Ability of different types of computers, networks, operating systems, and applications to work together effectively, without prior communication, in order to exchange information in a useful and meaningful manner. There are three aspects of interoperability: semantic, structural and syntactical.
Ability of two or more systems or components to exchange information and to use the information that has been exchanged
[IEEE Standard Computer Dictionary: A Compilation of IEEE Standard Computer Glossaries. New York: 1990], http://www.sei.cmu.edu/str/indexes/glossary/interoperability.html
[...] is the ability of a system or a product to work with other systems or products without special effort on the part of the customer. Interoperability becomes a quality of increasing importance for information technology products as the concept that "The network is the computer" becomes a reality. For this reason, the term is widely used in product marketing descriptions.
see also "Interoperability. What is it and Why should I want it?", author Paul Miller, 21-Jun-2000, Ariadne Issue 24,
Interoperability and European Research Framework Programms
These issues of interoperability are linked to the objectives of the research framework programm related to "Networked businesses" (in FP6) and "Enterprise Interoperability" (FP7); its focus is the development of technologies of information and communication supporting the organisational networking, process integration and resources sharing.