Logics for n-ary queries in trees.
In computer science many data are
shaped as trees. In the context of the Web, it is the case
for XML formatted data in particular. XML is a markup language
that has rapidly become a standard for information storage and
data exchange.
As query languages for relational databases are not well-suited to XML
data, the need to have query languages specific to XML
documents has increased. We distinguish unary queries which select
a set of subparts of a document from n-ary queries which
select a set of n-tuples of subparts of a document. Many logical
formalisms for unary queries have been proposed, but less work has
been done on logical formalisms for n-ary queries.
This thesis is a fundamental study of n-ary queries
that proposes two logical formalisms for n-ary queries:
an extension of the navigational paradigm of the W3C standard
XPath to n-ary queries, called the composition language,
and an adapation of the spatial logic TQL introduced
by Cardelli and Ghelli.
The question of expressive power, the complexity of the query evaluation problem
as well as the satisfiability problem are considered. In particular,
the satisfiability problem for a TQL fragment is proved to be
decidable by reduction to the emptiness test of a new class of
tree automata with global constraints that is studied independently.
Thesis manuscript
Defense slides
TEL repository