Local and Global Properties of the World

The essence of the method of physics is inseparably connected with the problem of interplay between local and global properties of the universe. In the present paper we discuss this interplay as it is present in three major departments of contemporary physics: general relativity, quantum mechanics and some attempts at quantizing gravity (especially geometrodynamics and its recent successors in the form of various pregeometry conceptions). It turns out that all big interpretative issues involved in this problem point towards the necessity of changing from the standard space-time geometry to some radically new, most probably non-local, generalization. We argue that the recent noncommutative geometry offers attractive possibilities, and gives us a conceptual insight into its algebraic foundations. Noncommutative spaces are, in general, non-local, and their applications to physics, known at present, seem very promising. One would expect that beneath the Planck threshold there reigns a ``noncommutative pregeometry'', and only when crossing this threshold the usual space-time geometry emerges.Comment: 43 pages, latex, no figures, changes: authors and abstract added to the body of pape

Geometry, pregeometry and beyond

This article explores the overall geometric manner in which human beings make sense of the world around them by means of their physical theories; in particular, in what are nowadays called pregeometric pictures of Nature. In these, the pseudo-Riemannian manifold of general relativity is considered a flawed description of spacetime and it is attempted to replace it by theoretical constructs of a different character, ontologically prior to it. However, despite its claims to the contrary, pregeometry is found to surreptitiously and unavoidably fall prey to the very mode of description it endeavours to evade, as evidenced in its all-pervading geometric understanding of the world. The question remains as to the deeper reasons for this human, geometric predilection--present, as a matter of fact, in all of physics--and as to whether it might need to be superseded in order to achieve the goals that frontier theoretical physics sets itself at the dawn of a new century: a sounder comprehension of the physical meaning of empty spacetime.Comment: 41 pages, Latex. v2: Date added. v3: Main arguments refined, secondary discussions abridged; expands on the published versio

Taming Numbers and Durations in the Model Checking Integrated Planning System

The Model Checking Integrated Planning System (MIPS) is a temporal least commitment heuristic search planner based on a flexible object-oriented workbench architecture. Its design clearly separates explicit and symbolic directed exploration algorithms from the set of on-line and off-line computed estimates and associated data structures. MIPS has shown distinguished performance in the last two international planning competitions. In the last event the description language was extended from pure propositional planning to include numerical state variables, action durations, and plan quality objective functions. Plans were no longer sequences of actions but time-stamped schedules. As a participant of the fully automated track of the competition, MIPS has proven to be a general system; in each track and every benchmark domain it efficiently computed plans of remarkable quality. This article introduces and analyzes the most important algorithmic novelties that were necessary to tackle the new layers of expressiveness in the benchmark problems and to achieve a high level of performance. The extensions include critical path analysis of sequentially generated plans to generate corresponding optimal parallel plans. The linear time algorithm to compute the parallel plan bypasses known NP hardness results for partial ordering by scheduling plans with respect to the set of actions and the imposed precedence relations. The efficiency of this algorithm also allows us to improve the exploration guidance: for each encountered planning state the corresponding approximate sequential plan is scheduled. One major strength of MIPS is its static analysis phase that grounds and simplifies parameterized predicates, functions and operators, that infers knowledge to minimize the state description length, and that detects domain object symmetries. The latter aspect is analyzed in detail. MIPS has been developed to serve as a complete and optimal state space planner, with admissible estimates, exploration engines and branching cuts. In the competition version, however, certain performance compromises had to be made, including floating point arithmetic, weighted heuristic search exploration according to an inadmissible estimate and parameterized optimization

Review of research in feature-based design

Research in feature-based design is reviewed. Feature-based design is regarded as a key factor towards CAD/CAPP integration from a process planning point of view. From a design point of view, feature-based design offers possibilities for supporting the design process better than current CAD systems do. The evolution of feature definitions is briefly discussed. Features and their role in the design process and as representatives of design-objects and design-object knowledge are discussed. The main research issues related to feature-based design are outlined. These are: feature representation, features and tolerances, feature validation, multiple viewpoints towards features, features and standardization, and features and languages. An overview of some academic feature-based design systems is provided. Future research issues in feature-based design are outlined. The conclusion is that feature-based design is still in its infancy, and that more research is needed for a better support of the design process and better integration with manufacturing, although major advances have already been made

