageQueue.subscribe(
"payment.requests",
this::handlePaymentMessage
);
}
/**
* Handles REST API payment request.
*
* @param request HTTP request
* @return HTTP response
*/
private HTTPResponse handlePaymentRequest(HTTPRequest request) {
try {
// Parse payment request from JSON
PaymentRequest payment = parsePaymentRequest(
request.getBody()
);
// Process payment through Realization
PaymentResult result = realization.processPayment(payment);
// Convert result to HTTP response
if (result.isSuccessful()) {
return HTTPResponse.ok(serializeResult(result));
} else if (result.isPending()) {
return HTTPResponse.accepted(serializeResult(result));
} else {
return HTTPResponse.badRequest(serializeResult(result));
}
} catch (Exception e) {
return HTTPResponse.internalError(e.getMessage());
}
}
/**
* Handles REST API status query.
*
* @param request HTTP request
* @return HTTP response
*/
private HTTPResponse handleStatusQuery(HTTPRequest request) {
try {
String transactionId = request.getPathParameter(
"transactionId"
);
PaymentStatus status = realization.getPaymentStatus(
transactionId
);
if (status.isFound()) {
return HTTPResponse.ok(serializeStatus(status));
} else {
return HTTPResponse.notFound("Transaction not found");
}
} catch (Exception e) {
return HTTPResponse.internalError(e.getMessage());
}
}
/**
* Handles REST API refund request.
*
* @param request HTTP request
* @return HTTP response
*/
private HTTPResponse handleRefundRequest(HTTPRequest request) {
try {
String transactionId = request.getPathParameter(
"transactionId"
);
RefundRequest refund = parseRefundRequest(request.getBody());
RefundResult result = realization.processRefund(
transactionId,
refund.getAmount()
);
if (result.isSuccessful()) {
return HTTPResponse.ok(serializeRefundResult(result));
} else {
return HTTPResponse.badRequest(
serializeRefundResult(result)
);
}
} catch (Exception e) {
return HTTPResponse.internalError(e.getMessage());
}
}
/**
* Handles payment request from message queue.
*
* @param message Message from queue
*/
private void handlePaymentMessage(Message message) {
try {
PaymentRequest payment = deserializePaymentRequest(
message.getBody()
);
PaymentResult result = realization.processPayment(payment);
// Publish result to response queue
messageQueue.publish(
"payment.results",
serializeResult(result)
);
} catch (Exception e) {
// Handle error and potentially retry
messageQueue.publishError(
"payment.errors",
e.getMessage()
);
}
}
private PaymentRequest parsePaymentRequest(String json) {
// Parse JSON to PaymentRequest object
// Implementation would use Jackson or similar
return new PaymentRequest();
}
private PaymentRequest deserializePaymentRequest(byte[] data) {
// Deserialize from message format
// Implementation would use protocol buffers or similar
return new PaymentRequest();
}
private RefundRequest parseRefundRequest(String json) {
// Parse JSON to RefundRequest object
return new RefundRequest();
}
private String serializeResult(PaymentResult result) {
// Serialize result to JSON
// Implementation would use Jackson or similar
return "{}";
}
private String serializeStatus(PaymentStatus status) {
// Serialize status to JSON
return "{}";
}
private String serializeRefundResult(RefundResult result) {
// Serialize refund result to JSON
return "{}";
}
}
The Adaptation layer provides multiple interfaces for external interaction without mixing these concerns with the core business logic or infrastructure integration. It handles REST API endpoints for synchronous requests and message queue consumers for asynchronous processing. Notice how all the actual processing is delegated to the Realization layer. The Adaptation layer is purely concerned with protocol translation, converting HTTP requests to domain objects, invoking the Realization layer, and converting results back to HTTP responses or message queue messages.
This three-layer structure generated by the LLM demonstrates proper separation of concerns. The Essence contains testable business logic. The Realization coordinates infrastructure. The Adaptation handles external protocols. Each layer has a single, well-defined responsibility, and the dependencies flow in one direction from Adaptation to Realization to Essence.
LLMs can also assist in designing Evolution Envelopes for Capabilities. An Evolution Envelope defines how a Capability will evolve over time, including versioning strategies, deprecation policies, and migration paths. When asked to design an Evolution Envelope, an LLM can suggest appropriate semantic versioning schemes, identify which changes would constitute breaking changes versus backward-compatible additions, and propose migration strategies for consumers of the Capability.
For example, an architect might ask: "Design an Evolution Envelope for the Payment Processing Capability. We plan to add support for cryptocurrency payments in the next version and eventually deprecate check payments."
The LLM might generate:
/**
* Evolution Envelope for Payment Processing Capability.
* Defines versioning strategy and evolution plan.
*/
public class PaymentProcessingEvolutionEnvelope {
/**
* Current version of the Capability.
*/
public static final Version CURRENT_VERSION = new Version(2, 1, 0);
/**
* Supported versions for backward compatibility.
*/
public static final List<Version> SUPPORTED_VERSIONS = Arrays.asList(
new Version(2, 0, 0),
new Version(2, 1, 0)
);
/**
* Deprecated versions with sunset dates.
*/
public static final Map<Version, Date> DEPRECATED_VERSIONS = Map.of(
new Version(1, 0, 0), parseDate("2024-12-31"),
new Version(1, 5, 0), parseDate("2024-12-31")
);
/**
* Version history with change descriptions.
*/
public static final List<VersionChange> VERSION_HISTORY = Arrays.asList(
new VersionChange(
new Version(1, 0, 0),
"Initial release with credit card and debit card support"
),
new VersionChange(
new Version(1, 5, 0),
"Added check payment support"
),
new VersionChange(
new Version(2, 0, 0),
"Breaking change: Redesigned fee calculation API. " +
"Added multi-currency support. " +
"Deprecated check payments."
),
new VersionChange(
new Version(2, 1, 0),
"Added cryptocurrency payment support (Bitcoin, Ethereum). " +
"Enhanced fraud detection rules."
)
);
/**
* Planned future changes.
*/
public static final List<PlannedChange> ROADMAP = Arrays.asList(
new PlannedChange(
new Version(2, 2, 0),
"Q2 2024",
"Add support for additional cryptocurrencies (Litecoin, Ripple)"
),
new PlannedChange(
new Version(3, 0, 0),
"Q4 2024",
"Breaking change: Remove check payment support completely. " +
"Redesign refund API for better partial refund handling."
)
);
/**
* Deprecation policy for payment methods.
