Properties of an Architectural Style
An architectural style can be described using four main properties:
Design Vocabulary
Defines the types of architectural elements used in the style.
Examples include:
- Component types
- Connector types
- Data elements
Configuration Rules
Define how architectural elements can be composed and connected.
These include the structural or topological constraints of the style.
Semantic Interpretation
Defines the meaning of compositions of the architectural elements.
Style-Specific Analysis
The constraints of a style can make certain architectural analyses possible.
Important Style Concepts
Layered Style
- Each layer exposes an interface to layers above it.
- A layer acts as a server to layers above.
- A layer acts as a client of layers below.
- Connectors are protocols of layer interaction.
Pipe and Filter Variations
- Pipelines
Linear sequences of filters. - Bounded pipes
Pipes with a limited amount of data. - Typed pipes
Pipes where data is strongly typed.
Rule-Based Style
The main components are:
- User interface
- Inference engine
- Knowledge base
The inference engine determines whether input is a fact/rule or a query.
Interpreter Style
An interpreter:
- Parses input commands.
- Executes the commands.
- Updates the interpreter state.
The style supports dynamically changing capabilities.
Mobile-Code Variants
- Code-on-demand
- Remote evaluation
- Mobile agent
Publish-Subscribe
- Subscribers register or deregister to receive specific messages or content.
- Publishers broadcast messages to subscribers.
- Communication may be synchronous or asynchronous.
- Subscribers may connect directly to publishers or through intermediaries.
Event-Based Style
- Components independently generate and consume events.
- Events are communicated through event buses.
- Components communicate with the event bus rather than directly with each other.
- Communication may be push-based or pull-based.
Peer-to-Peer Style
- State and behavior are distributed among peers.
- Each peer can act as either a client or server.
- Peers have their own state and control thread.
- Communication commonly uses network protocols.
- The topology can vary dynamically.
