For example, the
home page of a WWW site can be represented by means of an entry point. Graph
edges can indicate both logical and navigational relationships. A logical edge has a
label indicating the relationship name.
The eXtensible Markup Language (XML) (World Wide Web Consortium, 1998)
is spreading out as a standard for representing, exchanging, and publishing semistructured
information by means of a simple and flexible text format derived from
the Standard Generalized Markup Language (World Wide Web Consortium, 1995).
Temporal Semistructured Data Models and Data Warehouses 28
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XML is a markup language designed to describe data by means of a set of tags,
which are not predefined. XML allows the author of the document to define the
author??™s own tags and document structure.
XML documents can be easily represented as trees or graphs. For example the XPath
Data Model (World Wide Web Consortium, 2005a) allows the representation of an
XML document as a tree. XPath uses path expressions to address the nodes in the
XML trees.
Temporal.Semistructured.Data
As in the classical context, also in the context of semistructured data it is interesting
to take into account the dynamic aspects of data to represent their evolutions
through time and eventually through consecutive updates.
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