Information systems aim to be decentralized and to make use of different resources or business knowledge more and more externalized and used on demand. Today SOAs are presented as a possible answer to the implementation of these decentralized information systems, but require enterprises to major challenges : the exposure of their business functionality in the form of services, the use of these services, but also the use of services provided by third parties. The approach we propose under this article disclaims SOA vision in the context of a conceptual architecture for the information systems engineering, encompassing the definition of a business services repository and the composition of these services in the form of agile services orchestrations.