Interoperability is a software property for exchanging and using information between software systems.Some interoperability proposals are intended to use metamodels, models, and frameworks, in which visual representations are included.However, such proposals describe interoperability according to their point of view, focus of analysis, solution techniques, and specific level of interoperability; in addition, some of the visual representations use no standards, which lead to subjective interpretations by the reader.In this paper we propose a representation formalizing interoperability which includes essential elements and structural relationships among them.After a review of previous work, a summary of the analyzed literature is performed by using linguistic analysis in order to recognize the relationships among interoperability essential elements and mapping them to controlled language expressions.Finally, the mapping process is used to represent the interoperability essential elements and their relationships by using pre-conceptual schemas linked to the definition of each essential element.As a result, a pre-conceptual schema of the software system interoperability is proposed.Such a pre-conceptual schema is also used for explaining an interoperability lab study adapted from the literature.The proposed pre-conceptual schema explains the interoperability between two software systems and allows for characterizing interoperability problems and solutions.