Backwards State-space Reduction for Planning in Dynamic Knowledge Bases

In this paper we address the problem of planning in rich domains, where knowledge representation is a key aspect for managing the complexity and size of the planning domain. We follow the approach of Description Logic (DL) based Dynamic Knowledge Bases, where a state of the world is represented concisely by a (possibly changing) ABox and a (fixed) TBox containing the axioms, and actions that allow to change the content of the ABox. The plan goal is given in terms of satisfaction of a DL query. In this paper we start from a traditional forward planning algorithm and we propose a much more efficient variant by combining backward and forward search. In particular, we propose a Backward State-space Reduction technique that consists in two phases: first, an Abstract Planning Graph P is created by using the Abstract Backward Planning Algorithm (ABP), then the abstract planning graph P is instantiated into a corresponding planning graph P by using the Forward Plan Instantiation Algorithm (FPI). The advantage is that in the preliminary ABP phase we produce a symbolic plan that is a pattern to direct the search of the concrete plan. This can be seen as a kind of informed search where the preliminary backward phase is useful to discover properties of the state-space that can be used to direct the subsequent forward phase. We evaluate the effectiveness of our ABP+FPI algorithm in the reduction of the explored planning domain by comparing it to a standard forward planning algorithm and applying both of them to a concrete business case study.Comment: In Proceedings GRAPHITE 2014, arXiv:1407.767

Folding Transformation Rules for Constraint Logic Programs

We consider the folding transformation rule for constraint logic programs. We propose an algorithm for applying the folding rule in the case where the constraints are linear equations and inequations over the rational or the real numbers. Basically, our algorithm consists in reducing a rule application to the solution of one or more systems of linear equations and inequations. We also introduce two variants of the folding transformation rule. The first variant combines the folding rule with the clause splitting rule, and the second variant eliminates the existential variables of a clause, that is, those variables which occur in the body of the clause and not in its head. Finally, we present the algorithms for applying these variants of the folding rule

Applying Mean-field Approximation to Continuous Time Markov Chains

The mean-field analysis technique is used to perform analysis of a systems with a large number of components to determine the emergent deterministic behaviour and how this behaviour modifies when its parameters are perturbed. The computer science performance modelling and analysis community has found the mean-field method useful for modelling large-scale computer and communication networks. Applying mean-field analysis from the computer science perspective requires the following major steps: (1) describing how the agents populations evolve by means of a system of differential equations, (2) finding the emergent deterministic behaviour of the system by solving such differential equations, and (3) analysing properties of this behaviour either by relying on simulation or by using logics. Depending on the system under analysis, performing these steps may become challenging. Often, modifications of the general idea are needed. In this tutorial we consider illustrating examples to discuss how the mean-field method is used in different application areas. Starting from the application of the classical technique, moving to cases where additional steps have to be used, such as systems with local communication. Finally we illustrate the application of the simulation and uid model checking analysis techniques

Program Transformation for Development, Verification, and Synthesis of Software

In this paper we briefly describe the use of the program transformation methodology for the development of correct and efficient programs. We will consider, in particular, the case of the transformation and the development of constraint logic programs

Transformational Verification of Linear Temporal Logic

We present a new method for verifying Linear Temporal Logic (LTL) properties of finite state reactive systems based on logic programming and program transformation. We encode a finite state system and an LTL property which we want to verify as a logic program on infinite lists. Then we apply a verification method consisting of two steps. In the first step we transform the logic program that encodes the given system and the given property into a new program belonging to the class of the so-called linear monadic !-programs (which are stratified, linear recursive programs defining nullary predicates or unary predicates on infinite lists). This transformation is performed by applying rules that preserve correctness. In the second step we verify the property of interest by using suitable proof rules for linear monadic !-programs. These proof rules can be encoded as a logic program which always terminates, if evaluated by using tabled resolution. Although our method uses standard program transformation techniques, the computational complexity of the derived verification algorithm is essentially the same as the one of the Lichtenstein-Pnueli algorithm [9], which uses sophisticated ad-hoc techniques

Generalization Strategies for the Verification of Infinite State Systems

We present a method for the automated verification of temporal properties of infinite state systems. Our verification method is based on the specialization of constraint logic programs (CLP) and works in two phases: (1) in the first phase, a CLP specification of an infinite state system is specialized with respect to the initial state of the system and the temporal property to be verified, and (2) in the second phase, the specialized program is evaluated by using a bottom-up strategy. The effectiveness of the method strongly depends on the generalization strategy which is applied during the program specialization phase. We consider several generalization strategies obtained by combining techniques already known in the field of program analysis and program transformation, and we also introduce some new strategies. Then, through many verification experiments, we evaluate the effectiveness of the generalization strategies we have considered. Finally, we compare the implementation of our specialization-based verification method to other constraint-based model checking tools. The experimental results show that our method is competitive with the methods used by those other tools. To appear in Theory and Practice of Logic Programming (TPLP).Comment: 24 pages, 2 figures, 5 table

