Abstract
With the development of the web and the intense research for a semantic web, the need arises for standardized and rigorous semantic specification both of Services on the semantic web and of the objects and processes that these Services offer to a potential client. In this report, our focus is with Learning Services, i.e. Web Services whose purpose is to offer educational services to clients. Such services are the owners of Learning Objects, which they deliver for use to their clients. Though the need for standardizing learning objects has become apparent, there is no substantial contribution towards a reference architecture for Learning Objects. We introduce here the CROP architecture, based on the notions of Concept, Resource, Order and Product.