Databases Reference
In-Depth Information
Figure 9: The path approach.
In Shanmugasundaram's method, the binary approach and the universal table
approach, database schema is dependent on the logical structure of XML
documents. Hence, in these methods, update of XML documents or insertion of
new XML documents may cause re-design of database schema.
Path expressions often appear in XML queries. In the path approach, paths are
stored as character string, hence, processing of path expressions can be made by
string comparison in SQL. However, other methods requires join operations in
proportion to the length of path expressions.
5
Indices for XML Documents
Indices for XML documents should have a data structure which is suitable for fast
access to document fragments based on document logical structures and/or
character strings.
According to Sacks-Davis
14)
, indexing of structured documents can be classified
into the following two approaches:
•
position-based indexing, and
