Databases Reference
In-Depth Information
Figure 3: Graph Equations of XML
Two kinds of attributes correspond to XML's: we call them label attributes
(abbreviated by
l-attr
) and element attributes (abbreviated by
e-attr
), respectively.
This syntax follows
one
Yasukawa et al 90)
and the semantics is also defined
on hypersets
Aczel 88)
as in
. Consider the following system of graph equations:
If each of graphs does not have an identifier and any label attributes, they can be
reduced by giving
as follows:
As for graph isomorphism, we require additional rules.
Consider an example which means a person deelpy in love with each other::
This is a circular one. In our extended XML, it is written as follows:
