172 research outputs found
Automatic generation of simplified weakest preconditions for integrity constraint verification
Given a constraint assumed to hold on a database and an update to
be performed on , we address the following question: will still hold
after is performed? When is a relational database, we define a
confluent terminating rewriting system which, starting from and ,
automatically derives a simplified weakest precondition such that,
whenever satisfies , then the updated database will satisfy
, and moreover is simplified in the sense that its computation
depends only upon the instances of that may be modified by the update. We
then extend the definition of a simplified to the case of deductive
databases; we prove it using fixpoint induction
On relating CTL to Datalog
CTL is the dominant temporal specification language in practice mainly due to
the fact that it admits model checking in linear time. Logic programming and
the database query language Datalog are often used as an implementation
platform for logic languages. In this paper we present the exact relation
between CTL and Datalog and moreover we build on this relation and known
efficient algorithms for CTL to obtain efficient algorithms for fragments of
stratified Datalog. The contributions of this paper are: a) We embed CTL into
STD which is a proper fragment of stratified Datalog. Moreover we show that STD
expresses exactly CTL -- we prove that by embedding STD into CTL. Both
embeddings are linear. b) CTL can also be embedded to fragments of Datalog
without negation. We define a fragment of Datalog with the successor build-in
predicate that we call TDS and we embed CTL into TDS in linear time. We build
on the above relations to answer open problems of stratified Datalog. We prove
that query evaluation is linear and that containment and satisfiability
problems are both decidable. The results presented in this paper are the first
for fragments of stratified Datalog that are more general than those containing
only unary EDBs.Comment: 34 pages, 1 figure (file .eps
Tree inclusions in windows and slices
is an embedded subtree of if can be obtained by deleting some nodes from : if a node is deleted, all edges adjacent to are also deleted, and outgoing edges are replaced by edges going from the parent of (if it exists) to the children of . Deciding whether is an embedded subtree of is known to be NP-complete. Given two trees (a target and a pattern ) and a natural number , we address two problems: 1. counting the number of windows of having height exactly and containing pattern as an embedded subtree, and 2. counting the number of slices of having height exactly and containing pattern as an embedded subtree
Complexity of Monadic inf-datalog. Application to temporal logic.
In [11] we defined Inf-Datalog and characterized the fragments of Monadic inf-Datalog that have the same expressive power as Modal Logic (resp. , alternation-free Modal -calculus and Modal -calculus). We study here the time and space complexity of evaluation of Monadic inf-Datalog programs on finite models. We deduce a new unified proof that model checking has 1. linear data and program complexities (both in time and space) for and alternation-free Modal -calculus, and 2. linear-space (data and program) complexities, linear-time program complexity and polynomial-time data complexity for (Modal -calculus with fixed alternation-depth at most ).
A unifying theorem for algebraic semantics and dynamic logics
AbstractA unified single proof is given which implies theorems in such diverse fields as continuous algebras of algebraic semantics, dynamic algebras of logics of programs, and program verification methods for total correctness. The proof concerns ultraproducts and diagonalization
An automata characterisation for multiple context-free languages
We introduce tree stack automata as a new class of automata with storage and
identify a restricted form of tree stack automata that recognises exactly the
multiple context-free languages.Comment: This is an extended version of a paper with the same title accepted
at the 20th International Conference on Developments in Language Theory (DLT
2016
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