Integrating information by outerjoins and full disjunctions (extended abstract)
PODS '96 Proceedings of the fifteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Queries with incomplete answers over semistructured data
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
On the foundations of the universal relation model
ACM Transactions on Database Systems (TODS)
A simplied universal relation assumption and its properties
ACM Transactions on Database Systems (TODS)
Representing and querying XML with incomplete information
PODS '01 Proceedings of the twentieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Principles of Database and Knowledge-Base Systems: Volume II: The New Technologies
Principles of Database and Knowledge-Base Systems: Volume II: The New Technologies
Can we use the universal instance assumption without using nulls?
SIGMOD '81 Proceedings of the 1981 ACM SIGMOD international conference on Management of data
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
ICDT '97 Proceedings of the 6th International Conference on Database Theory
Combining the Power of Searching and Querying
CooplS '02 Proceedings of the 7th International Conference on Cooperative Information Systems
SQL4X: A Flexible Query Language for XML and Relational Databases
DBPL '01 Revised Papers from the 8th International Workshop on Database Programming Languages
Generating Relations from XML Documents
ICDT '03 Proceedings of the 9th International Conference on Database Theory
Efficiently enumerating results of keyword search over data graphs
Information Systems
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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.