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Component Development

Component Development. Component Based SW Engineering. Summary of contents. Introduction Why do we need a new approach? Lifecycle process models Basic activities Component Development Building from components Develop new components Language and environment Theory meets practice

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Component Development

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  1. Component Development Component Based SW Engineering

  2. Summary of contents • Introduction • Why do we need a new approach? • Lifecycle process models • Basic activities • Component Development • Building from components • Develop new components • Language and environment • Theory meets practice • Conclusions

  3. 1. Introduction 1. Introduction • Why do we need a new approach? • Technology is not enough • Need to change the development & life cycle • Lifecycle process models • Sequential: waterfall, V model Þ sequential activities … … • Long development time • Bigger systems + many stakeholders

  4. 1. Introduction 1. Introduction (2) • Evolutionary: iterative, spiral modelÞ parallel activities • Smaller systems + time to market • Basic Activities • Requirement analysis & specification • System & software design • Implementation + unit testing • System integration • Verification & Validation • Maintenance • Disposal

  5. 2. Component development 2. Component development • CBSE challenges • Similar to those typical of software engineering • Known methods, principles, tools are still valid. But… • 2 different processes • Building a system from existing components • Develop new and reusable components • Building a system FROM components • The main idea behind CBSE! • FOCUS: find & evaluate components • No “classic” unit design/development/testing • Effort on locating & adapting components

  6. 2.1 Building from components 2.1 Building FROM components • A new V model Maintenance Requirement System test No unit design/ dev./testing System design System integr. Select Adapt Test • Simplistic! What if: • No components to select • Adaptation cost is too high • Malfunction during maintenance Evaluate Find

  7. 2.1 Building from components 2.1 Building FROM components (2) • Component approach affects the entire life cycle! • Requirements: if not fulfilled by existing components… • Plan to develop new component or… • (Re)Negotiate requirements • System design: driven by chosen component model/technology Requirements System design Inspect Implementation… Inspect Component pool Available components

  8. 2.1 Building from components 2.1 Building FROM components (3) • Implementation • Select components • Connect components + implement new functions: glue code • Connected components: a new concept of unit • (Unit) Testing • Existing component: already tested in isolation • Test connected componentsÞ testing glue code Integration… …Design Select Test Adapt Component pool

  9. 2.1 Building from components 2.1 Building FROM components (4) • System integration • Deploy the component in existing framework • Download & register new component • Verification and validation • Standard techniques but… • Locate errors exhibited by black-box components • Errors lie in other components Þ check contractual interfaces • 3 different phases of verification • Component in isolation • Component in an assembly • System with deployed components

  10. 2.1 Building from components 2.1 Building FROM components (4) • Support & maintenance • A new component can be deployed • Newer versions must be tested and integrated • Change glue code } V&V (again…) Maintenance Deployment …System test Select Test Adapt • Conclusions • Less effort on implementation • Greater costs of verification & testing

  11. 2.2 Building new components 2.2 Building NEW components • Develop new components: • Follow an arbitrary (modified) process model • Not only functionality but also REUSE! Additional functions Generality Test different configurations REUSE Flexibility Portability More formal documentation Understanding Well trained team 3rd party integration Adapters … …

  12. 2.2.1 COP 2.2.1 Component oriented programming (COP) • A new methodology, not fully addressed • Support of: • Polymorphism • Modular encapsulation • Late binding & loading • Type/module safety • Works within a single component • Interactions between components: not covered • Connection oriented programming

  13. 2.2.1 COP 2.2.1 COP: Methodology and problems to face • Specification of provided/required interface(s) • Comprehensive of non functional requirements: interaction protocols, WCET, memory… • Consistence during events propagation • Multithreading: • Avoid deadlock by transactional programming • Queue invocations and process it in a defined moment Caller Called post request get request to fulfill Queued invocations

  14. 2.2.1 COP 2.2.1 COP: Problems to face (2) • Limits of (most) available languages • Avoid implementation inheritance: clumsy if minor adaptation is needed • Group method in many little interfaces • (Automatically generated) forwarder class • Template (compile-time code generation) • Proxy classes and reflection (Java, C#) • Provide nutshell class: impl. inheritance of whitebox classes abstract class Nutshell implements I{ ClassToForward c = new ClassToForward(); //forward each method m() to c.m() }; class MyClass extends Nutshell{ //override only methods of interest };

  15. 2.2.1 COP 2.2.1 COP: Problems to face (3) • Accessibility of provided interface • No languages distinguish pure outgoing and ingoing interfaces (apart Component Pascal…) • Dangerous to call methods from outside a protected domain package java.lang; class MyClass{ … void m(AnotherClass obj){ obj.finalize(); } … } This should be done by the gc only!

  16. 2.3 Language and environment 2.3 Language and environment • Programming language • Need for polymorphism, late binding, encapsulation, safety (COP) Þ use OO languages (at the moment…) • C, C++, Cobol, Eiffel, Smalltalk lack something • Java, C#, Ada 95(2005) are reasonable choice • Java: too weak package system • C#: events, connection, module access protection (assembly) • Environment: choose a framework carefully • “Divorce” is almost impossible • Difficult to combine different frameworks • Migration is even harder…

  17. 2.4 Theory meets practice 2.4 Theory meets practice • Develop a new system • Pure top-down: not meet existing component • Pure bottom-up: not meet requirements • Use existing & develop new components • Separate system and components dev. across teams • Synchronize teams • Late discovery of errors: insufficient documentation • Which component should satisfy a requirement? • Difficult to perform processes independently • Need for a structured organization focusing on: • Architectural issues • Non productive processes (testing, quality)

  18. 3. Conclusions 3. Conclusions • Technology is not enough • Change the development and life cycle process • 2 distinct processes: • Building from components • Focus on selecting existing components and testing • A new V model • Building new components • Focus on reuse (generality, flexibility, quality…) • Component oriented programming • Real project:componentreuse & development • Effort on verification and quality assurance • Structured organization

  19. Questions ?

  20. Additional references Additional references • “Component Development for the Java platform” by Stuart Dabbs Halloway, ed. Addison Wesley • “Software Engineering Body Of Knowledge” (SWEBOK), available at www.swebok.org • The Catalysis method: www.catalysis.org

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