Component Based Systems Analysis

1. IS7 VT99 Component Based Systems Analysis Introduction

2. Why Components? • Development alternatives: • In-house software • Standard packages • Components 60% of the functionality in a typical information system is the same for all organisations (IBM)

3. What is a Component? • “A component is a piece of software small enough to create and maintain, big enough to deploy and support and with standard interfaces for interoperability” (Jed Harris) • Components are executable

4. Component Models • Standard specification of how components should behave in a given environment • Versioning • Open tool palettes • Configuration management • Event notification • Metadata and introspection • Licensing

5. Levels of Components Insurance Telecom Aerospace Subscriber Telephone service Domain Components General Business Components Customer, Product, Order, Currency Technical Components GUI components Security services

6. Component Based Development Supply - Build new - Wrap existing - Buy Consume - Assemble applications Manage - Publish - Subscribe - Catalogue - Browse

7. Objects and Components Analysis Design Construction Object oriented Component based A component does not have to be an object

8. Client/Server Architecture A server providing services A client requesting services ATMs Thin and fat clients

9. Advantages of Client/Server • Scalability • Horizontal, more clients • Vertical, more powerful server • Dedicated servers • Shared resources • Maintenance • Server centrally • Client locally

10. Three Level Architecture User interface provided via a browser Presentation Java servlets running on a server Application logic Data Data served from a DBMS Handles data from different sources within client/server

11. Distributed Objects • Objects encapsulate data and operations • Ordinary objects • Reside in a single program • Cease to be separate entities after compilation • Distributed objects • Reside anywhere on a network • Exist as physical standalone entities • Accessible by other objects

12. Middleware • Distributed software for supporting interaction between client and server; including client API, network transfer, and server response • Database middleware: ODBC, JDBC, … • Internet middleware: HTTP, … • Object middleware: CORBA, COM/DCOM, Enterprise JavaBeans, ...

13. OMG Object Management Architecture Application objects Common facilities Object Request Broker Object services

14. Architectural Patterns • Context • Designing a living room • Problem • Making people feel comfortable • Forces • People want to sit down • People want to be close to the light • Solution • Put a sitting place close to the windows

15. Design Patterns • Context • Developing software with a human-computer interface • Problem • Interfaces vary often • Forces • Easy to modify the interface • Modifying the interface should not impact the application logic • Solution • Model-View-Controller

16. A Design Pattern - MVC Model core data notify getData View myModel display update Controller myView handleEvent update

17. Properties of Patterns • Address recurring problems • Document well-proven experience • Specify abstract solutions

18. Analysis Patterns Person Employment Organisation Period of Time A person is employed in an organisation for a period of time.

19. Analysis Patterns Person Management Role Organisation Period of Time A person has a certain management role for a period of time.

20. Analysis Patterns Marriage Person Period of Time Two people are married for a period of time.

21. Analysis Patterns One party is accountable to another party for something for a period of time. Accountability type Organisation Accountability Period of Time Organisation Person

22. Course contents Component models JavaBeans SanFrancisco Analysis patterns Fowler DOT Java Servlets EJB CORBA COM/DCOM