8. Remote definitions

Tutorial on SDL-88
Belina, Hogrefe (edits Reed)

Figure 34 illustrates the traditional syntax structure of a system description.

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Figure 34 Traditional syntax structure of a system description

This structuring is suitable from the tool point of view, but it poses the following problems for the human being:

	no overview,
	difficulty in mapping between documents and definitions (the relation between documents is different from the relation between definitions)

The solution to these problems is the remote definition construct in SDL A remote definition is a definition that has bee n removed from its defining context to gain overview. II is similar to a macro definition, but is "called" from exactly one place (the defining context) using a reference. See figure 35.

By using remote definitions, the two concrete representation forms: SDL/GR (graphical) and SDL/PR (textual) can be mixed at the discretion of the- user of SDL, as illustrated below:

<system definition> ::=
    {<textual system definition> | <system diagram>}
    (<remote definition>}*

<remote definition> ::=
    <definition> | <diagram>

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Figure 35 Remote definitions