Architectural Styles - Finale

Transcription

1 Material and some slide content from: - Emerson Murphy-Hill - Software Architecture: Foundations, Theory, and Practice - Essential Software Architecture Architectural Styles - Finale Reid Holmes Lecture 7 - Tuesday, October

2 Architectural Styles [TOPOLOGY FROM TAILOR ET AL.] Language Based Layered Dataflow Peer-to-Peer Objectoriented Client Server Pipe-and-Filter Main program & Subroutines Virtual Machine Shared Memory Interpreter Implicit Invocation Rule-based Interpreter Batchsequential Publishsubscribe Blackboard Mobile code Event-based

3 Implicit invocation In contrast to other patterns, the flow of control is reversed. Commonly integrate tools in shared environments. Components tend to be loosely coupled. Often used in: UI applications (e.g., MVC, MVP). Enterprise systems (e.g., WebSphere)

4 Style: Event-based

5 [TAILOR ET AL.] Style: Event-based Independent components asynchronously emit and receive events. Components: Event generators / consumers. Connections:? Data elements: Events. Topology:?

6 [TAILOR ET AL.] Style: Event-based Variants: May be push or pull based (with event bus). Qualities:? Typical uses: User interfaces. Widely distributed applications (e.g., financial markets, sensor networks). Cautions:?

7 Style: Publish-subscribe

8 [TAILOR ET AL.] Style: Publish-subscribe Subscribers register for specific messages or content. Publishers maintain registrations and broadcast messages to subscribers as required. Components:? Connections: Typically network protocols. Data elements: Subscriptions, notifications, content. Topology: Subscribers connect to publishers either directly or through intermediaries.

9 [TAILOR ET AL.] Style: Publish-subscribe Variants: Complex matching of subscribers and publishers can be supported via intermediaries. Qualities:? Typical uses: News, GUI programming, network games. Cautions: Scalability to large numbers of subscriber may require specialized protocols.

10 Interpreter Interpret commands on the fly. Based on a virtual machine produced in SW. Components are the program, its data, its state, and the interpretation engine. e.g., Java Virtual Machine. JVM interprets Java bytecode).

11 Style: Interpreter

12 [TAILOR ET AL.] Style: Interpreter Update state by parsing and executing commands. Components:? Connections: Components tightly bound; uses procedure calls and shared state. Data elements: Commands. Topology: Tightly coupled three-tier.

13 [TAILOR ET AL.] Style: Interpreter Qualities:? Typical uses: End-user programming. Cautions: May not be performant.

14 Style: Mobile code

15 [TAILOR ET AL.] Style: Mobile code Code and state move to different hosts to be interpreted. Components:? Connections: Network protocols. Data elements: Representations of code, program state, data. Topology: Network.

16 [TAILOR ET AL.] Style: Mobile code Variants: Code-on-demand, remote evaluation, and mobile agent. Qualities: Dynamic adaptability. Typical uses:? Cautions: Security. Transmission costs. Network reliability.

17 Peer-to-peer

18 [TAILOR ET AL.] Style: Peer-to-peer State and behaviour are distributed among peers that can act as clients or servers. Components: Peers (aka independent components). Connections: Network protocols. Data elements: Network messages. Topology:?

19 [TAILOR ET AL.] Style: Peer-to-peer Qualities:? Typical uses: When information and operations are distributed. Cautions: Security. Time criticality.

20 Architectural representations Characteristics of representations: Ambiguity:? Accuracy: Correct within tolerances. Precision: Exact but not necessarily correct. Architectural models can be overwhelming. Model individual concerns with unique views. Views overlap and can be consistent on inconsistent.

21 Statechart diagram More formal description of system behaviour. Poor mapping between states and components.

22 Component diagram Captures components and relationships. Required and provided APIs explicitly recorded.

23 Deployment diagram Provide mapping between physical devices.

24 Sequence diagram Focus on inter-component collaboration. Capture behaviour for specific scenarios.

25 Activity List the major components and connectors for your system. Create a basic statechart for your system. Create a rough component and deployment diagram for two different architectures. Choose the arch that you think is best for your task; you will motivate this decision to me. Perform an inter-group architectural review; be critical.