The run-time component??”the generic modeling tool itself.
The metamodeling language was ER extended with some constraints and the
ability to have attributes whose values were derived from other attributes. It allowed
triggers on events applying to attributes and relationships.TBK de?¬?nitions were in the
form of textual ?¬?les in four languages:
. Data de?¬?nition language (DDL), which speci?¬?ed the basic objects and the
attributes they had,
. Graph description language (GDL), which speci?¬?ed the graphical symbols, but
also simple relationship and decomposition rules,
. Format description language (FDL), a low-level description of the individual
windows, buttons, menus, and so on that make up the user interface;
. Text layout language (LL), describing a structured text format of user-enterable
text ?¬?elds interspersed with ?¬?xed text and punctuation.
A BRIEF HISTORY OF TOOLS 363
DDL and GDL appear not dissimilar to the corresponding parts in MetaEdit??™s
textual metamodels, although with a rather more involved syntax. The LL text layout
language appears a useful addition, although little is mentioned about it in the
documentation and articles. The need to specify tool behavior in FDL, however,
seems to be a symptom of the level of abstraction being closer to that of a framework
than a true metaCASE tool: it should be possible to provide a good generic interface,
or generate one based solely on the DDL and GDL input.
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