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Chapter 1 Introduction

Chapter 1 Introduction. Major Topics. Define COP and its major objectives Discuss the importance of COP Define components and their characteristics Distinguish hardware components and software components Investigate the differences between OOP and COP

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Chapter 1 Introduction

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  1. Chapter 1 Introduction Component Oriented Programming

  2. Major Topics • Define COP and its major objectives • Discuss the importance of COP • Define components and their characteristics • Distinguish hardware components and software components • Investigate the differences between OOP and COP • Introducing component-based software engineering Component Oriented Programming

  3. Component • Dictionary definition • A unit of, part of a model • Hardware components • Software components • Differences? Component Oriented Programming

  4. What is a component? (1) • A component is a nontrivial, nearly independent, and replaceable part of a system that fulfills a clear function in the context of a well-defined architecture. A component conforms to and provides the physical realization of a set of interfaces. (Philippe Krutchen, Rational Software) 2. A runtime software component is a dynamically bindable package of one or more programs managed as a unit and accessed through documented interfaces that can be discovered at runtime. (Gartner Group) Component Oriented Programming

  5. What is a component? (2) 3. A software component is a unit of composition with contractually specified interfaces and explicit context dependencies only. A software component can be deployed independently and is subject to third-party composition. (Clemens Szyperski) 4. A business component represents the software implementation of an “autonomous” business concept or business process. It consists of the software artifacts necessary to express, implement, and deploy the concept as a reusable element of a larger business system. (Wojtek Kozaczynski, SSA) Component Oriented Programming

  6. What is a component? (3) 5. A reusable part of software, which is independently developed, and can be brought together with other components to build larger units. It may be adapted but may not be modified. A component can be, for example, a compiled code without a program source, or a part of a model and/or design. --- D'Souza and Wills Component Oriented Programming

  7. What is a component? (4) 6. A software component is a software element that conforms to a component model and can be independently deployed and composed without modification according to a composition standard. --- Councill and Heineman Component Oriented Programming

  8. What are in common? • A piece of software • Independently deployable • Composable • Self-contained • Reusable • A set of interfaces provided to, or required from the environment. • An executable code, which can be coupled to the code of other components via interfaces. Component Oriented Programming

  9. What are the differences? • These definitions begin from the consideration of CBSE from different viewpoints and focus on different aspects of software engineering such as: • Different phases (design, implementation and run-time phases) • Business aspects • Executable or not • Architectural issues Component Oriented Programming

  10. Implications of Szyperski’s definition • The following implications arise as a result of Szyperski’s definition: • For a component to be deployed independently, a clear distinction from its environment and other components is required. • A component must have clearly specified interfaces. • The implementation must be encapsulated in the component and is not directly reachable from the environment. Component Oriented Programming

  11. Implications of Councill & Heineman’s definition • A software component simply cannot be differentiated from other software elements by the programming language used to implement the component. • The difference is in how software components are used. • The definition of Software components depends on the underlined component model. Component Oriented Programming

  12. What is CBSE • CBSE: Component-Based Software Engineering • How to create reusable components • How to create software products with reusable components • Analysis, Design, Programming, Testing, Maintenance of component-based software • Requirements, Specification, Provisioning, Assembly of component-based software • COP: Component-Oriented Programming Component Oriented Programming

  13. Why CBSE? • The simplest answer: components are the way to go because all other engineering disciplines introduced components as they became mature & still use them. • Use component paradigm to simulate “Software Integrated Circuit” to resolve software crisis. • “Object orientation has failed but component software is succeeding” Udell, 1994 • Object technology does not include the notions of independence or late composition, mostly used to construct monolithic application. Configuring and integrating an individual object into some given system is not normally possible. • Object technology tends to ignore the aspects of economies and markets. Today only small amount of catalogs of class, class libraries, and frameworks exist. • Components are independent units of deployment! Component Oriented Programming

  14. Commonality and Difference • SP (Structured Programming) • OOP (Object-Oriented Programming) • COP (Component-Oriented Programming) • What are common? • What are different? Component Oriented Programming

  15. Component Oriented Programming

  16. COP vs OOP and SP • Other differences? • Identify at least one more difference. Component Oriented Programming

  17. Composability • Software entity and its ability of being integrated with other entities • SP – functions, procedures: low • OOP – classes, objects: high • COP – components: very high Component Oriented Programming

  18. The Interchangeability • SP: Two different implementations can never be interchangeable. • OOP: Two different objects implementing the same specification are interchangeable. • COP: Two different components with different specifications are interchangeable as long as they satisfy those interface requirements for all client components. Component Oriented Programming

  19. Component Goals • If you are asked to name three goals for using component technology, what are they? • Write down your wish list for CBD or COP Component Oriented Programming

  20. Component Goals • Conquering complexity • Managing change • Reuse Component Oriented Programming

  21. Conquering Complexity • We are living in a complex world! • “The world produces between 1 and 2 exabytes of unique information per year, which is roughly 250 megabytes for every man, woman, and child on earth. An exabyte is a billion gigabytes, or 1018 bytes.” • http://www.sims.berkeley.edu/research/projects/how-much-info/summary.html Component Oriented Programming

  22. Component Oriented Programming

  23. Managing Change • Change is inherent in software engineering. • The user requirements change, specifications change, personnel change, budgets change, technology change, etc. etc. • This means building for change, design for change, is necessary. • It is important to place primary emphasis during architecture and design on the dependencies between the components, and the management of those dependencies. Component Oriented Programming

  24. Reuse • Design and implement something once and use it over and over again in different contexts. • This will realize large productivity gains, taking advantage of best-in-class solutions, the consequent improved quality, and so forth. • Develop for reuse, and develop with reuse Component Oriented Programming

  25. CBSE • Component-Based Software Engineering • CBSE = COA + COD + COP + COM • Two key activities: • Development for reuse • Development with reuse Component Oriented Programming

  26. Component Forms • Component specification • Component interface • Component implementation • Installed component • Component object Component Oriented Programming

  27. Component Specification • The specification of a unit of software that describes the behavior of a set of Component Objects and defines a unit of implementation. • Behavior is defined as a set of Interfaces. A Component Specification is realized as a Component Implementation. Component Oriented Programming

  28. Component Interface • A definition of a set of behaviors that can be offered by a Component Object . Component Oriented Programming

  29. Component Implementation • A realization of Component Specification, which is independently deployable. • This means it can be installed and replaced independently of other components. It does not mean that it is independent of other components – it may have many dependencies. It does not necessarily mean that it is a single physical item, such as a single file. Component Oriented Programming

  30. Installed Component • An installed (or deployed) copy of a Component Implementation. • A Component Implementation is deployed by registering it with the runtime environment. This enables the runtime environment to identify the Installed Component to use when creating an instance of the component, or when running one of its operations. Component Oriented Programming

  31. Component Object • An instance of an Installed Component. • A runtime concept. • An object with its own data and a unique identity. • The thing that performs the implemented behavior. An Installed Component may have multiple Component Objects (which require explicit identification) or a single one (which may be implicit). Component Oriented Programming

  32. Summary • A component is a reusable software element confirms to a component model • Software engineering has gone through SP and OOP towards COP • There are three goals for COP • Interface and independently deployable are the unique features of COP comparing to OOP and SP • There could have many different forms of components Component Oriented Programming

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