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Fig. 9.10 Gram Data Model: The schema (on the
left
) and the instances (on the
right
)
Fig. 9.11 Gram query to find
students and their supervisors
Fig. 9.12 G-Log Data Model: The schema (on the
left
) and the instances (on the
right
)
whose language contains only alternating sequences of node and edge types,
starting and ending with a node type. The query language is based on hyperwalk
algebra with operations closed under the set of hyperwalks.
This hyperwalk facilitates the query of paths and the finding of adjacent node
and edge. A Gram query example is presented in Fig.
9.11
.
G-Log
G-Log [
24
] is a declarative, nondeterministic complete language for complex
objects with identity.
The data model of G-Log is (right down to minor details) the same as that of
GOOD (Fig.
9.12
). The main difference between G-Log and GOOD is that the
former is a declarative language, and that the latter is imperative. In G-Log, the basic
entity of a program is a rule. Rules in G-Log are graph-based and are built up from
colored patterns. A G-Log program is defined as a sequence of sets of G-Log rules.
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