A signature tree is an index structure, in which each path represents a signature identifier for the signature pointed to by the corresponding leaf node.
Published in Chapter:
An Overview on Signature File Techniques
Yangjun Chen (University of Winnipeg, Canada)
Copyright: © 2009
|Pages: 11
DOI: 10.4018/978-1-60566-242-8.ch069
Abstract
An important question in information retrieval is how to create a database index which can be searched efficiently for the data one seeks. Today, one or more of the following four techniques have been frequently used: full text searching, B-trees, inversion and the signature file. Full text searching imposes no space overhead, but requires long response time. In contrast, B-trees, inversion and the signature file work quickly, but need a large intermediary representation structure (index), which provides direct links to relevant data. In this paper, we concentrate on the techniques of signature files and discuss different construction approaches of a signature file. The signature technique cannot only be used in document databases, but also in relational and object-oriented databases. In a document database, a set of semistructured (XML) documents is stored and the queries related to keywords are frequently evaluated. To speed up the evaluation of such queries, we can construct signatures for words and superimpose them to establish signatures for document blocks, which can be used to cut off non-relevant documents as early as possible when evaluating a query. Especially, such a method can be extended to handle the socalled containment queries, for which not only the key words, but also the hierarchical structure of a document has to be considered. We can also handle queries issued to a relational or an objectoriented database using the signature technique by establishing signatures for attribute values, tuples, as well as tables and classes.