*/
public static class DeprecationPolicy {
/**
* Check payments are deprecated as of version 2.0.0.
* Will be removed in version 3.0.0.
* Clients should migrate to electronic payment methods.
*/
public static final PaymentMethodDeprecation CHECK_PAYMENT =
new PaymentMethodDeprecation(
PaymentMethod.CHECK,
new Version(2, 0, 0),
new Version(3, 0, 0),
"Migrate to credit card, debit card, or cryptocurrency"
);
}
/**
* Migration guide for version transitions.
*/
public static class MigrationGuide {
/**
* Migration from version 1.x to 2.0.
*/
public static String getV1ToV2MigrationGuide() {
return
"Migration Guide: Version 1.x to 2.0\n" +
"\n" +
"Breaking Changes:\n" +
"1. Fee calculation API changed\n" +
" Old: calculateFee(amount)\n" +
" New: calculateFee(PaymentRequest)\n" +
" Action: Update all fee calculation calls to pass " +
"full PaymentRequest object\n" +
"\n" +
"2. Currency handling\n" +
" Old: Assumed USD for all transactions\n" +
" New: Requires explicit currency in PaymentRequest\n" +
" Action: Add currency field to all payment requests\n" +
"\n" +
"3. Check payments deprecated\n" +
" Action: Plan migration away from check payments " +
"before version 3.0\n" +
"\n" +
"New Features:\n" +
"1. Multi-currency support\n" +
"2. Enhanced validation rules\n" +
"3. Improved error messages\n";
}
/**
* Migration from version 2.0 to 2.1.
*/
public static String getV2_0ToV2_1MigrationGuide() {
return
"Migration Guide: Version 2.0 to 2.1\n" +
"\n" +
"This is a backward-compatible update.\n" +
"No breaking changes.\n" +
"\n" +
"New Features:\n" +
"1. Cryptocurrency payment support\n" +
" - Bitcoin (BTC)\n" +
" - Ethereum (ETH)\n" +
" To use: Set paymentMethod to CRYPTOCURRENCY and " +
"specify cryptoCurrency field\n" +
"\n" +
"2. Enhanced fraud detection\n" +
" - Improved pattern recognition\n" +
" - Lower false positive rate\n" +
" No action required, automatically applied\n";
}
}
private static Date parseDate(String dateString) {
// Parse date string to Date object
return new Date();
}
}
This Evolution Envelope provides a complete picture of how the Capability evolves over time. It defines the current version, lists supported versions for backward compatibility, identifies deprecated versions with sunset dates, maintains a version history, outlines a roadmap for future changes, specifies deprecation policies for specific features, and provides detailed migration guides for version transitions. This level of planning enables consumers of the Capability to understand what changes are coming and how to prepare for them.
Furthermore, LLMs can help design the Capability Registry and dependency management mechanisms. The Capability Registry is a critical component that tracks all Capabilities, their Contracts, and their bindings while preventing circular dependencies. An LLM can generate code for a registry that performs topological sorting to determine initialization order, validates Contract compatibility, and detects dependency cycles.
Here is an example of a Capability Registry that an LLM might generate:
/**
* Registry that manages Capabilities and their interactions.
* Central coordination point for the architecture.
* Prevents circular dependencies and manages initialization order.
*/
public class CapabilityRegistry {
private final Map<String, CapabilityDescriptor> capabilities;
private final Map<String, List<ContractBinding>> bindings;
private final DependencyGraph dependencyGraph;
public CapabilityRegistry() {
this.capabilities = new ConcurrentHashMap<>();
this.bindings = new ConcurrentHashMap<>();
this.dependencyGraph = new DependencyGraph();
}
/**
* Registers a Capability in the system.
*
* @param descriptor Description of the Capability including Contract
* @throws IllegalArgumentException if descriptor is invalid
* @throws ContractConflictException if Contract conflicts with existing
*/
public void registerCapability(CapabilityDescriptor descriptor) {
// Validate descriptor
validateDescriptor(descriptor);
// Check Contract compatibility with existing Capabilities
checkContractCompatibility(descriptor);
// Register Capability
capabilities.put(descriptor.getName(), descriptor);
// Add to dependency graph
dependencyGraph.addNode(descriptor.getName());
// Resolve pending bindings
resolvePendingBindings(descriptor);
}
/**
* Binds a requirement of one Capability to provision of another.
*
* @param consumer The Capability that requires something
* @param provider The Capability that provides it
* @param contractType The type of Contract being bound
* @throws IllegalArgumentException if Capabilities not registered
* @throws CircularDependencyException if binding creates cycle
*/
public void bindCapabilities(
String consumer,
String provider,
Class<?> contractType
) {
CapabilityDescriptor consumerDesc = capabilities.get(consumer);
CapabilityDescriptor providerDesc = capabilities.get(provider);
if (consumerDesc == null || providerDesc == null) {
throw new IllegalArgumentException(
"Both Capabilities must be registered"
);
}
// Verify provider actually provides this Contract
if (!providerDesc.provides(contractType)) {
throw new IllegalArgumentException(
provider + " does not provide " + contractType.getName()
);
}
// Verify consumer actually requires this Contract
if (!consumerDesc.requires(contractType)) {
throw new IllegalArgumentException(
consumer + " does not require " + contractType.getName()
);
}
// Check if binding would create circular dependency
if (dependencyGraph.wouldCreateCycle(consumer, provider)) {
throw new CircularDependencyException(
"Binding " + consumer + " -> " + provider +
" would create circular dependency"
);
}
// Create binding
ContractBinding binding = new ContractBinding(
consumer,
provider,
contractType
);
// Store binding
bindings.computeIfAbsent(consumer, k -> new ArrayList<>())
.add(binding);
// Update dependency graph
dependencyGraph.addEdge(consumer, provider);
}
/**
* Gets initialization order for all Capabilities.
* Uses topological sort to ensure dependencies initialized first.
*
* @return List of Capability names in initialization order
* @throws CircularDependencyException if cycles detected
*/
public List<String> getInitializationOrder() {
return dependencyGraph.topologicalSort();
}
/**
* Gets all bindings for a Capability.
*
* @param capabilityName Name of the Capability
* @return List of Contract bindings
*/
public List<ContractBinding> getBindings(String capabilityName) {
return bindings.getOrDefault(capabilityName, Collections.emptyList());
}
/**
* Gets descriptor for a Capability.
