
Next Generation Information Technologies and Systems
Author(s) -
Alon Halevy,
Avigdor Gal
Publication year - 2002
Publication title -
lecture notes in computer science
Language(s) - English
Resource type - Book series
SCImago Journal Rank - 0.249
H-Index - 400
eISSN - 1611-3349
pISSN - 0302-9743
DOI - 10.1007/3-540-45431-4
Subject(s) - computer science , information system , engineering , electrical engineering
This paper discusses evaluation of select-project (SP) queries over an XML document. A SP query consists of two parts: (1) a conjunction of conditions on values of labels (called the selection) and (2) a series of labels whose values should be outputed (called the projection). Query evaluation involves finding tuples of nodes that have the labels mentioned in the query and are related to one another other in a meaningful fashion. Several different semantics for query evaluation are given in this paper. Some of these semantics also take into account the possible presence of incomplete information. The complexity of query evaluation is analyzed and evaluation algorithms are described.
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