Proving theorems by program transformation

In this paper we present an overview of the unfold/fold proof method, a method for proving theorems about programs, based on program transformation. As a metalanguage for specifying programs and program properties we adopt constraint logic programming (CLP), and we present a set of transformation rules (including the familiar unfolding and folding rules) which preserve the semantics of CLP programs. Then, we show how program transformation strategies can be used, similarly to theorem proving tactics, for guiding the application of the transformation rules and inferring the properties to be proved. We work out three examples: (i) the proof of predicate equivalences, applied to the verification of equality between CCS processes, (ii) the proof of first order formulas via an extension of the quantifier elimination method, and (iii) the proof of temporal properties of infinite state concurrent systems, by using a transformation strategy that performs program specialization

Program transformation for development, verification, and synthesis of programs

This paper briefly describes the use of the program transformation methodology for the development of correct and efficient programs. In particular, we will refer to the case of constraint logic programs and, through some examples, we will show how by program transformation, one can improve, synthesize, and verify programs

Customer Experience of New Restaurant Concept : Case Frans & Chérie

The objective of this thesis was to analyse customer service quality and customer experience in a restaurant going through a new concept launch. Without any other researches of the topic in the restaurant, this research was to provide an insight for the commissioner into the success of the restaurant concept launch from customers’ point of view. This qualitative survey was conducted by a two-phase customer survey, using two different questionnaires. The first questionnaire was carried out before the concept change in Fransmanni restaurant and the second questionnaire after the change in the new Frans & Chérie Bistro. Therefore, this thesis examined how the expectations towards the new concept Frans & Chérie differed from the actual experience and satisfaction in the restaurant after the change. Hence, the complete research throughout the process of concept change was conducted. Secondary data collection was used to create a framework for the empirical research. The results of the survey indicated, for the most part, good or excellent level of satisfaction with the new Frans & Chérie Bistro. However, the new venue and atmosphere raised controversial opinions on the success of the new concept, along with relevant improvement ideas for the different parts of the customer restaurant experience, such as, stability of food quality and variety of menu, atmosphere, venue décor and music. More experiential parts should be attached to the service in order to increase the customer experience and to achieve the objectives and goals of the Frans & Chérie Bistro according to the results. The results function as a guideline for the restaurant management to improve the new restaurant concept further in order to provide meaningful customer experiences to the customers and ensure high customer service quality.Tämän opinnäytetyön tavoitteena oli analysoida asiakaspalvelun laatua sekä asiakkaiden ravintolakokemusta konseptimuutoksessa uudistetussa Frans & Chérie Bistrossa. Tutkimuksen tarkoituksena oli selvittää, kuinka konseptiuudistus on onnistunut asiakkaiden näkökulmasta, sillä samankaltaista tutkimusta ei ole tehty kyseiseen ravintolakonseptiuudistukseen liittyen. Tutkimus toteutettiin laadullisena tutkimuksena, jossa menetelmänä käytettiin kaksiosaista asiakaskyselyä. Koska tavoitteena oli saavuttaa kokonaisvaltainen tutkimus kyseisen konseptiuudistuksen aikana, ensimmäinen osa kyselyä toteutettiin ennen konseptiuudistusta Fransmanni ravintolassa ja toinen kysely konseptiuudistuksen jälkeen uudessa Frans & Chérie Bistrossa. Tutkimuksessa selvitettiin, kuinka asiakkaiden odotukset uudistunutta ravintolaa kohtaan ennen konseptimuutosta poikkesivat varsinaisesta asiakaskokemuksesta ravintolassa vierailun jälkeen. Tutkimuksen perustana käytettiin kirjallisuutta aiheesta. Tutkimuksen tulokset osoittivat asiakastyytyväisyyden olevan hyvä tai erinomainen uudessa Frans & Chérie Bistrossa. Ravintolan sisustukseen sekä tunnelmaan liittyen tutkimuksen tuloksissa ilmaantui kuitenkin ristiriitaisia mielipiteitä konseptiuudistuksen onnistumisesta. Myös oleellisia parannusehdotuksia tehtiin asiakaskokemuksen kehittämiseksi, koskien ruoan laatua, ruokalistan monipuolisuutta, tunnelmaa, sisustusta sekä musiikkia. Tutkimuksen mukaan Frans & Chérie Bistron ravintolakokemuksen kehittäminen olisi tärkeää, jotta pystyttäisiin saavuttamaan konseptiuudistuksessa asetetut tavoitteet ja luoda asiakkaille ravintolaelämyksiä heidän vieraillessaan ravintolassa. Tutkimuksen tulokset toimivat ravintolan johdon apuna uuden ravintolakonseptin kehittämisessä, jotta he voivat parantaa asiakkaiden ravintolakokemusta sekä varmistaa korkean asiakaspalvelun laadun

Sub-Riemannian heat kernels and mean curvature flow of graphs

We introduce a sub-Riemannian analogue of the Bence-Merriman-Osher diffusion driven algorithm and show that it leads to weak solutions of the horizontal mean curvature flow of graphs over sub-Riemannian Carnot groups. The proof follows the nonlinear semi-group theory approach originally introduced by L. C. Evans in the Euclidean setting and is based on new results on the relation between sub-Riemannian heat flows of characteristic functions of subgraphs and the horizontal mean curvature of the corresponding graphs.Comment: 24 page