Invisibility is an inherent and significant problem in the task of developing large software systems. There are no direct solutions to this problem

There are four fundamental aspects of use and reuse in building systems from components: conceptualization, retrieval, selection and correct use. The most important barrier to use and reuse, initially at least, is that of conceptualization. The Inscape Environment is a specification-based software development environment (SDE) integrated by the constructive use of formal interface specifications. The purpose of the formal interface specifications and the semantic interconnections (created and maintained as software is built and evolved) is to make explicit the invisible semantic dependencies that result in conventionally built systems. The important ingredient provided by Inquire in conceptualization, retrieval, selection and use is the set of predicates that describe the semantics of the elements in the interface. These predicates define the abstractions that are germane to the module interface and describe the properties of data objects and the assumptions and results of operations i...

Given a software library whose components are represented by formal specifications, we distinguish between two types of retrieval procedures: exact retrieval, whereby, given a query K, we identify all (and only) the library components that are correct with respect to K; approximate retrieval, which is invoked in case exact retrieval fails, and which (ideally) identifies the library components that minimize the required adaptation effort (once such a component is retrieved, the effort of adapting it to satisfy query K is minimal over the set of all the components of the library). To this effect, we define four measures of functional distance between specifications, and devising algorithms that minimize these measures over a structured set of components; then we discuss to what extent these measures can be used as predictors of adaptation effort. Correspondence author. 1 Exact Retrieval and Approximate Retrieval Software libraries are repositories where software components can be ...

A key component in a reuse-oriented software development environment is an appropriate software repository. We present a repository system which supports the entire software development life-cycle, providing for the integrated and consistent representation, organization, storage, management and presentation of the various aspects of reusable artifacts. The system can support multiple development and representation models and is dynamically adaptable to new ones. The paper further focuses on the facilities offered by the system for component classification, an important documentation technique which has also been proposed for retrieving reusable software. It is demonstrated that the inherently delicate and complex process of classification is streamlined and considerably facilitated by integrating it in a wider documentation environment and, especially, by connecting it with software static analysis. The benefits in terms of precision, consistency and ease of use can be significant for ...

L oosely coupled distributed systems are characterised by a separation of resources and a consequent need for a facility to aid in the location of those resources. Traditionally, this role of resource location has been fulfilled by a name service i.e. a facility which maps the name of a resource to its location at a given network address. As the size of the resource name space grows, however, additional support for resource location is required, in the form of support for the discovery of the name of the resource that is to be located. A trading facility implements an approach to resource location which eliminates the need to know the name of a resource in order to locate it and instead allows specification of a required service in an abstract manner. Resources (or services) are classified by type, and the location of such services is guided principally by a specification of the required service type, with requests for services being mapped directly to services of an appropriate type...

A key challenge in Component-Based Software Engineering (CBSE) is finding appropriate software components for reuse. A component broker that allows component vendors to make available their modules, and also allows component integrators to search and select components matching their requirements will help solve this problem. In this paper, we describe an E-Exchange for buying and selling of software components over the World Wide Web. The ComponentXchange uses an XML based specification language for components, which is a semi-formal specification language that can describe a rich and an extensible set of component properties including functional properties, non-functional attributes and licensing aspects. ComponentXchange supports two models of component trading. A component can be used either by downloading it and integrating it into the client application or by accessing it remotely over the network. It has a licensing server that enforces the licensing terms and conditions. ComponentXchange can be easily extended to support different payment models like pay-per-use, pay-per-user, etc.

A key challenge in Component-Based Software Engineering (CBSE) approaches to build software systems using pre-existing software components is searching and selecting appropriate software components for reuse. A component broker that allows component vendors to make available their modules, and allows component integrators to search and select components matching its requirements will provide a solution to this problem. In the present thesis, we present the design and architecture of ComponentXchange, an E-Exchange for buying and selling of software components over the World Wide Web.