CAD, BIM, GIS and other tricks of the computer science in the education of the Building Engineer

Revisione internazionale- relazione a invito- chair sessione S8T The paper aims to develop some thoughts on the upgrade implemented in the disciplines of drawing from the latest forms of digital representation, commenting on the experiences under way in some university courses included in the learning curriculum provided to engineering students with regard to the course of study in Ingegneria Edile (Building Engineering, also known as Architectural or Construction Engineering) at the Politecnico di Torino. It's a matter of reasoning on what and how to suggest knowledge and practises in the experience of teaching that result as an improvement of skills and abilities appropriate for future commitments required by the job world. Method: Methodological reasons, subject contents and experiences positively carried out during the activities of the course of Representation Techniques and Data Management (in the post graduate "Laurea Magistrale") are treated, focusing on all the resources needed to conduct profitable operations training and first clarifying the specific skills and experience required for the teaching staff, essential qualities to ensure good results: all the activities organized to achieve the training objectives are based on the belief that early training is needed to trigger virtuous review processes for engineering practice and that opportunities to practice through simulations in the academic curriculum for future engineers can produce effects of greater permanence and enable an enhancement of learning outcomes. Result: The analysis, which is addressed primarily to illustrate the result of some of the outcomes of exercise activities leaded by students, brings attention to a solicitation that seems to be constraining and that concerns the system of relations required between operators of the design and construction process, which are requested to enter into shared aims while operating in the specificity of the various technical fields; in this sense, the tricks of the CAD, which is at the service of a geometric knowledge, measured and fulfilled by its attributes, the attention demanded by BIM, which builds a widespread and open network of relationship, the cunnings of the GIS, which has to gather dynamic information and alternative choices, appear to address areas of operational testing following a single purpose directed towards a better characterization of the process of conceptual development and a more advantageous control of the working method. Discussion & Conclusion: So, with the design and over the usual representations, we speak of computer tricks to say that to be understood as the necessary infrastructure to solicit and investigate the reasons of doing and how to solve the complexity of operating on the field, upon which students must impractical themselves to identify qualities and limits, whether they are exploring the reasons of the survey or the reasons bound with the design; certainly a renewal for the most usual ways of designing useful to produce different levels of knowledge and a new shared place for the exchange and discussion of the hypotheses, with what results

Bayesian Economist ... Bayesian Agents I: An Alternative Approach to Optimal Learning

We study the framework of optimal decision making under uncertainty where the agents do not know the full structure of the model and try to learn it optimally. We generalize the results on Bayesian learning based on the martingale convergence theorem to the sequential framework instead of the repeated framework for which results are currently available. We also show that the variability introduced by the sequential framework is sufficient under very mild identifiability conditions to circumvent the incomplete learning results that characterize the literature. We then question the type of convergence so achieved, and give an alternative Bayesian approach whereby we let the economist himself be a Bayesian with a prior on the priors that his agents may have. We prove that such an economist cannot justify endowing all his agents with the same (much less the true) prior on the basis that the model has been running long enough that we can almost surely approximate any agent's beliefs by any other's. We then examine a possibly weaker justification based on the convergence of the economist's measure on beliefs, and fully characterize it by the Harris ergodicity of the relevant Markov kernel. By means of very simple examples, we then show that learning, partial learning, and non-learning may all occur under the weak conditions that we impose. For complicated models where the Harris ergodicity of the Markov kernel in question can neither be proved nor disproved, the mathematical/statistical test of Domowitz and El-Gamal (1989) can be utilized