*
* @param capabilityName Name of the Capability
* @return Capability descriptor or null if not found
*/
public CapabilityDescriptor getCapability(String capabilityName) {
return capabilities.get(capabilityName);
}
/**
* Validates a Capability descriptor.
*
* @param descriptor Descriptor to validate
* @throws IllegalArgumentException if invalid
*/
private void validateDescriptor(CapabilityDescriptor descriptor) {
if (descriptor.getName() == null ||
descriptor.getName().isEmpty()) {
throw new IllegalArgumentException(
"Capability must have a name"
);
}
if (descriptor.getContract() == null) {
throw new IllegalArgumentException(
"Capability must have a Contract"
);
}
if (descriptor.getEvolutionEnvelope() == null) {
throw new IllegalArgumentException(
"Capability must have an Evolution Envelope"
);
}
}
/**
* Checks if new Capability Contract conflicts with existing ones.
*
* @param descriptor New Capability descriptor
* @throws ContractConflictException if conflict detected
*/
private void checkContractCompatibility(
CapabilityDescriptor descriptor
) {
// Check if existing Capability provides same Contract
for (CapabilityDescriptor existing : capabilities.values()) {
if (existing.provides(descriptor.getContract().getClass())) {
// Multiple providers for same Contract
// Ensure they are compatible
if (!areContractsCompatible(
existing.getContract(),
descriptor.getContract()
)) {
throw new ContractConflictException(
"Incompatible Contracts: " + existing.getName() +
" and " + descriptor.getName()
);
}
}
}
}
/**
* Checks if two Contracts are compatible.
*
* @param contract1 First Contract
* @param contract2 Second Contract
* @return True if compatible
*/
private boolean areContractsCompatible(
Object contract1,
Object contract2
) {
// Contracts compatible if same interface and compatible versions
return contract1.getClass().equals(contract2.getClass());
}
/**
* Resolves bindings that were waiting for this Capability.
*
* @param descriptor Newly registered Capability
*/
private void resolvePendingBindings(CapabilityDescriptor descriptor) {
// Check if any Capabilities were waiting for this one
for (CapabilityDescriptor waiting : capabilities.values()) {
for (Class<?> required : waiting.getRequiredContracts()) {
if (descriptor.provides(required)) {
bindCapabilities(
waiting.getName(),
descriptor.getName(),
required
);
}
}
}
}
}
This Capability Registry implementation demonstrates several important features. It maintains a map of all registered Capabilities and their bindings. It uses a dependency graph to track relationships between Capabilities. When binding Capabilities, it checks whether the binding would create a circular dependency before allowing it. It can compute a topological sort of the dependency graph to determine the correct initialization order. It validates that Capability descriptors are complete and that Contracts are compatible. It automatically resolves pending bindings when a new Capability is registered that provides a Contract that other Capabilities were waiting for.
The dependency graph implementation that supports the registry might look like this:
/**
* Directed graph for tracking Capability dependencies.
* Supports cycle detection and topological sorting.
*/
public class DependencyGraph {
private final Map<String, Set<String>> adjacencyList;
private final Map<String, Integer> inDegree;
public DependencyGraph() {
this.adjacencyList = new HashMap<>();
this.inDegree = new HashMap<>();
}
/**
* Adds a node to the graph.
*
* @param node Node identifier
*/
public void addNode(String node) {
adjacencyList.putIfAbsent(node, new HashSet<>());
inDegree.putIfAbsent(node, 0);
}
/**
* Adds a directed edge from source to target.
* Represents source depending on target.
*
* @param source Source node (consumer)
* @param target Target node (provider)
*/
public void addEdge(String source, String target) {
adjacencyList.get(source).add(target);
inDegree.put(target, inDegree.get(target) + 1);
}
/**
* Checks if adding an edge would create a cycle.
*
* @param source Source node
* @param target Target node
* @return True if edge would create cycle
*/
public boolean wouldCreateCycle(String source, String target) {
// Temporarily add edge
Set<String> originalEdges = new HashSet<>(
adjacencyList.get(source)
);
adjacencyList.get(source).add(target);
// Check for cycle using DFS
boolean hasCycle = hasCycle();
// Restore original state
adjacencyList.put(source, originalEdges);
return hasCycle;
}
/**
* Performs topological sort to get initialization order.
*
* @return List of nodes in topological order
* @throws CircularDependencyException if cycle exists
*/
public List<String> topologicalSort() {
// Create copy of in-degree map
Map<String, Integer> inDegreeCopy = new HashMap<>(inDegree);
// Queue for nodes with no dependencies
Queue<String> queue = new LinkedList<>();
for (Map.Entry<String, Integer> entry : inDegreeCopy.entrySet()) {
if (entry.getValue() == 0) {
queue.offer(entry.getKey());
}
}
// Result list
List<String> result = new ArrayList<>();
// Process nodes
while (!queue.isEmpty()) {
String node = queue.poll();
result.add(node);
// Reduce in-degree for neighbors
for (String neighbor : adjacencyList.get(node)) {
int newInDegree = inDegreeCopy.get(neighbor) - 1;
inDegreeCopy.put(neighbor, newInDegree);
if (newInDegree == 0) {
queue.offer(neighbor);
}
}
}
// Check if all nodes processed
if (result.size() != adjacencyList.size()) {
throw new CircularDependencyException(
"Circular dependency detected in Capability graph"
);
}
return result;
}
/**
* Checks if graph contains a cycle using DFS.
*
* @return True if cycle exists
*/
private boolean hasCycle() {
Set<String> visited = new HashSet<>();
Set<String> recursionStack = new HashSet<>();
for (String node : adjacencyList.keySet()) {
if (hasCycleUtil(node, visited, recursionStack)) {
return true;
}
}
return false;
}
/**
* Utility method for cycle detection using DFS.
*
* @param node Current node
* @param visited Set of visited nodes
* @param recursionStack Set of nodes in current recursion stack
* @return True if cycle detected
*/
private boolean hasCycleUtil(
String node,
Set<String> visited,
Set<String> recursionStack
) {
if (recursionStack.contains(node)) {
return true;
}
if (visited.contains(node)) {
return false;
}
visited.add(node);
recursionStack.add(node);
for (String neighbor : adjacencyList.get(node)) {
if (hasCycleUtil(neighbor, visited, recursionStack)) {
return true;
}
}
recursionStack.remove(node);
return false;
}
}
This dependency graph implementation provides the core algorithms needed for dependency management. It maintains an adjacency list representation of the directed graph where an edge from A to B means A depends on B. It tracks the in-degree of each node to support topological sorting. The wouldCreateCycle method allows checking whether a proposed edge would create a cycle before actually adding it. The topologicalSort method uses Kahn's algorithm to produce an ordering where dependencies come before dependents. The hasCycle method uses depth-first search with a recursion stack to detect cycles.
