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Conjunctive Queries over Trees
[article]
2006
arXiv
pre-print
We study the complexity and expressive power of conjunctive queries over unranked labeled trees represented using a variety of structure relations such as "child", "descendant", and "following" as well as unary relations for node labels. We establish a framework for characterizing structures representing trees for which conjunctive queries can be evaluated efficiently. Then we completely chart the tractability frontier of the problem and establish a dichotomy theorem for our axis relations,
arXiv:cs/0602004v1
fatcat:7e2tycnqgncqpgfwrlyf4u7cve