Negotiated Tutoring: An Approach to Interaction in Intelligent Tutoring Systems

This thesis describes a general approach to tutorial interaction in Intelligent Tutoring Systems, called "Negotiated Tutoring". Some aspects of the approach have been implemented as a computer program in the 'KANT' (Kritical Argument Negotiated Tutoring) system. Negotiated Tutoring synthesises some recent trends in Intelligent Tutoring Systems research, including interaction symmetry, use of explicit negotiation in dialogue, multiple interaction styles, and an emphasis on cognitive and metacognitive skill acquisition in domains characterised by justified belief. This combination of features has not been previously incorporated into models for intelligent tutoring dialogues. Our approach depends on modelling the high-level decision-making processes and memory representations used by a participant in dialogue. Dialogue generation is controlled by reasoning mechanisms which operate on a 'dialogue state', consisting of conversants' beliefs, a set of possible dialogue moves, and a restricted representation of the recent utterances generated by both conversants. The representation for conversants' beliefs is based on Anderson's (1983) model for semantic memory, and includes a model for dialogue focus based on spreading activation. Decisions in dialogue are based on preconditions with respect to the dialogue state, higher level educational preferences which choose between relevant alternative dialogue moves, and negotiation mechanisms designed to ensure cooperativity. The domain model for KANT was based on a cognitive model for perception of musical structures in tonal melodies, which extends the theory of Lerdahl and Jackendoff (1983). Our model ('GRAF' - GRouping Analysis with Frames) addresses a number of problems with Lerdahl and Jackendoff's theory, notably in describing how a number of unconscious processes in music cognition interact, including elements of top-down and bottom-up processing. GRAF includes a parser for musical chord functions, a mechanism for performing musical reductions, low-level feature detectors and a frame-system (Minsky 1977) for musical phrase structures

CAD, BIM, GIS and other tricks of the computer science in the education of the Building Engineer

Revisione internazionale- relazione a invito- chair sessione S8T The paper aims to develop some thoughts on the upgrade implemented in the disciplines of drawing from the latest forms of digital representation, commenting on the experiences under way in some university courses included in the learning curriculum provided to engineering students with regard to the course of study in Ingegneria Edile (Building Engineering, also known as Architectural or Construction Engineering) at the Politecnico di Torino. It’s a matter of reasoning on what and how to suggest knowledge and practises in the experience of teaching that result as an improvement of skills and abilities appropriate for future commitments required by the job world. Method: Methodological reasons, subject contents and experiences positively carried out during the activities of the course of Representation Techniques and Data Management (in the post graduate “Laurea Magistrale”) are treated, focusing on all the resources needed to conduct profitable operations training and first clarifying the specific skills and experience required for the teaching staff, essential qualities to ensure good results: all the activities organized to achieve the training objectives are based on the belief that early training is needed to trigger virtuous review processes for engineering practice and that opportunities to practice through simulations in the academic curriculum for future engineers can produce effects of greater permanence and enable an enhancement of learning outcomes. Result: The analysis, which is addressed primarily to illustrate the result of some of the outcomes of exercise activities leaded by students, brings attention to a solicitation that seems to be constraining and that concerns the system of relations required between operators of the design and construction process, which are requested to enter into shared aims while operating in the specificity of the various technical fields; in this sense, the tricks of the CAD, which is at the service of a geometric knowledge, measured and fulfilled by its attributes, the attention demanded by BIM, which builds a widespread and open network of relationship, the cunnings of the GIS, which has to gather dynamic information and alternative choices, appear to address areas of operational testing following a single purpose directed towards a better characterization of the process of conceptual development and a more advantageous control of the working method. Discussion & Conclusion: So, with the design and over the usual representations, we speak of computer tricks to say that to be understood as the necessary infrastructure to solicit and investigate the reasons of doing and how to solve the complexity of operating on the field, upon which students must impractical themselves to identify qualities and limits, whether they are exploring the reasons of the survey or the reasons bound with the design; certainly a renewal for the most usual ways of designing useful to produce different levels of knowledge and a new shared place for the exchange and discussion of the hypotheses, with what results