UML DIAGRAM TYPES FOR CAPABILITY-CENTRIC ARCHITECTURE
Unified Modeling Language provides a standardized way to visualize software architecture. For CCA-based systems, certain UML diagram types are particularly valuable for documenting and communicating the architecture. Software engineers working with CCA should employ the following diagram types.
Component Diagrams are essential for showing the high-level structure of a CCA system. In a Component Diagram, each Capability is represented as a component, and the dependencies between Capabilities are shown through provided and required interfaces that correspond to Capability Contracts. A Component Diagram for a simple temperature control system might look like this in ASCII representation:
+-------------------------+ +-------------------------+
| Temperature Monitoring | | Alert Management |
| Capability | | Capability |
| | | |
| <<provides>> | | <<provides>> |
| ITempMonitor ----+---------->+ <<requires>> |
| | | ITempMonitor |
+-------------------------+ +-------------------------+
|
| <<requires>>
| ICalibration
|
v
+-------------------------+
| Calibration Management |
| Capability |
| |
| <<provides>> |
| ICalibration |
+-------------------------+
This diagram shows three Capabilities with their provided and required interfaces. The Temperature Monitoring Capability provides the ITempMonitor interface and requires the ICalibration interface. The Alert Management Capability requires the ITempMonitor interface. The Calibration Management Capability provides the ICalibration interface. This clearly shows the dependency structure and helps identify potential circular dependencies. The arrows indicate the direction of dependency, with the arrow pointing from the consumer to the provider. This visualization makes it immediately obvious that there are no circular dependencies in this design because all arrows flow in one direction through the dependency graph.
For a more complex system with multiple Capabilities, the Component Diagram becomes even more valuable. Consider a payment processing system:
+--------------------+ +--------------------+ +--------------------+
| User Authentication| | Payment Processing | | Fraud Detection |
| Capability | | Capability | | Capability |
| | | | | |
| <<provides>> | | <<provides>> | | <<provides>> |
| IAuthentication----+---->+ <<requires>> | | IFraudCheck +
| | | IAuthentication | | |
+--------------------+ | | +--------------------+
| <<requires>> | ^
| IFraudCheck ----+ |
| | |
| <<requires>> | |
| IPaymentGateway----+ |
+--------------------+ |
| |
v |
+--------------------+ |
| Payment Gateway | |
| Capability | |
| | |
| <<provides>> | |
| IPaymentGateway | |
| | |
| <<requires>> +--------------+
| IFraudCheck |
+--------------------+
This more complex diagram shows how multiple Capabilities interact. The Payment Processing Capability depends on three other Capabilities: User Authentication for verifying user identity, Fraud Detection for risk assessment, and Payment Gateway for actual payment processing. The Payment Gateway Capability also depends on Fraud Detection, creating a shared dependency. This diagram helps architects understand the overall system structure and identify which Capabilities are central to the architecture and which are more peripheral.
Class Diagrams are valuable for showing the internal structure of a Capability, particularly the relationships between the Essence, Realization, and Adaptation layers. A Class Diagram for a single Capability might show:
+-------------------------------+
| PaymentProcessingEssence |
+-------------------------------+
| - rules: PaymentRules |
+-------------------------------+
| + validatePayment() |
| + calculateFee() |
| + requiresReview() |
+-------------------------------+
^
| uses
|
+-------------------------------+
| PaymentProcessingRealization |
+-------------------------------+
| - essence: Essence |
| - gateway: Gateway |
| - database: Database |
| - transactionLog: Log |
+-------------------------------+
| + processPayment() |
| + getPaymentStatus() |
| + processRefund() |
+-------------------------------+
^
| uses
|
+-------------------------------+
| PaymentProcessingAdaptation |
+-------------------------------+
| - realization: Realization |
| - messageQueue: Queue |
| - restServer: Server |
+-------------------------------+
| + initialize() |
| - handlePaymentRequest() |
| - handleStatusQuery() |
| - handleRefundRequest() |
| - handlePaymentMessage() |
+-------------------------------+
This diagram shows the layered structure within a Capability, with the Adaptation layer depending on the Realization layer, which in turn depends on the Essence layer. This visualization helps ensure proper separation of concerns and dependency direction. The arrows point upward from dependent to dependency, showing that the Adaptation layer uses the Realization layer, and the Realization layer uses the Essence layer. This is the correct dependency direction in CCA, ensuring that the pure domain logic in the Essence has no dependencies on infrastructure concerns.
A more detailed Class Diagram might also show the relationships between classes within a layer. For example, the Essence layer might contain multiple classes:
+-------------------------------+
| PaymentProcessingEssence |
+-------------------------------+
| - rules: PaymentRules |
| - validator: PaymentValidator |
| - feeCalculator: FeeCalculator|
+-------------------------------+
| + validatePayment() |
| + calculateFee() |
| + requiresReview() |
+-------------------------------+
|
| uses
v
+-------------------------------+ +-------------------------------+
| PaymentValidator | | FeeCalculator |
+-------------------------------+ +-------------------------------+
| - rules: PaymentRules | | - rules: PaymentRules |
+-------------------------------+ +-------------------------------+
| + validateAmount() | | + calculateBaseFee() |
| + validateCurrency() | | + applyMinimumFee() |
| + validateMethod() | | + applyMaximumCap() |
+-------------------------------+ +-------------------------------+
This shows how the Essence layer might be decomposed into multiple collaborating classes, each with a specific responsibility. The PaymentProcessingEssence orchestrates the PaymentValidator and FeeCalculator, both of which use the PaymentRules configuration object.
