In Figure 7 a basic constraint is reported. In particular this constraint imposes that
the time interval of an edge between a complex node and a simple node must be
related to the time interval of the complex node. Intuitively, the relation between a
complex node and a simple node cannot survive the complex node; thus, the time
interval of the edge cannot start before and cannot end after the valid time of the
complex node, as depicted in Figure 7. This is due to the fact that we suppose that a
complex node is related to its properties (simple nodes) while it is valid. The edgerelated
time interval [tjs,tje] starts after and ends before the time interval [ths,the] of
the complex node.
Figure 7(a) identifies the subgraphs where the constraint has to be applied, and the
set of formulae representing restrictions imposed on those subgraphs. Figure 7(b)
shows an example of intervals satisfying the related constraint.
Figure 8 shows a domain-dependent constraint on the relation between a product
and its categories. In particular this constraint imposes that a product must be related
to a category; that is, a product can be inserted in the catalogue only if it is
connected to at least one category.
Figure 8(a) identifies the subgraphs where the constraint has to be applied, and the
formula representing restrictions imposed on those subgraphs.
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