Querying structured hyperdocuments

We present a document model which integrates the logical structure and hypertext link structure of hyperdocuments in order to manage structured documents with hypertext links. Based on this model we define a new structure query language which expresses the structure query using path expressions. To process a structure query in a document management system which represents structure information as database relations, costly join operations are used to find a relationship between elements in a document hierarchy. In order to overcome this problem, schemes based on the parse tree and element locator have been used (Blake, 1994). We propose a new structure query processing scheme that uses unique element identifiers (UIDs) to evaluate structure queries. Our scheme has advantages over previous schemes since it can obtain the UIDs of the ancestors and descendents directly from the UID of a node without disk access. We present relational database schemes for our scheme as well as others and compare the query processing costs. In order to support direct access to a document element, keyword indices to it should be provided. We propose three kinds of inverted index structures for efficient structure query processing