Sequence Diagrams are crucial for showing the dynamic behavior of interactions between Capabilities. They illustrate the order of operations when a request flows through multiple Capabilities. For example, a Sequence Diagram for processing a payment might show:
User PaymentAdapt PaymentReal PaymentEssence Gateway Database
| | | | | |
|---------->| | | | |
| POST | | | | |
| /payments | | | | |
| |-------------->| | | |
| | processPayment| | | |
| | |-------------->| | |
| | | validatePayment | |
| | |<--------------| | |
| | | ValidationResult | |
| | |-------------->| | |
| | | calculateFee | | |
| | |<--------------| | |
| | | fee | | |
| | |----------------------------->| |
| | | getCustomerHistory | |
| | |<-----------------------------| |
| | | CustomerHistory | |
| | |-------------->| | |
| | | requiresReview| | |
| | |<--------------| | |
| | | false | | |
| | |------------------------------> |
| | | processPayment | |
| | |<------------------------------ |
| | | GatewayResponse | |
| | |-------------------------------------> |
| | | storeTransaction | |
| | |<-----------------------------------————-| |
| | | success | | |
| |<--------------| | | |
| | PaymentResult | | | |
|<----------| | | | |
| HTTP 200 | | | | |
| OK | | | | |
This Sequence Diagram shows the flow of a payment processing request through the system. The User sends an HTTP POST request to the PaymentAdaptation layer. The Adaptation layer delegates to the PaymentRealization layer. The Realization layer first calls the PaymentEssence to validate the payment and calculate the fee. It then retrieves customer history from the Database and asks the Essence whether the payment requires review. Since review is not required in this scenario, the Realization proceeds to process the payment through the Gateway, stores the transaction in the Database, and returns the result through the Adaptation layer back to the User. This diagram makes the sequence of operations explicit and shows how the different layers and components collaborate to fulfill the request.
Sequence Diagrams are particularly valuable for understanding complex interactions involving multiple Capabilities. Consider a more complex scenario where a payment requires fraud detection:
User PaymentAdapt PaymentReal PaymentEss AuthCap FraudCap Gateway Database
| | | | | | | |
|--------->| | | | | | |
| POST | | | | | | |
| |----------->| | | | | |
| | |-------------------------> | | |
| | | authenticateUser | | | |
| | |<----------------------| | | |
| | | AuthToken | | | |
| | |-----------> | | | |
| | | validate | | | | |
| | |<-----------| | | | |
| | | valid | | | | |
| | |-----------> | | | |
| | | calculateFee | | | |
| | |<-----------| | | | |
| | | fee | | | | |
| | |----------------------------------> | |
| | | checkFraudRisk | | | |
| | |<------------------------------------ | |
| | | RiskScore | | | |
| | |-----------> | | | |
| | | requiresReview | | | |
| | |<-----------| | | | |
| | | false | | | | |
| | |----------------------------------------------> |
| | | processPayment | | | |
| | |<---------------------------------------------- |
| | | GatewayResponse | | | |
| | |--------------------------------------------------> |
| | | storeTransaction | | |
| | |<-------------------------------------------| |
| |<-----------| | | | | |
|<---------| | | | | | |
| HTTP 200 | | | | | | |
This more complex Sequence Diagram shows interactions with multiple Capabilities. The Payment Processing Capability interacts with the Authentication Capability to verify the user, the Fraud Detection Capability to assess risk, the Payment Gateway Capability to process the payment, and the Database to store the transaction. This visualization helps developers understand the complete flow of control and data through the system.
Use Case Diagrams are valuable for identifying Capabilities during the analysis phase. They show the functional requirements of the system from the perspective of external actors. Each use case often corresponds to one or more Capabilities working together. A Use Case Diagram for a temperature control system might look like:
Temperature Control System
+-------------+
| Operator |
+-------------+
|
|
+----------------+----------------+----------------+
| | | |
v v v v
+--------------+ +-------------+ +-------------+ +-------------+
| View Current | | Adjust | | View | | Configure |
| Temperature | | Setpoint | | History | | Alerts |
+--------------+ +-------------+ +-------------+ +-------------+
+-------------+
| System |
+-------------+
|
|
+----------------+
| |
v v
+--------------+ +-------------+
| Monitor | | Send |
| Temperature | | Alerts |
+--------------+ +-------------+
This Use Case Diagram shows two actors: the Operator who interacts with the system manually, and the System itself which performs automated functions. The Operator can view current temperature, adjust setpoints, view historical data, and configure alerts. The System automatically monitors temperature and sends alerts when thresholds are exceeded. From this Use Case Diagram, an architect can identify potential Capabilities such as Temperature Monitoring Capability for the monitor temperature use case, Temperature Control Capability for the adjust setpoint use case, Data Logging Capability for the view history use case, and Alert Management Capability for the configure alerts and send alerts use cases.
Deployment Diagrams show the physical deployment of artifacts on nodes. In CCA, this is particularly useful for distinguishing between embedded and enterprise components and visualizing how Capabilities are distributed across different hardware environments. A Deployment Diagram for a distributed temperature control system might look like:
+----------------------------------+ +----------------------------------+
| <<Node>> Embedded Controller | | <<Node>> Cloud Server |
| (ARM Cortex-M4, 256KB RAM) | | (Linux, 16GB RAM) |
| | | |
| +--------------+ | | +--------------+ |
| | Temperature | | | | Data Logging | |
| | Monitoring | | | | Capability | |
| | Capability | | | +--------------+ |
| +--------------+ | | |
| | | +--------------+ |
| +--------------+ | | | Alert | |
| | Temperature | | MQTT | | Management | |
| | Control |<----------------+--------->| | Capability | |
| | Capability | | over TCP | +--------------+ |
| +--------------+ | | |
| | | +--------------+ |
| +--------------+ | | | Web | |
| | Calibration | | | | Interface | |
| | Management | | | | Capability | |
| | Capability | | | +--------------+ |
| +--------------+ | | |
+----------------------------------+ +----------------------------------+
This Deployment Diagram shows how Capabilities are distributed between an embedded controller and a cloud server. The embedded controller runs the Temperature Monitoring, Temperature Control, and Calibration Management Capabilities, which require direct hardware access and real-time performance. The cloud server runs the Data Logging, Alert Management, and Web Interface Capabilities, which benefit from the scalability and storage capacity of cloud infrastructure. The two nodes communicate over MQTT, a lightweight messaging protocol suitable for constrained devices. This visualization helps architects make decisions about where to deploy each Capability based on its requirements and constraints.
