143 search results - page 11 / 29 » Query Order and the Polynomial Hierarchy |
CSL
2009
Springer
15 years 1 months ago
2009
Springer
We introduce tree-width for first order formulae , fotw(). We show that computing fotw is fixed-parameter tractable with parameter fotw. Moreover, we show that on classes of formul...
ICDT
2007
ACM
15 years 3 months ago
2007
ACM
Abstract. In many cases, users may want to consider incomplete answers to their queries. Often, however, there is an overwhelming number of such answers, even if subsumed answers a...
LICS
2002
IEEE
15 years 2 months ago
2002
IEEE
We study relations on trees defined by first-order constraints over a vocabulary that includes the tree extension relation Ì Ì ¼, holding if and only if every branch of Ì ex...
PODS
2010
ACM
15 years 2 months ago
2010
ACM
It is well known that a search engine can significantly benefit from an auxiliary database, which can suggest interpretations of the search query by means of the involved concep...
ESWS
2009
Springer
15 years 4 months ago
2009
Springer
We consider the problem of a user querying semistructured data such as RDF without knowing its structure. In these circumstances, it is helpful if the querying system can perform a...