Up to a recent time, numbers of projects did not make available to the whole community the data resulting from the spatial or terrestrial missions. Since the advent of new technologies, the interoperability between the data and service providers has become a priority because it allows an easy access and sharing of various data (catalogues, images, spectrum ...) and it leads to the concept of Virtual Observatory. The astronomer will in a near future have new “virtual” instruments useful for his research through simple Web interfaces or user friendly tools. Collaborations are essential in order to lead to the consensuses and the bases necessary for its construction. National (OV France, U.S. NVO...) and transnational (ESA, ESO) projects have joined together within the International Virtual Observatory Alliance to take part in the development of Recommendations in various fields (Data Model, Data Access Layer, Semantics, Grid, etc.) through biannual dedicated conferences.