This thesis studies CSPs where the variables can take values from an infinite domain, and studies the limits of complexity classification, and presents classes of computational problems provably do not exhibit a complexity dichotomy into hard and easy problems.Expand

It is shown that the number of edges in random series-parallel graphs is asymptotically normal with linear mean and variance, and that it is sharply concentrated around its expected value.Expand

An expected polynomial time algorithm is presented to generate a labeled planar graph uniformly at random and recurrence formulas that count all such graphs with n vertices and m edges are derived, based on a decomposition into 1-, 2-, and 3- connected components.Expand

This work presents a complete complexity classification of the constraint satisfaction problem (CSP) for temporal constraint languages: if the constraint language is contained in one out of nine temporal constraint language, then the CSP can be solved in polynomial time; otherwise, the C SP is NP-complete.Expand

Surjective homomorphism problems seem to be harder to classify and this work examines especially three concrete problems that have arisen from the literature, two of whose complexity remains open.Expand

This paper investigates drawings (totally ordered forests) as models of syntactic structure. It oers a new model-based perspective on lexicalised Tree Adjoining Grammar by characterising a class of… Expand

Omega-categoricity is a rather strong model-theoretic assumption on a relational structure, and it can be used to show that many techniques for constraint satisfaction with finite templates extend to omega- categorical templates.Expand

This work applies the universal-algebraic approach to infinite-valued constraint satisfaction, and shows that an equality constraint language is tractable if it admits a constant unary polymorphism or an injective binary polymorphism, and is NP-complete otherwise.Expand

Function clones are sets of functions on a fixed domain that are closed under composition and contain the projections. They carry a natural algebraic structure, provided by the laws of composition… Expand

It is proved that the primitive positive definable relations over an ω-categorical structure Γ are precisely the relations that are preserved by the polymorphisms of Γ.Expand