Military Communications and Information Technology: A Trusted ...

Chapter 3: Information Technology for Interoperability and Decision...
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shall support, the systems are both based on the same part of reality. Following
the definition giving in the introduction, the models the systems are using are purposeful
abstractions and simplification of their perception of this common reality.
The resulting implementations should therefore be similar enough to be alignable by
designing a common technical infrastructure that supports mediation between
the different viewpoints. This view is also supported by the IEEE definition cited
earlier in this white paper: two systems can be made interoperable if we can mediate
the data used in both systems to each other to use them in the respective system.
In order to gain a better understanding of the theoretical underpinnings
of interoperation between two federate simulation systems the Levels of Conceptual
Interoperability Model (LCIM) was developed. This model and its layers allow
clearly distinguishing between the three governing concepts of interoperation:
• Integratability contends with the physical/technical realms of connections
between systems, which include hardware and firmware, protocols, networks,
etc.
• Interoperability contends with the software and implementation details of interoperations;
this includes exchange of data elements via interfaces, the use
of middleware, mapping to common information exchange models, etc.
• Composability contends with the alignment of issues on the modelling
level. The underlying models are purposeful abstractions of reality used
for the conceptualization being implemented by the resulting systems.
For meaningful interoperation of two systems, all three governing concepts
are necessary: we need compatible infrastructures, interoperable implementations,
and composable models. In particular the third concept of composability has been
neglected by interoperability standards so far. The LCIM defines several layers
of interoperation to address particular challenges. It can be used descriptively (what
has been accomplished) as well as prescriptively (what needs to be accomplished).
These levels are defined as follows:
• If systems are stand-alone applications with no interconnection, there
is obviously no interoperability.
• The technical layer deals with infrastructure and network challenges, enabling
systems to exchange carriers of information. This is the domain of integratability;
a communication protocol to exchange signals exists.
• The syntactic layer deals with challenges to interpret and structure the information
to form symbols within protocols. This layer belongs to the domain
of interoperability; common symbols – like the use of Unicode or ANSI
code – are identified.
• The semantic layer provides a common understanding of the information
exchange. On this level, the pieces of information that can be composed to
objects, messages, and other higher structures are identified. This level also
support interoperability: it introduces common terms to tag structures that
represent tags that are used to name functions, variables, and constants.