The unambiguous speci cation of the requirements of real-time software systems is a non-trivial task. In this report we describe some experiences in AE modeling, using a simple extension to VDM as notational vehicle.

We offer a new viewpoint on some of the generic structures constructed using Hrushovski’s predimensions and show that they are natural reducts of quite straightforward trivial, one-based stable structures. 2000 Mathematics Subject Classification: 03C45.

Given a quasi-special endomorphism ρ of a C∗ -algebra A with nontrivial center, we study an extension problem for automorphisms of A to a minimal cross-product B of A by ρ . Exploiting some aspects of the underlying generalized Doplicher-Roberts duality theory based on Pimsner algebras, an obstruction to the existence of such extensions is found and described in terms of sections of a suitable ...

We consider the symplectic Euler method for Hamiltonian systems with holonomic constraints and its generalization to a class of overdetermined differential-algebraic equations (ODAEs). It is shown that a natural extension of the symplectic Euler method as a SPARK method is inconsistent for ODAEs which are nonlinear in the algebraic variables. A different non-trivial extension is given and shown...

A recently proposed molecular model is discussed as a non-trivial extension of the Ising model. For d = 2 the two models are shown to be equivalent, while for d > 2 the molecular model describes a peculiar second order transition from an isotropic high temperature phase to a low-dimensional anisotropic low temperature state. The general mean field analysis is compared with the results achieved ...

Let $p:Xlo B$ be a locally trivial principal G-bundle and $wt{p}:wt{X}lo B$ be a locally trivial principal $wt{G}$-bundle. In this paper, by using the structure of principal bundles according to transition functions, we show that $wt{G}$ is a covering group of $G$ if and only if $wt{X}$ is a covering space of $X$. Then we conclude that a topological space $X$ with non-simply connected universal...

In this paper we introduce and explore an extension to the existing paradigm of model transformation. Specifically, we extend existing model transformation approaches by considering reference models and human input as important sources for and during model transformation. To cater for this new type of model transformation, we develop an approach grounded on a common generic model and a series o...

Let F be a differential field of characteristic zero with algebraically closed field of constants. We provide an explicit description of the twisted Lie algebras of PGL3-equivariant derivations on the coordinate rings of F -irreducible PGL3-torsors in terms of nine-dimensional central simple algebras over F . We use this to construct a Picard–Vessiot extension which is the function field of a n...

Default logic was introduced by Reiter in 1980. In 1992, Gottlob classified the complexity of the extension existence problem for propositional default logic as Σp2-complete, and the complexity of the credulous and skeptical reasoning problem as Σp2-complete, resp. Π p 2-complete. Additionally, he investigated restrictions on the default rules, i.e., semi-normal default rules. Selman used in 19...