Tree pattern query minimization
The VLDB Journal — The International Journal on Very Large Data Bases
Containment and equivalence for a fragment of XPath
Journal of the ACM (JACM)
Efficient algorithms for processing XPath queries
ACM Transactions on Database Systems (TODS)
Semantic characterizations of navigational XPath
ACM SIGMOD Record
Structural properties of XPath fragments
Theoretical Computer Science - Database theory
Processing queries on tree-structured data efficiently
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Structural characterizations of the semantics of XPath as navigation tool on a document
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Efficient algorithms for the tree homeomorphism problem
DBPL'07 Proceedings of the 11th international conference on Database programming languages
A methodology for coupling fragments of XPath with structural indexes for XML documents
DBPL'07 Proceedings of the 11th international conference on Database programming languages
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We study the expressiveness of a positive fragment of path queries, denoted Path$\mathstrut^+$, on node-labeled trees documents. The expressiveness of Path$\mathstrut^+$ is studied from two angles. First, we establish that Path$\mathstrut^+$ is equivalent in expressive power to a particular sub-fragment as well as to the class of tree queries, a sub-class of the first-order conjunctive queries defined over label, parent-child, and child-parent predicates. The translation algorithm from tree queries to Path$\mathstrut^+$ yields a normal form for Path$\mathstrut^+$ queries. Using this normal form, we can decompose a Path$\mathstrut^+$ query into sub-queries that can be expressed in a very small sub-fragment of Path$\mathstrut^+$ for which efficient evaluation strategies are available. Second, we characterize the expressiveness of Path$\mathstrut^+$ in terms of its ability to resolve nodes in a document. This result is used to show that each tree query can be translated to a unique, equivalent, and minimal tree query. The combination of these results yields an effective strategy to evaluate a large class of path queries on documents.