1 CBSE Process: issues and Challenges From CBSE Landscape document chapter From

CBSEnet 2 BackgroundBackground CBSE is the process of building software systems from pre-fabricated software components Motivation Improving software quality and Reducing development costs However software component technology is still immature and poses many challenges for organisations intending to adopt it Poorly documented components Vulnerability risk Limited adaptability of components Limited interoperability across component technologies Component volatility Many of these problems can be mitigated by a better appreciation of the processes for developing component-based systems CBSE is the process of building software systems from pre-fabricated software components Motivation Improving software quality and Reducing development costs However software component technology is still immature and poses many challenges for organisations intending to adopt it Poorly documented components Vulnerability risk Limited adaptability of components Limited interoperability across component technologies Component volatility Many of these problems can be mitigated by a better appreciation of the processes for developing component-based systems

CBSEnet 3 CBSE Processes

CBSEnet 4 Development with reuse

CBSEnet 5 Development process The planning phase sets out: Justification, objectives, strategies (methods and and resources to achieve the development objectives) Tactics ( start and end dates, tasks with duration) for the development project The development phase implements the agenda set out in the planning phase The verification phase is intended to verify the extent of “fitness” of various component solutions The negotiation phase attempts to find an acceptable trade-off between the software components and system being built The planning phase sets out: Justification, objectives, strategies (methods and and resources to achieve the development objectives) Tactics ( start and end dates, tasks with duration) for the development project The development phase implements the agenda set out in the planning phase The verification phase is intended to verify the extent of “fitness” of various component solutions The negotiation phase attempts to find an acceptable trade-off between the software components and system being built

CBSEnet 6 Design for development with reuse Component-based system design Describes how the components that make up the system interact to deliver the desired functionality and, the appropriateness of particular components and services in different contexts Provides a good basis for performing impact analysis Component-based system design Describes how the components that make up the system interact to deliver the desired functionality and, the appropriateness of particular components and services in different contexts Provides a good basis for performing impact analysis

CBSEnet 7 Design process Need for formal mechanisms that allow the designer to define architectural elements and their relationships and to support their evolution through levels of abstraction (UML 2.0?, Catalysis, D’Souza ’98; ADLs Shaw, ‘96; Medvidovic ‘00) The design process starts with the partitioning of the system requirements (services and associated constraints) into logical “components” or “sub- systems” The initial partitioning is driven by architectural considerations (possibly supported by design patterns that lend themselves to those properties) Subsequent partitioning is subject to a negotiation process that must take into account business concerns, architectural considerations and software component considerations Need for formal mechanisms that allow the designer to define architectural elements and their relationships and to support their evolution through levels of abstraction (UML 2.0?, Catalysis, D’Souza ’98; ADLs Shaw, ‘96; Medvidovic ‘00) The design process starts with the partitioning of the system requirements (services and associated constraints) into logical “components” or “sub- systems” The initial partitioning is driven by architectural considerations (possibly supported by design patterns that lend themselves to those properties) Subsequent partitioning is subject to a negotiation process that must take into account business concerns, architectural considerations and software component considerations

CBSEnet 8 Management: Maintenance and extended development The maintenance and extended development of a component-based application poses many risks to the customer (Dean and Vidger ’99) Nature of the development process Application domain System design characteristics Choice of software components used Choice of software components used The maintenance and extended development of a component-based application poses many risks to the customer (Dean and Vidger ’99) Nature of the development process Application domain System design characteristics Choice of software components used Choice of software components used

CBSEnet 9 SummarySummary Component-based system development is a highly iterative process requiring simultaneous consideration of: The system context (system characteristics such as requirements, cost, schedule, operating and support environments), Capabilities of software components in the marketplace Viable architectures and designs We have identified the challenges and problems likely to be faced by component-based system developers The importance of verification has been emphasised and a discussion of the management challenges of component-based systems provided We have highlighted the importance of the process in mitigating the problems posed by CBD Component-based system development is a highly iterative process requiring simultaneous consideration of: The system context (system characteristics such as requirements, cost, schedule, operating and support environments), Capabilities of software components in the marketplace Viable architectures and designs We have identified the challenges and problems likely to be faced by component-based system developers The importance of verification has been emphasised and a discussion of the management challenges of component-based systems provided We have highlighted the importance of the process in mitigating the problems posed by CBD

CBSEnet 10

11 CompositionComposition Need for formal mechanisms to support system composition System composition proceeds by replacing abstract design level components with concrete ‘equivalents’ and integrating them Concrete components might be required to fulfil certain constraints (cost, architectural, resource etc ) before a replacement is allowed to proceed Support for adaptation For many systems there is need to repair a design “misfit” The accompanying integration process may make use of some "gluing technology", which may be unrelated to the components:  To provide an interface between components  To adapt incompatible components Need for formal mechanisms to support system composition System composition proceeds by replacing abstract design level components with concrete ‘equivalents’ and integrating them Concrete components might be required to fulfil certain constraints (cost, architectural, resource etc ) before a replacement is allowed to proceed Support for adaptation For many systems there is need to repair a design “misfit” The accompanying integration process may make use of some "gluing technology", which may be unrelated to the components:  To provide an interface between components  To adapt incompatible components

CBSEnet 12 VerificationVerification Component and system testing is a critical aspect of component-based development Black-box nature of components Perception of quality may vary Extraneous features Component and system testing is a critical aspect of component-based development Black-box nature of components Perception of quality may vary Extraneous features

CBSEnet 13 Testing regimes To address these problems, component- testing regimes should serve the following aims: DiscoveryVerification Fitness for purpose MaskingAdequacy To address these problems, component- testing regimes should serve the following aims: DiscoveryVerification Fitness for purpose MaskingAdequacy

CBSEnet 14 Trust as mechanism for verification Models of trust Contractual schemes are intended to provide cover against the effects of unsatisfactory or unexpected performance of a particular product Certification schemes are based on the belief that certified products have undergone rigorous testing and found to be fit for use (conform to certain quality standards) Experience-based schemes rely on reputed trust Local evaluation schemes strive to establish ‘demonstrated trust’. May be based on  Detailed evaluation  Self certification Models of trust Contractual schemes are intended to provide cover against the effects of unsatisfactory or unexpected performance of a particular product Certification schemes are based on the belief that certified products have undergone rigorous testing and found to be fit for use (conform to certain quality standards) Experience-based schemes rely on reputed trust Local evaluation schemes strive to establish ‘demonstrated trust’. May be based on  Detailed evaluation  Self certification