The capture, the structuring and the exploitation of the expertise or the capabilities of an ``object'' (like a business partner, an employee, a software component, a Web site, etc.) are crucial problems in various applications, like cooperative and distributed applications or e-business and e-commerce applications. The work we describe in this paper concerns the advertising of the capabilities or the know-how of an object. The capabilities are structured and organized in order to be used when searching for objects that satisfy a given objective or that meet a given need. One of the originality of our proposal is in the nature of the answers the intended system can return. Indeed, the answers are not Yes/No answers but they may be cooperative answers in that sense that when no single object meets the search criteria, the system attempts to find out what a set of ``complementary'' objects do satisfy the whole search criteria, every object in the resulting set satisfying part of the criteria. n this approach, Description Logics (DL) is used as a knowledge representation formalism and classification techniques are used as search mechanisms. The determination of the “complementary objects” is founded on the DL complement concept.