1. A few definitions to set the scene

Software reuse is defined by models, architectures and styles.

• A pattern is defined by Martin Fowler as "an idea that has been useful in a particular context and is likely to be useful in other contexts".

  This notion of model is valid at all levels, from the piece of code that solves a particular problem to a group of functions in a vast domain such as telecommunications or accounting.

• The software architecture of a program or system is the description of its structure, which groups together software components, connectors (external properties of these components) and the relationships between components and connectors.

• An architecture style defines a family of systems in terms of structural models, a vocabulary of components and connectors, and rules or constraints...