is an event-based concurrent, objectoriented language speci cally designed for prototyping system architectures. Two principle design goals are 1 to provide constructs for de ning executable prototypes of architectures, and 2 to adopt an execution model in which t h e concurrency, synchronization, data ow, and timing properties of a prototype are explicitly represented. This paper describes the partially ordered event set poset execution model and outlines with examples some of the event-based features for de ning communication architectures and relationships between architectures. Various features of Rapide are illustrated by excerpts from a prototype of the X Open distributed transaction processing reference architecture. Keywords| Rapide, architecture de nition languages, partially ordered event sets, architecture, prototyping, concurrency, simulation, formal constraints, constraint-based speci cation, event patterns, causality.

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Multiparadigm approach integrates programming language paradigms. We have proposed Holoparadigm (Holo) as a multiparadigm model oriented to development of distributed systems. Holo uses a logic blackboard (called history) to implement a coordination mechanism. The programs are organized in levels using abstract entities called beings. First, we describe the principal concepts of the Holoparadigm. After, we propose the Distributed Holo (DHolo), a model to support the distributed execution of programs developed in Holo. DHolo is based on object mobility and blackboards. This distributed model can be fully implemented on Java platform. Experiments were done using Voyager and Horb to implement mobility. Blackboards were implemented using Jada and JavaSpaces.

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In early 1999, VA Software launched a project to understand how the Internet development community had been able to produce software such as Linux, Apache and Samba that was generally developed faster and with higher quality than comparable commercially available alternatives [1,2,3,20]. Our goal was simple: determine how to make more software development projects successful.We discovered that successful Internet community projects employed a number of practices that were not well characterized by traditional software engineering methodologies. We now refer to those practices as Collaborative Software Development or CSD. Late in 1999 we developed the SourceForge platform to make it easy for even small software development projects to employ those practices, and in November of 1999 launched the SourceForge.net web site based on the SourceForge platform.The site was an overwhelming success, and in less than two years, grew to support more than 27,000 software development projects and over a quarter million software developers worldwide. SourceForge.net affords us an unequaled test bed for understanding CSD. In response to demand from companies seeking to enable CSD within their organizations, we announced a commercial version of the SourceForge platform, SourceForge Enterprise Edition, in August 2001. This paper describes the principles of CSD, the software development pain points those principles address, and our experience enabling CSD with the SourceForge platform.