Linear Temporal Logic and Propositional Schemata, Back and Forth (extended version)

This paper relates the well-known Linear Temporal Logic with the logic of propositional schemata introduced by the authors. We prove that LTL is equivalent to a class of schemata in the sense that polynomial-time reductions exist from one logic to the other. Some consequences about complexity are given. We report about first experiments and the consequences about possible improvements in existing implementations are analyzed.Comment: Extended version of a paper submitted at TIME 2011: contains proofs, additional examples & figures, additional comparison between classical LTL/schemata algorithms up to the provided translations, and an example of how to do model checking with schemata; 36 pages, 8 figure

An Algebra of Hierarchical Graphs

We define an algebraic theory of hierarchical graphs, whose axioms characterise graph isomorphism: two terms are equated exactly when they represent the same graph. Our algebra can be understood as a high-level language for describing graphs with a node-sharing, embedding structure, and it is then well suited for defining graphical representations of software models where nesting and linking are key aspects

Virtual Easter Egg Hunting: A Thought-Experiment in Embodied

Abstract. The Novamente Cognition Engine (NCE) architecture for Artificial General Intelligence is briefly reviewed, with a focus on exploring how the various cognitive processes involved in the architecture are intended to cooperate in carrying out moderately complex tasks involving controlling an agent embodied in the AGI-Sim 3D simulation world. A handful of previous conference papers have reviewed the overall architecture of the NCE, and discussed some accomplishments of the current, as yet incomplete version of the system; this paper is more speculative and focuses on the intended behaviors of the NCE once the implementation of all its major cognitive processes is complete. The "iterated Easter Egg Hunt" scenario is introduced and used as a running example throughout, due to its combination of perceptual, physical-action, social and selfmodeling aspects. To aid in explaining the intended behavior of the NCE, a systematic typology of NCE cognitive processes is introduced. Cognitive processes are typologized as global, operational or focused; and, the focused processes are more specifically categorized as either forward-synthesis or backward-synthesis processes. The typical dynamics of focused cognition is then modeled as an ongoing oscillation between forward and backward synthesis processes, with critical emergent structures such as self and consciousness arising as attractors of this oscillatory dynamic. The emergence of models of self and others from this oscillatory dynamic is reviewed, along with other aspects of cognitive-process integration in the NCE, in the context of the iterated Easter Egg Hunt scenario

Ontology-Based Production Simulation with OntologySim

Imagine the possibility to save a simulation at any time, modify or analyze it, and restart again with exactly the same state. The conceptualization and its concrete manifestation in the implementation OntologySim is demonstrated in this paper. The presented approach of a fully ontology-based simulation can solve current challenges in modeling and simulation in production science. Due to the individualization and customization of products and the resulting increase in complexity of production, a need for flexibly adaptable simulations arises. This need is exemplified in the trend towards Digital Twins and Digital Shadows. Their application to production systems, against the background of an ever increasing speed of change in such systems, is arduous. Moreover, missing understandability and human interpretability of current approaches hinders successful, goal oriented applications. The OntologySim can help solving this challenge by providing the ability to generate truly cyber physical systems, both interlocked with reality and providing a simulation framework. In a nutshell, this paper presents a discrete-event-based open-source simulation using multi-agency and ontology

Web Information Systems: Usage, Content, and Functionally Modelling

The design of large-scale data-intensive web information systems (WIS) requires a clear picture of the intended users and their behaviour in using the system, a support of various access channels and the technology used with them, and an integration of traditional methods for the design of data-intensive information systems with new methods that address the challenges arising from the web-presentation and the open access. This paper presents the conceptual modelling parts of a methodology for the design of WISs that is based on an abstract abstraction layer model (ALM). It concentrates on the two most important layers in this model: a business layer and a conceptual layer. The major activities on the business layer deal with user profiling and storyboarding, which addresses the design of an underlying application story. The core of such a story can be expressed by a directed multi-graph, in which the vertices represent scenes and the edges actions by the users including navigation. This leads to story algebras which can then be used to personalise the WIS to the needs of a user with a particular profile. The major activities on the conceptual layer address the support of scenes by modelling media types, which combine links to databases via extended views with the generation of navigation structures, operations supporting the activities in the storyboard, hierarchical presentations, and adaptivity to users, end-devices and channels. Adding presentation style options this can be used to generate the web-pages that will be presented to the WIS users

Machine Assisted Proofs of Recursion Implementation

Three studies in the machine assisted proof of recursion implementation are described. The verification system used is Edinburgh LCF (Logic for Computable Functions). Proofs are generated, in LCF, in a goal-oriented fashion by the application of strategies reflecting informal proof plans. LCF is introduced in Chapter 1. We present three case studies in which proof strategies are developed and (except in the third) tested in LCF. Chapter 2 contains an account of the machine generated proofs of three program transformations (from recursive to iterative function schemata). Two of the examples are taken from Manna and Waldinger. In each case, the recursion is implemented by the introduction of a new data type, e.g., a stack or counter. Some progress is made towards the development of a general strategy for producing the equivalence proofs of recursive and iterative function schemata by machine. Chapter 3 is concerned with the machine generated proof of the correctness of a compiling algorithm. The formulation, borrowed from Russell, includes a simple imperative language with a while and conditional construct, and a low level language of labelled statements, including jumps. We have, in LCF, formalised his denotational descriptions of the two languages and performed a proof of the preservation of the semantics under compilation. In Chapter 4, we express and informally prove the correctness of a compiling algorithm for a language containing declarations and calls of recursive procedures. We present a low level language whose semantics model a standard activation stack implementation. Certain theoretical difficulties (connected with recursively defined relations) are discussed, and a proposed proof in LCF is outlined. The emphasis in this work is less on proving original theorems, or even automatically finding proofs of known theorems, than on (i) exhibiting and analysing the underlying structure of proofs, and of machine proof attempts, and (ii) investigating the nature of the interaction (between a user and a computer system) required to generate proofs mechanically; that is, the transition from informal proof plans to behaviours which cause formal proofs to be performed