Today, more than ever before, the primary challenge of conducting joint operations is increasingly summed up in one word: interoperability. The Joint Task Force (JTF) that fights the next conflict, small or large, does not exist until the need arises. Its approach to information management and the set of electronic information systems will be based in large part on which Service is in charge of the operation. Though all Services provide their essential sets of automated "tools," the particulars of which ones, how many, where they are located, etc., are all dependent on the situation and the decisions of the assigned Service Commander.

Determining how various systems are pulled together to accomplish a joint mission is one of the major challenges facing information systems architecture developers throughout the Department of Defense (DoD). Information systems built to meet specific Service requirements must still provide for the appropriate level of C4ISR interoperability to meet joint requirements. As such, understanding the specific nature and degree of interoperability required is a key consideration that must be accounted for when designing, constructing, and deploying any information technology architecture.

The Levels of Information Systems Interoperability (LISI) Reference Model presents a logical structure and a discipline or "maturity model" for improving interoperability incrementally between information systems. As such, LISI strengthens the ability to effectively manage information systems in context with mission effectiveness. It complements other activities that support improved use of information technology in the DoD mission, such as the Defense Information Infrastructure (DII) Master Plan, the DII Common Operating Environment (COE), the DoD Technical Reference Model (TRM), and Joint Technical Architecture (JTA).

The LISI Reference Model (LRM):

• Facilitates a common understanding of interoperability and its enablers at each level of sophistication of system-to-system interaction.
• Translates interoperability levels into requisite capabilities (procedures, applications, infrastructure, data) that form the basis for making comparisons between heterogeneous systems and for determining the degree to which system implementations conform to current DoD technical criteria.
• Builds on current DoD prescriptions to provide a methodology, maturity model, and process for assessing and improving interoperability incrementally in context with requirements analysis, systems development, acquisition, and fielding, and technology insertion.
• Provides the interoperability assessment "contribution" to the information technology "measure of performance (MOP)" called for in the ITMRA and other recent government legislation

Section 2 presents a brief overview of the LISI Reference Model. Section 3 discusses the relationships between LISI and operational, systems, and technical architecture views.