Activity Diagrams can be used to show the workflow within a Capability or across multiple Capabilities. They are particularly useful for documenting complex business processes that involve decision points and parallel activities. An Activity Diagram for payment processing might look like:
[Start Payment Processing]
|
v
+----------------------+
| Validate Payment |
+----------------------+
|
+---------------+---------------+
| |
[Invalid] [Valid]
| |
v v
+--------------+ +------------------+
| Return Error | | Calculate Fee |
+--------------+ +------------------+
| |
| v
| +------------------+
| | Get Customer |
| | History |
| +------------------+
| |
| v
| +------------------+
| | Check Fraud Risk |
| +------------------+
| |
| +---------------+---------------+
| | |
| [High Risk] [Low Risk]
| | |
| v v
| +----------------+ +------------------+
| | Queue for | | Process via |
| | Manual Review | | Gateway |
| +----------------+ +------------------+
| | |
| v v
| +----------------+ +------------------+
| | Return Pending | | Store Transaction|
| +----------------+ +------------------+
| | |
| | v
| | +------------------+
| | | Return Success |
| | +------------------+
| | |
+---------------+---------------+---------------+
|
v
[End Payment Processing]
This Activity Diagram shows the workflow for processing a payment, including decision points for validation and fraud risk assessment. It clearly shows the different paths a payment can take through the system: immediate rejection for invalid payments, queuing for manual review for high-risk payments, and automatic processing for low-risk valid payments. This type of diagram helps developers understand the complete business logic and ensures that all edge cases are handled.
State Machine Diagrams are useful for showing the lifecycle of entities within a Capability. For example, a payment transaction might go through various states:
+-------------+
| Created |
+-------------+
|
| submit
v
+-------------+
| Validating |
+-------------+
| |
validation failed validation succeeded
| |
v v
+----------+ +-------------+
| Rejected | | Pending |
+----------+ +-------------+
| |
fraud check | | low risk
high risk | |
v v
+----------+ +-------------+
| Under | | Processing |
| Review | +-------------+
+----------+ |
| | gateway response
| |
approved| +---+---+
| | |
v v v
+----------+ +----------+
| Processing| | Failed |
+----------+ +----------+
|
gateway success
|
v
+----------+
| Completed|
+----------+
|
refund requested
|
v
+----------+
| Refunded |
+----------+
This State Machine Diagram shows all possible states a payment transaction can be in and the transitions between states. A transaction starts in the Created state, moves to Validating when submitted, and then either becomes Rejected if validation fails or Pending if validation succeeds. From Pending, it either goes to Under Review for high-risk payments or directly to Processing for low-risk payments. Processing can result in either Completed or Failed depending on the gateway response. A Completed payment can later be Refunded. This diagram helps developers implement the state management logic correctly and ensures that all state transitions are properly handled.
PRACTICAL IMPLEMENTATION GUIDANCE
When using LLMs to assist with CCA analysis and design, software engineers should follow certain best practices to maximize the value of LLM assistance while maintaining architectural quality.
First, provide clear and detailed prompts. The quality of LLM output depends heavily on the quality of the input prompt. When asking an LLM to identify Capabilities, provide comprehensive requirements including functional requirements, non-functional requirements, quality attributes, and constraints. When asking for code generation, specify the programming language, coding standards, documentation requirements, and any specific patterns or libraries that should be used.
Second, iterate and refine. LLM-generated designs and code should be treated as starting points, not final solutions. Review the LLM output critically, identify areas that need improvement, and provide feedback to the LLM to generate refined versions. For example, if an LLM generates a Capability Contract that is too broad, ask it to split the Contract into multiple more focused Contracts.
Third, validate architectural principles. Ensure that LLM-generated designs adhere to CCA principles such as proper layer separation, unidirectional dependencies, and Contract-based interaction. If an LLM suggests a design where the Essence layer depends on infrastructure components, reject that suggestion and ask for a corrected design.
Fourth, combine LLM assistance with human expertise. LLMs are tools that augment human capabilities, not replacements for human architects. Use LLMs to handle routine tasks like generating boilerplate code, drafting documentation, and identifying common patterns, but rely on human judgment for critical architectural decisions, domain-specific optimizations, and trade-off analysis.
Fifth, maintain consistency across the codebase. When using LLMs to generate code for multiple Capabilities, ensure that the generated code follows consistent patterns, naming conventions, and structural organization. This might require creating templates or style guides that you provide to the LLM as part of your prompts.
Sixth, test thoroughly. LLM-generated code should be tested as rigorously as human-written code. The separation of concerns in CCA actually makes testing easier because the Essence layer can be unit tested without any infrastructure dependencies, the Realization layer can be integration tested with mocked infrastructure, and the Adaptation layer can be tested with Contract tests.
Here is an example of a comprehensive test suite for the Payment Processing Capability that an LLM might generate:
/**
* Test suite for Payment Processing Capability - Essence Layer.
* These are pure unit tests with no infrastructure dependencies.
*/
public class PaymentProcessingEssenceTest {
private PaymentRules rules;
private PaymentProcessingEssence essence;
@Before
public void setUp() {
// Create test configuration
rules = new PaymentRules();
rules.setMaxTransactionAmount(10000.00);
rules.setReviewThreshold(5000.00);
rules.addSupportedCurrency("USD");
rules.addSupportedCurrency("EUR");
rules.addAllowedPaymentMethod(PaymentMethod.CREDIT_CARD);
rules.addAllowedPaymentMethod(PaymentMethod.DEBIT_CARD);
rules.setBaseFeeRate(PaymentMethod.CREDIT_CARD, 0.029);
rules.setMinimumFee(PaymentMethod.CREDIT_CARD, 0.30);
// Create Essence instance
essence = new PaymentProcessingEssence(rules);
}
@Test
public void testValidatePayment_ValidPayment_ReturnsValid() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(100.00);
payment.setCurrency("USD");
payment.setMethod(PaymentMethod.CREDIT_CARD);
// Act
ValidationResult result = essence.validatePayment(payment);
// Assert
assertTrue(result.isValid());
assertEquals(0, result.getErrors().size());
}
@Test
public void testValidatePayment_NegativeAmount_ReturnsInvalid() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(-50.00);
payment.setCurrency("USD");
payment.setMethod(PaymentMethod.CREDIT_CARD);
// Act
