Military Communications and Information Technology: A Trusted ...

212 Military Communications and Information Technology...
Multinational character of military units and operations as well as C2 systems
integration challenges leads us to the idea of DSLs with multilingual support. With
multilingual support we mean DSLs with different syntax, but with mutually related
semantic processing [11], [12]: At first sight, a language used e.g. in a U.S. system
would seem to be different than that in a Slovak system, but the tasks that can be
described by language constructions in both systems would probably be very similar.
Similarly, in the case of C2 system integration an XML-based language would
be preferred (as in the case of [10]). On the other hand, analogically as the great
majority of programming languages is not XML-based, when the primary target
of the language is a human, an XML-based language probably would not be
the preferred choice.
Now let us look at the syntactical and semantic aspects of CLs, bearing in mind
multilingual character of DSLs.
II. Syntax, semantics, and processing of computer languages
In order to be able to be processed by machines CLs need to have exactly
and unambiguously specified their syntax and semantics. Syntax of CLs is usually
specified by means of context-free grammars (CFGs) or from CFGs derived
Backus-Naur forms (BNFs) [2], [13], [14], [15].
A context-free grammar is a 4-tuple
G = (N, T, P, S), (1)
where N is a finite set of non-terminal characters (or variables), T is a finite set
of terminal characters (or terminals), S, SÎN is the starting symbol of the grammar
from which each derivation starts, and P is a finite set of productions (or rewriting
rules) of the form
B → α, (2)
where BÎN is the left-hand side and αÎ(NÈT) * is the right-hand side of the production.
When designing a DSL with multilingual support, it seems to be rational to
separate its abstract syntax from its concrete syntaxes. For example, if we need two
language representations, we will use a common abstract syntax and two concrete
syntaxes. Both abstract and concrete syntaxes can be expressed using CFGs (1) and
in both cases syntax of individual productions has to be designed with respect to
semantic processing of the productions.
The grammar expressing abstract syntax is not intended to be directly used
by the parser, therefore it does not have to be unambiguous nor deterministic
context-free of a specified type. It should define elements, or concepts, that make
up a language (regardless of the concrete form of the language) and the rules for
composition of these elements [12]. When designing an abstract syntax of a lan-