With the growing advances in computing and communications technologies, the concept of system-of-systems (SoS) becomes widely recognized as it offers potential benefits and new challenges. Relevant perspectives related to SoS constitutes nowadays an active domain of research, among them those issues concerning the need of full interoperation. When it is related to enterprise information systems, the SoS paradigm may then be derived to a form of System-of-Information Systems (SoIS). This paper presents an overview of the features of the interoperation in SoIS and proposes guidelines to evaluate and formalize it in order to identify semantic gaps between information systems concepts and models. It provides, through an example, an approach to use Description Logic for evaluating semantic interoperability concerns.