Component composition has been over a decade a concept that supplements classical reference-based programming, but does not replace it to a larger extent. Though a new generation of component languages like ArchJava has pushed forwards composition from subcomponents, these languages fall back into class-based programming of methods when Java program code is to be written e.g. as a filter among subcomponents. To allow for a seamless composition process, we have developed the component language CompJava that introduces component fragments and plugs as means for composing a component both from subcomponents and structured units of code. In parallel, we have extended UML 2 component diagrams by the newly introduced concepts. This allows visualizing the compositional structure of components in order to better understand and communicate it. A graphical editor, called CompJava Designer, allows constructing relatively complex and distributed component systems by a seamless visual composition process.

Web services have many important advantages. But their great drawback, the invocation overhead, has not been a research focus. So far, only invocations of simple Web services were considered. But Web service composition may create additional performance problems. Our measurements demonstrate that Web service composition may reduce the maximal load of a system drastically. The reduction quotient increases quasi-exponentially with the number of service compositions. We call that phenomenon "service congestion" since it is not due to the combined payload of the composed services. Such detrimental performance effects can not be tolerated in many areas. For that reason, we propose an optimized service composition architecture as a solution. This service component architecture uses service connectors on top of standard Web service middleware. It optimizes automatically the local invocation of services with a Lookup&Service bus. The result is that no service congestion occurs since local service invocations have the cost of local calls

The class and interaction structure of object-oriented designs may become fairly complex, and consequently difficult to develop and understand.Design patterns allow to govern this complexity.This paper presents the design process of a domain-specific black-box framework for the control of automated manufacturing systems.The design is performed as a sequence of transformation steps, guided by the use of generative design patterns.Starting out from a domain-specific model.which does not provide a degree of reusability sufficiently high for a framework.the transformation steps increase the reusability until a satisfactory degree is reached.The resulting class and interaction structure allows to create each application of the considered manufacturing subdomain by selecting, configuring and parameterizing of the framework classes.

The relational model for data base organization introduced clearly defined basic algebraic concepts whose properties are well understood. As a consequence, questions of a semantic nature arise. Due to the mathematical nature of the relational model, these questions cannot be answered completely by it. Therefore, a data model is discussed that takes into account basic semantic properties that object types and relationships among them apparently have in the real world. The model permits a data base to be partitioned into independent object types which are natural insertion and deletion units, and associations among them. Independent object types are described by characteristics which are meaningful modification units.This data model permits us to analyze the ideas behind the relational theory more precisely, in particular the meaning of functional dependency and normalization. Insertion-deletion rules for relations in third normal form are developed, and proposals are made to avoid some drawbacks that exist even when relations in third normal form are used as the user interface to a data base.

Most of the literature on implementation of relations has been directed toward user features, with little attention paid to an overall conceptual view of underlying structures. Performance oriented considerations have been treated only for isolated problems.