Subtopics: 1. Frameworks :Reusable systems 2. Design Patterns 1

F RAMEWORKS : REUSABLE SYSTEMS What are re-use able systems?  Reuse: Reuse can be defined as adapting to an existing system.  It facilitates software development.  Frameworks are a software technology, that promotes reuse. 2

W HAT IS S OFTWARE R EUSE ?  It is the process of implementing or updating software systems using existing software assets.  Software assets, include all software products, from requirements to specifications & designs.  Anything that is produced from a software development effort can be reused. 3

W HY R EUSE S OFTWARE ?  Reusable means developing software that is understandable & flexible enough to be used in a variety of systems.  It avoids redeveloping software.  Facilitates the increase of productivity, quality, and reliability, and the decrease of costs and implementation time. 4

Types Of Reuse Standard Designs Expertise Complete Applications Frameworks Classes & Procedures 5

P ROS & C ONS OF SOFTWARE REUSE : Efficiency Standardization Debugging Profit earning Mismatch: Design may not completely match your system. Expense: Some components maybe too expensive for the project’s budget. PROS:CONS: 6

1. F RAMEWORKS :  Introduction to frameworks  Components of a framework  Types of frameworks  Object-Oriented frameworks  Example 7

I NTRODUCTION :  Framework :  Frameworks promote re-usability.  Provides common facilities which can be applied to various application programs. 8 A framework is a reusable software that provides a generic solution to a generalized problem.

P RINCIPLE BEHIND A FRAMEWORK :  They are different from other subsystems, since they are intrinsically incomplete.  This means they comprise of classes & methods which are either undeveloped or missing. 9 “identify the common design elements & develop software that implements these design elements in a useful way.”

10 Elements of a Framework SLOTS: Missing parts Filled in by developer to suit the system. Increases complexity. HOOKS: Similar to slots Optional for the developer. API: Set of services provided by frameworks. Consists of useful methods (functions).

T YPES OF FRAMEWORKS : 1. Provides general application facilities to be used by large no. of applications. 2. It is a single API. 3. Larger no. of slots and hooks, since implementation is more general &not specific. 4. Produces complexity in the development process. 1. Provides general application facilities to be used by specific classes only. 2. Comprised of several horizontal frameworks. 3. Fewer slots &hooks since implementation is specific. 4. Allows easy development. HORI ZONTA L VERTICA L 11

12 application Horizontal framework Vertical framework Services offered by the framework Code to be provided to adapt the framework to the needs of the application slot hook Fig: Horizontal & Vertical Framework

E XAMPLE : L IBRARY M ANAGEMENT  Problem Definition: Design a framework, so that different libraries would be able to adapt to, meet their needs. List the kind of facilities you want to provide, if you were to design such a framework. In what way do libraries differ such that they would want to use a framework rather than a complete application.? 13

S OLUTION : 1. User interface for standard searches(browsing). 2. Basic classes for books, clients, &their common operations. 3. Methods that store the user info. Like address etc..i.e. common data. 1. Kind of info kept about each member. 2. Rules of issuing book & fine schemes. 3. Specialized items that can be issued from the library. 4. Security mechanisms. 5. Integration of the system with other online libraries or books database. Common FactorsDifferentiating Factors 14

15 O BJECT - ORIENTED FRAMEWORKS : Developer Concrete Class Abstract Classes Subclass: Method1(); Method2(); creates inheritance Method1(); Method2(); Only SLOTS Actual methods

2:- I NTRODUCTION TO D ESIGN PATTERNS 16

P ATTERNS :  Patterns are recurring aspects of designs.  Used to create hierarchies of instances, i.e. General hierarchy. 17 “ A pattern is the outline or a reusable solution to a general problem encountered in a particular context.”

18 Anti patterns References Related Patterns Context Forces Problem Solution A good Pattern

A GOOD PATTERN SHOULD …….  Have a name.  Simple diagram, described in a narrative style.  The general situation.  Acknowledgements of contributors.  Recommended solution to the problem.  Issues to be considered while solving.  Main difficulty to be tackled. 19

20 TYPES Singleton Observer Adapter Facade Proxy

T HANK YOU 21 L.L.Britto,XIE,TE-I.T