Software Architecture Classification for Estimating the Costs of COTS Integration Yakimovich, Bieman, Basili; icse 99

Contents A set of variables for cost estimation of COTS integration A classification scheme of software architecture with respect to COTS integration

Techniques for COTS integration Change the component being integrated. Possible if source code is available, etc Use glueware = integration software. It is software that provides proper interface for the component (like wrappers) or serves as a mediator. >> Both techniques can lower system quality.

Interaction Protocol Mismatch Mismatch between assumptions by component on interaction with the environment and assumptions of the system. 4 types of interactions: –Component-platform interactions –Component-hardware interactions –Component-user interactions –Component-software interactions

Continue Component-platform interactions: on OS, CPU, etc. Component-hardware interactions: reading from specified ports, etc. Component-user interactions: user interface, language, etc

Component-software interactions Assumptions about nature of components: infrastructure, control model, data model. Assumptions about nature of connectors: protocols, data model. Assumptions about the global architecture: topology, etc Assumptions about the construction process

Variables to represent assumptions Component packaging Type of control Type of information flow Synchronization Binding A=B; Values are equal. A>=B; The value of A is greater than B. A=< B, The value of A is greater than B. A ~ B, A and B are not comparable

Component Packaging Definition: How a component is packaged for integration into a system. Values: Linkable vs independent.

Type of Control Definition: How a system provides control flow to its components. Values: Centralized, decentralized, no assumption.

Information Flow Definition: What type of information flows between components. Values: Control flow (invocation of some routines), data flow (exchange of data as message passing, shared memory), mixed (accepts both and can convert).

Synchronization Definition: Whether or not a component blocks when waiting for a response. Values: Synchronous, Asynchronous.

Component Binding Definition: How components are attached to connectors and how the participants in an interaction are determined. Values: static (predetermined), dynamic (compile time or run- time), mixed.

Software System Classification Pipes and filters Main program and subroutine OO systems Communicating process Event systems Blackboards C2 architectural style CORBA COM

Pipes and Filters Filters have input and output. Pipes are connectors. Packaging: not relevant. Control: not relevant. Information flow: data. Synchronization: not relevant. Binding: dynamic.

Main Program and Subroutines Components are procedures and functions. Connectors are calls between them. Packaging: not relevant. All linked together. Control: centralized. Information flow: control. Synchronization: synchronous. Binding: static.

OO Systems Components are objects. Connectors are invocation of objects. Packaging: not relevant. Control: usually centralized. Information flow: control. Synchronization: synchronous. Binding: dynamic.

Communicating Process Components are independent processes. Connectors are messages, RPC, shared memory, etc. Packaging: not relevant. Control: decentralized. Information flow: not relevant (in fact both). Synchronization: not relevant. Binding: not relevant.

Event systems A component register for an event and is called back. Packaging: not relevant. Control: decentralized. Information flow: control. Synchronization: not relevant. Binding: dynamic.

Blackboards Components are blackboards that stores the state of the system and other components have access to it. Actions are triggered by specific states. Packaging: not relevant. Control: not relevant. Information flow: data. Synchronization: not relevant. Binding: static. Everything is attached to the blackboard.

C2 Architectural Style An OO framework with few assumptions. Limitations: Message-based communication (provides wrappers as well), layered architecture. Packaging: depends on whether the language is supported. Control: all types. Information flow: data. Synchronization: all types. Binding: dynamic.

CORBA For distributed OO architectures. Language and platform independent. Packaging: depends on whether the language is supported. Control: decentralized. Information flow: control (like RPC). Synchronization: all types. Binding: run-time dynamic using Naming service.

COM Binary, objects make RPC, language independent, multiple interfaces for an object. Packaging: depends on whether the language is supported. Control: decentralized. Information flow: control (like RPC). Synchronization: all types. Binding: run-time dynamic using QueryInterface.

Estimating Integrating Costs Fine the interaction vector of the system (Vs) and the COTS (Vp) and compare: –Vs=Vp; match. –Vs >= Vp; still compatible. –Vs <= Vp; some assumptions are not compatible.A common upper element Vc is found and the cost of modifying the system and the COTS towards Vc is estimated. Example in the article