Introduction to Architecture Session Marseilles September 1999 John Harvey CERN / LHCb

Importance of Software Architecture Booch : “Development of complex software systems should be architecture-driven” Architecture specifications provide a blueprint for everyone to follow facilitate communication between developers developers know how to contribute their pieces Architectures can be designed to accommodate new requirements or changes in technology adaptable - more resilient to change flexible and extensible - they must evolve in an incremental fashion Implemented via frameworks that can be reused for different data processing applications ensure architecture is respected solve standard computing tasks once….must do a lot and be configurable provide clean interface for end user - must be easy to understand and use

Goals of Architecture Session Raise awareness of the importance of firstly specifying the software architecture before building large software systems Introduce the vocabulary explaining the meaning of commonly used terms Introduce through examples common architectural patterns (styles) Illustrate the important architectural features that have impact on quality Introduce through examples architectures in use in HEP today Illustrate the scope of the architecture conceptual view illustrating logical structure concrete view illustrating the physical structure (packaging, building releases, impact on performance…) Exchange opinions on what constitutes a good architecture as our data processing needs are so similar a good architecture for one experiment should be applicable elsewhere Identify important issues that need to be addressed and concrete actions that should be taken

The goals of the session are not to….. Solve technical issues Choose the best technical solution Scope does not cover very specific application domains such as the data acquisition system

Architecture Study Group Setup end June 1999 as a technical forum to study the issue of software architecture .. .. and to help prepare for this workshop Membership : Alberto Aimar, John Apostolakis, Rene Brun, Dirk Duellmann, John Harvey, Vincenzo Innocente, Pere Mato, RD Schaffer, David Stickland, Lassi Tuura Christian Arnault, Federico Carminati, Fons Rademacker, Craig Tull, Pierre vande Vyvre Met seven times during the summer - informal Results of deliberations kept on a web site copies of slides and bibliography of relevant published material and web sites URL : http://lhcb.cern.ch/computing/SWarchWG/html/Default.htm Interest to continue after the workshop come back to in the discussion