ValidationResult result = essence.validatePayment(payment);
// Assert
assertFalse(result.isValid());
assertTrue(result.getErrors().contains(
"Payment amount must be positive"
));
}
@Test
public void testValidatePayment_AmountExceedsMaximum_ReturnsInvalid() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(15000.00);
payment.setCurrency("USD");
payment.setMethod(PaymentMethod.CREDIT_CARD);
// Act
ValidationResult result = essence.validatePayment(payment);
// Assert
assertFalse(result.isValid());
assertTrue(result.getErrors().contains(
"Payment amount exceeds maximum allowed"
));
}
@Test
public void testValidatePayment_UnsupportedCurrency_ReturnsInvalid() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(100.00);
payment.setCurrency("GBP");
payment.setMethod(PaymentMethod.CREDIT_CARD);
// Act
ValidationResult result = essence.validatePayment(payment);
// Assert
assertFalse(result.isValid());
assertTrue(result.getErrors().contains(
"Currency not supported: GBP"
));
}
@Test
public void testCalculateFee_StandardAmount_ReturnsCorrectFee() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(100.00);
payment.setMethod(PaymentMethod.CREDIT_CARD);
// Act
double fee = essence.calculateFee(payment);
// Assert
// 100.00 * 0.029 = 2.90
assertEquals(2.90, fee, 0.01);
}
@Test
public void testCalculateFee_SmallAmount_AppliesMinimumFee() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(5.00);
payment.setMethod(PaymentMethod.CREDIT_CARD);
// Act
double fee = essence.calculateFee(payment);
// Assert
// 5.00 * 0.029 = 0.145, but minimum is 0.30
assertEquals(0.30, fee, 0.01);
}
@Test
public void testRequiresReview_HighValueTransaction_ReturnsTrue() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(7000.00);
payment.setMethod(PaymentMethod.CREDIT_CARD);
CustomerHistory history = new CustomerHistory();
history.setTransactionCount(10);
history.setAverageAmount(500.00);
// Act
boolean requiresReview = essence.requiresReview(payment, history);
// Assert
assertTrue(requiresReview);
}
@Test
public void testRequiresReview_NewCustomer_ReturnsTrue() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(100.00);
payment.setMethod(PaymentMethod.CREDIT_CARD);
CustomerHistory history = new CustomerHistory();
history.setTransactionCount(0);
// Act
boolean requiresReview = essence.requiresReview(payment, history);
// Assert
assertTrue(requiresReview);
}
@Test
public void testRequiresReview_NormalTransaction_ReturnsFalse() {
// Arrange
PaymentRequest payment = new PaymentRequest();
payment.setAmount(100.00);
payment.setMethod(PaymentMethod.CREDIT_CARD);
CustomerHistory history = new CustomerHistory();
history.setTransactionCount(50);
history.setAverageAmount(120.00);
history.setStandardDeviation(30.00);
// Act
boolean requiresReview = essence.requiresReview(payment, history);
// Assert
assertFalse(requiresReview);
}
}
This test suite demonstrates proper testing of the Essence layer. All tests are pure unit tests with no infrastructure dependencies. They test the business logic in isolation, covering normal cases, edge cases, and error conditions. The tests are fast, deterministic, and provide comprehensive coverage of the Essence layer's functionality.
For the Realization layer, integration tests would be appropriate:
/**
* Test suite for Payment Processing Capability - Realization Layer.
* These are integration tests with mocked infrastructure.
*/
public class PaymentProcessingRealizationTest {
private PaymentProcessingEssence essence;
private PaymentGateway mockGateway;
private PaymentDatabase mockDatabase;
private TransactionLog mockLog;
private PaymentProcessingRealization realization;
@Before
public void setUp() {
// Create Essence with test configuration
PaymentRules rules = createTestRules();
essence = new PaymentProcessingEssence(rules);
// Create mocks for infrastructure
mockGateway = mock(PaymentGateway.class);
mockDatabase = mock(PaymentDatabase.class);
mockLog = mock(TransactionLog.class);
// Create Realization instance
realization = new PaymentProcessingRealization(
essence,
mockGateway,
mockDatabase,
mockLog
);
}
@Test
public void testProcessPayment_ValidPayment_ProcessesSuccessfully() {
// Arrange
PaymentRequest payment = createValidPaymentRequest();
CustomerHistory history = createNormalCustomerHistory();
GatewayResponse gatewayResponse = createSuccessfulGatewayResponse();
when(mockDatabase.getCustomerHistory(anyString()))
.thenReturn(history);
when(mockGateway.processPayment(anyDouble(), any(), anyString()))
.thenReturn(gatewayResponse);
// Act
PaymentResult result = realization.processPayment(payment);
// Assert
assertTrue(result.isSuccessful());
verify(mockDatabase).getCustomerHistory(payment.getCustomerId());
verify(mockGateway).processPayment(anyDouble(), any(), anyString());
verify(mockDatabase).storeTransaction(any(Transaction.class));
verify(mockLog).log(any(Transaction.class));
}
@Test
public void testProcessPayment_InvalidPayment_RejectsWithoutGatewayCall() {
// Arrange
PaymentRequest payment = createInvalidPaymentRequest();
// Act
PaymentResult result = realization.processPayment(payment);
// Assert
assertFalse(result.isSuccessful());
verify(mockGateway, never()).processPayment(
anyDouble(),
any(),
anyString()
);
verify(mockDatabase, never()).storeTransaction(
any(Transaction.class)
);
}
@Test
public void testProcessPayment_HighRiskPayment_QueuesForReview() {
// Arrange
PaymentRequest payment = createHighValuePaymentRequest();
CustomerHistory history = createNormalCustomerHistory();
when(mockDatabase.getCustomerHistory(anyString()))
.thenReturn(history);
// Act
PaymentResult result = realization.processPayment(payment);
// Assert
assertTrue(result.isPending());
verify(mockDatabase).queueForReview(payment);
verify(mockGateway, never()).processPayment(
anyDouble(),
any(),
anyString()
);
}
@Test
public void testProcessPayment_GatewayFailure_ReturnsFailedResult() {
// Arrange
PaymentRequest payment = createValidPaymentRequest();
CustomerHistory history = createNormalCustomerHistory();
GatewayResponse gatewayResponse = createFailedGatewayResponse();
when(mockDatabase.getCustomerHistory(anyString()))
.thenReturn(history);
when(mockGateway.processPayment(anyDouble(), any(), anyString()))
.thenReturn(gatewayResponse);
// Act
PaymentResult result = realization.processPayment(payment);
// Assert
assertFalse(result.isSuccessful());
verify(mockDatabase).storeTransaction(any(Transaction.class));
verify(mockLog).log(any(Transaction.class));
}
@Test
public void testGetPaymentStatus_ExistingTransaction_ReturnsStatus() {
// Arrange
String transactionId = "TXN-12345";
Transaction transaction = createCompletedTransaction();
when(mockDatabase.getTransaction(transactionId))
.thenReturn(transaction);
// Act
PaymentStatus status = realization.getPaymentStatus(transactionId);
// Assert
assertTrue(status.isFound());
assertEquals(TransactionStatus.COMPLETED, status.getStatus());
}
@Test
public void testGetPaymentStatus_NonExistentTransaction_ReturnsNotFound() {
// Arrange
String transactionId = "TXN-99999";
when(mockDatabase.getTransaction(transactionId))
.thenReturn(null);
// Act
PaymentStatus status = realization.getPaymentStatus(transactionId);
// Assert
assertFalse(status.isFound());
}
