A note on clique-width and tree-width for structures
نویسندگان
چکیده
We give a simple proof that the straightforward generalisation of clique-width to arbitrary structures can be unbounded on structures of bounded tree-width. This can be corrected by allowing fusion of elements.
منابع مشابه
Polynomial-time Algorithm for Isomorphism of Graphs with Clique-width at most 3
The clique-width is a measure of complexity of decomposing graphs into certain tree-like structures. The class of graphs with bounded clique-width contains bounded tree-width graphs. While there are many results on the graph isomorphism problem for bounded treewidth graphs, very little is known about isomorphism of bounded cliquewidth graphs. We give the first polynomial-time graph isomorphism ...
متن کاملChordal bipartite graphs of bounded tree- and clique-width
A bipartite graph is chordal bipartite if every cycle of length at least six has a chord. In the class of chordal bipartite graphs the tree-width and the clique-width are unbounded. Our main results are that chordal bipartite graphs of bounded vertex degree have bounded tree-width and that k-fork-free chordal bipartite graphs have bounded clique-width, where a k-fork is the graph arising from a...
متن کاملContainment of Monadic Datalog Programs via Bounded Clique-Width
Containment of monadic datalog programs over data trees (labelled trees with an equivalence relation) is undecidable. Recently, decidability was shown for two incomparable fragments: downward programs, which never move up from visited tree nodes, and linear childonly programs, which have at most one intensional predicate per rule and do not use descendant relation. As di erent as the fragments ...
متن کاملA characterisation of clique-width through nested partitions
Clique-width of graphs is defined algebraically through operations on graphs with vertex labels. We characterise the clique-width in a combinatorial way by means of partitions of the vertex set, using trees of nested partitions where partitions are ordered bottom-up by refinement. We show that the correspondences in both directions, between combinatorial partition trees and algebraic terms, pre...
متن کاملHypergraphs in Model Checking: Acyclicity and Hypertree-Width versus Clique-Width
The principal aim of model checking is to provide efficient decision procedures for the evaluation of certain logical formulae over finite relational structures. Graphs and hypergraphs are important examples of such structures. If no restrictions are imposed on the logical formulae and on the structures under consideration, then this problem of model checking has a very high computational compl...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- CoRR
دوره abs/0806.0103 شماره
صفحات -
تاریخ انتشار 2008