Interoperability is a property referring to the ability of diverse systems to work together (inter-operate). The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to system performance.

Definition

The IEEE defines interoperability as:

the ability of two or more systems or components to exchange information and to use the information that has been exchanged.

Communication networks

In communication networks, the term can be defined as:

The ability of systems, units, or forces to provide services to and accept services from other systems, units or forces and to use the services exchanged to enable them to operate effectively together.
The condition achieved among communications-electronics systems or items of communications-electronics equipment when information or services can be exchanged directly and satisfactorily between them and/or their users. The degree of interoperability should be defined when referring to specific cases.
Source: from Federal Standard 1037C and from the Department of Defense Dictionary of Military and Associated Terms in support of MIL-STD-188.

In two-way radio, interoperability is composed of three dimensions:

compatible communications paths (compatible frequencies, equipment and signaling),
radio system coverage or adequate signal strength, and;
scalable capacity.

Software

With respect to software, the term interoperability is used to describe the capability of different programs to exchange data via a common set of exchange formats, to read and write the same file formats, and to use the same protocols. (The ability to execute the same binary code on different processor platforms is 'not' contemplated by the definition of interoperability.) The lack of interoperability can be a consequence of a lack of attention to standardization during the design of a program. Indeed, interoperability is not taken for granted in the non-standards-based portion of the computing world.

According to ISO/IEC 2382-01, Information Technology Vocabulary, Fundamental Terms, interoperability is defined as follows: "The capability to communicate, execute programs, or transfer data among various functional units in a manner that requires the user to have little or no knowledge of the unique characteristics of those units". [1]

Note that the definition is somewhat ambiguous because the user of a program can be another program and, if the latter is a portion of the set of program that is required to be interoperable, it might well be that it does need to have knowledge of the characteristics of other units. This definition focuses on the technical side of interoperability, while it has also been pointed out that interoperability is often more of an organizational issue: often interoperability has a significant impact on the organizations concerned, raising issues of ownership (do people want to share their data?), labor relations (are people prepared to undergo training?) and usability. In this context, a more apt definition is captured in the term "business process interoperability".

Interoperability can have important economic consequences, such as network externalities. If competitors' products are not interoperable (due to causes such as patents, trade secrets or coordination failures), the result may well be monopoly or market failure. For this reason, it may be prudent for user communities or governments to take steps to encourage interoperability in various situations. In the United Kingdom, for example, there is an eGovernment-based interoperability initiative called e-GIF. As far as user communities, Neutral Third Party is creating standards for business process interoperability. Another example of a neutral party is the RFC documents from the Internet Engineering Task Force (IETF).