private PaymentRules createTestRules() {
// Create and configure test rules
return new PaymentRules();
}
private PaymentRequest createValidPaymentRequest() {
PaymentRequest payment = new PaymentRequest();
payment.setAmount(100.00);
payment.setCurrency("USD");
payment.setMethod(PaymentMethod.CREDIT_CARD);
payment.setCustomerId("CUST-001");
return payment;
}
private PaymentRequest createInvalidPaymentRequest() {
PaymentRequest payment = new PaymentRequest();
payment.setAmount(-50.00);
return payment;
}
private PaymentRequest createHighValuePaymentRequest() {
PaymentRequest payment = new PaymentRequest();
payment.setAmount(7000.00);
payment.setCurrency("USD");
payment.setMethod(PaymentMethod.CREDIT_CARD);
payment.setCustomerId("CUST-001");
return payment;
}
private CustomerHistory createNormalCustomerHistory() {
CustomerHistory history = new CustomerHistory();
history.setTransactionCount(50);
history.setAverageAmount(120.00);
return history;
}
private GatewayResponse createSuccessfulGatewayResponse() {
GatewayResponse response = new GatewayResponse();
response.setSuccessful(true);
response.setTransactionId("TXN-12345");
response.setStatus(TransactionStatus.COMPLETED);
return response;
}
private GatewayResponse createFailedGatewayResponse() {
GatewayResponse response = new GatewayResponse();
response.setSuccessful(false);
response.setErrorMessage("Insufficient funds");
return response;
}
private Transaction createCompletedTransaction() {
Transaction transaction = new Transaction();
transaction.setStatus(TransactionStatus.COMPLETED);
return transaction;
}
}
These integration tests verify that the Realization layer correctly coordinates between the Essence layer and infrastructure services. They use mocks for infrastructure components to avoid dependencies on actual databases or payment gateways, making the tests fast and reliable. The tests verify that the Realization layer calls the appropriate infrastructure methods in the correct order and handles both success and failure scenarios properly.
CHALLENGES AND CONSIDERATIONS
While LLMs provide significant benefits for CCA analysis and design, there are important challenges and limitations to consider.
First, LLMs can generate plausible but incorrect code. LLMs are trained on large datasets of existing code, which includes both good and bad examples. An LLM might generate code that looks correct but contains subtle bugs, security vulnerabilities, or performance issues. All LLM-generated code must be carefully reviewed by experienced developers who understand both the domain and the architectural principles.
Second, LLMs lack deep domain knowledge. While LLMs have broad knowledge across many domains, they lack the deep, specialized knowledge that domain experts possess. For example, an LLM might not understand the specific safety requirements of a medical device or the regulatory constraints of a financial system. Domain experts must review and validate LLM-generated designs to ensure they meet all domain-specific requirements.
Third, LLMs cannot make architectural trade-offs. Architecture involves making difficult trade-offs between competing concerns such as performance versus maintainability, flexibility versus simplicity, or cost versus reliability. LLMs can present options and explain trade-offs, but they cannot make the final decision about which trade-off is appropriate for a specific context. These decisions require human judgment based on business priorities, technical constraints, and organizational capabilities.
Fourth, LLM output quality depends on prompt quality. Crafting effective prompts requires skill and experience. Vague or ambiguous prompts lead to vague or inappropriate outputs. Architects must learn how to communicate effectively with LLMs, providing sufficient context and constraints while leaving room for creative solutions.
Fifth, LLMs may perpetuate existing biases and antipatterns. If an LLM has been trained on code that contains common antipatterns or outdated practices, it may reproduce those patterns in its generated code. Developers must be vigilant about identifying and correcting such issues.
Sixth, privacy and security concerns exist when using cloud-based LLMs. Sending proprietary code or sensitive requirements to a cloud-based LLM service may violate confidentiality agreements or expose intellectual property. Organizations should carefully consider which information can be shared with LLM services and may need to use on-premises LLM solutions for sensitive work.
Despite these challenges, LLMs remain valuable tools when used appropriately. They excel at automating routine tasks, generating boilerplate code, suggesting design alternatives, and identifying common patterns. By combining LLM capabilities with human expertise, software engineers can significantly improve their productivity and the quality of their CCA-based systems.
CONCLUSION
Large Language Models represent a powerful new tool for software architects and developers working with Capability-Centric Architecture. LLMs can assist in analyzing requirements to identify Capabilities, defining Contracts between Capabilities, generating skeleton implementations with proper layer separation, detecting architectural antipatterns, and producing comprehensive documentation. When combined with appropriate UML diagrams such as Component Diagrams for showing Capability dependencies, Class Diagrams for showing internal Capability structure, Sequence Diagrams for showing dynamic interactions, Use Case Diagrams for identifying functional requirements, Deployment Diagrams for showing physical distribution, Activity Diagrams for showing workflows, and State Machine Diagrams for showing entity lifecycles, LLMs enable architects to work more efficiently and produce higher-quality designs.
The key to successful use of LLMs in CCA is to treat them as assistants that augment human capabilities rather than replacements for human expertise. LLMs excel at pattern recognition, code generation, and documentation, but they lack the deep domain knowledge, contextual understanding, and judgment required for critical architectural decisions. By leveraging LLMs for routine tasks while applying human expertise to strategic decisions, software engineers can achieve the best of both worlds: the efficiency and consistency of automated assistance combined with the creativity and wisdom of experienced architects.
As LLM technology continues to advance, we can expect even more sophisticated assistance for architectural work. Future LLMs may be able to perform more complex analysis, suggest more nuanced trade-offs, and generate more complete implementations. However, the fundamental principles of CCA will remain relevant: organizing systems into cohesive Capabilities with clear Contracts, separating pure domain logic from infrastructure concerns, managing dependencies to prevent cycles, and planning for evolution from the beginning. By mastering these principles and learning to work effectively with LLM tools, software engineers can build systems that are maintainable, testable, and evolvable across the entire embedded-to-enterprise spectrum.
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