1. HW2 INTRODUCTION CSCI-578 Spring 2013

2. 2 Implicit Invocation  Indirectly or implicitly calls to methods and interfaces in response to an event or a received message  Publish/Subscribe  Event-based

3. 3 Publish/Subscribe Subscribers register/deregister to receive specific messages or specific content. Publishers broadcast messages to subscribers either synchronously or asynchronously.

4. 4 Pub-Sub LL Software Architecture: Foundations, Theory, and Practice; Richard N. Taylor, Nenad Medvidovic, and Eric M. Dashofy; © 2008 John Wiley & Sons, Inc. Reprinted with permission.

5. 5 Event-Based Style  Independent components asynchronously emit and receive events communicated over event buses  Components: Independent, concurrent event generators and/or consumers  Connectors: Event buses (at least one)  Data Elements: Events – data sent as a first-class entity over the event bus  Topology: Components communicate with the event buses, not directly to each other.  Variants: Component communication with the event bus may either be push or pull based.  Highly scalable, easy to evolve, effective for highly distributed applications.

6. 6 Event-based LL Software Architecture: Foundations, Theory, and Practice; Richard N. Taylor, Nenad Medvidovic, and Eric M. Dashofy; © 2008 John Wiley & Sons, Inc. Reprinted with permission.

7. DEB Systems  Typically based on message-oriented middleware (MOM)  Components via implicit invocation  Producers and consumers  Message interfaces  Message sink  Message source

8. Message Types  Nominal  Mapped to statically checkable PL types  Subject-Based  “/Weather/Germany/Berlin”  Attribute-Based  Key-Value Pairs

9. Attribute-based Messages  Key-value pairs  Key: Name, Value: PicUpdate  Key: Sum, Value: 50  Attribute Reading  Attribute Adding or Modifying

10. What Makes It Hard?  Ambiguous Interfaces  State-based dependencies void onMessage(Message msg) { String type = msg.getJMSType(); if (type.equals( “On/Off”) ) {... } else if (type.equals(“PicRequest”)) {... } } MessageMessage DispatchDispatch

11.  Inter-Component Message Dependence Classifying Message Dependences

12.  Inter-Component Message Dependence  Intra-Component Dependence  Control-Flow-Based

13.  Inter-Component Message Dependence  Intra-Component Dependence  Control-Flow-Based  Data-Flow-Based Classifying Message Dependences

14. HW2  Maintenance Tasks  Description of changes  Message-based dependencies  Why  The applications and MOM platforms  Some tools

15. STOX in general  Monitoring Stock changes and alerting customers  Three Important part:  Trigger List Absolute limit: Triggered if the price of the respective stock is either below or above a specified range Relative limit: Triggered if the price of a given stock has increased or decreased a given number of percentages within a given time interval.  Portfolio depicts detailed information about the stocks that a user currently holds  Charts visualize the price of a certain stock over time

16. STOX Architecture

17. 17 KLAX Software Architecture: Foundations, Theory, and Practice; Richard N. Taylor, Nenad Medvidovic, and Eric M. Dashofy; © 2008 John Wiley & Sons, Inc. Reprinted with permission.

18. 18 KLAX in C2 Software Architecture: Foundations, Theory, and Practice; Richard N. Taylor, Nenad Medvidovic, and Eric M. Dashofy; © 2008 John Wiley & Sons, Inc. Reprinted with permission.

19. 19 C2 Style An indirect invocation style in which independent components communicate exclusively through message routing connectors. Strict rules on connections between components and connectors induce layering.

20. 20 C2 Style (cont’d)  Components: Independent, potentially concurrent message generators and/or consumers  Connectors: Message routers that may filter, translate, and broadcast messages of two kinds: notifications and requests.  Data Elements: Messages – data sent as first-class entities over the connectors. Notification messages announce changes of state. Request messages request performance of an action.  Topology: Layers of components and connectors, with a defined “top” and “bottom”, wherein notifications flow downwards and requests upwards.

21. c2.fw framework  MOM platform that KLAX is built from  Enforces C2 Style  Includes C2 components C2 connectors Messages

22. SPECjms2009  JMS-based MOM  TextMessages, ObjectMessages, StreamMessages or MapMessages  Pub/sub (topics) vs. P2P messages (queues)  Performance benchmarks  Supply chain of a supermarket company  Documentation provided

23. The Supply Chain Simulation

24. Use of Regular Expressions  AbsLimitEvent*

25. Use of Regular Expressions(Cont.)  publish(.*AbsLimitEvent.*)

26. Unix Commands  find  Finds files and directories  xargs  Reads from standard input  Builds arguments  Calls command  grep  Regular expressions

27. Example