This paper presents the SYDOX/MATCOMP/Xi project, funded by the French Ministry of Industry. The goal of the project was to provide the construction professionals with an on-line aid for component specification and selection at different levels of the construction life cycle. This two years project started in 1997 and involved several partners. This paper describes the main features of the information system: databases, query and communication systems. SYDOX(SYstème de DOnnées compleXes) is aimed at defining and demonstrating a prototype to access information about MATerials and COMPonents used in construction, implemented on a WWW server. Though the objective is general, the work was focused on a restricted sub-section of the construction domain. We describe the domain and the scope of the project, the starting point and the lessons learnt from the development of the prototype. We also propose some important ideas on which this research is based.