Vagueness, Ambiguity, and Underspecification

No abstract

Linda Implementations Using Monitors and Message Passing

Linda is a new parallel programming language that is built around an interprocess communication model called generative communication that differs from previous models in specifying that shared data be added in tuple form to an environment called tuple space, where a tuple exists independently until some process chooses to use it. Interesting properties arise from the model, including space and time uncoupling as well as structured naming. We delineate the essential Linda operations, then discuss the properties of generative communication. We are particularly concerned with implementing Linda on top of two traditional parallel programming paradigms - process communication through globally shared memory via monitors, and process communication in local memory architectures through the use of message passing constructs. We discuss monitors and message passing, then follow with a description of the two Linda implementations

Implementation methodology for using concurrent and collaborative approaches for theorem provers, with case studies of SAT and LCF style provers

Theorem provers are faced with the challenges of size and complexity, fueled by the increasing range of applications. The use of concurrent/ distributed programming paradigms to engineer better theorem provers merits serious investigation, as it provides: more processing power and opportunities for implementing novel approaches to address theorem proving tasks hitherto infeasible in a sequential setting. Investigation of these opportunities for two diverse theorem prover settings with an emphasis on desirable implementation criteria is the core focus of this thesis. Concurrent programming is notoriously error prone, hard to debug and evaluate. Thus, implementation approaches which promote easy prototyping, portability, incremental development and effective isolation of design and implementation can greatly aid the enterprise of experimentation with the application of concurrent techniques to address specific theorem proving tasks. In this thesis, we have explored one such approach by using Alice ML, a functional programming language with support for concurrency and distribution, to implement the prototypes and have used programming abstractions to encapsulate the implementations of the concurrent techniques used. The utility of this approach is illustrated via proof-of-concept prototypes of concurrent systems for two diverse case studies of theorem proving: the propositional satisfiability problem (SAT) and LCF style (first-order) theorem proving, addressing some previously unexplored parallelisation opportunities for each, as follows:. SAT: We have developed a novel hybrid approach for SAT and implemented a prototype for the same: DPLL-Stalmarck. It uses two complementary algorithms for SAT, DPLL and Stalmarck’s. The two solvers run asynchronously and dynamic information exchange is used for co-operative solving. Interaction of the solvers has been encapsulated as a programming abstraction. Compared to the standalone DPLL solver, DPLL-Stalmarck shows significant performance gains for two of the three problem classes considered and comparable behaviour otherwise. As an exploratory research effort, we have developed a novel algorithm, Concurrent Stalmarck, by applying concurrent techniques to the Stalmarck algorithm. A proof-of-concept prototype for the same has been implemented. Implementation of the saturation technique of the Stalmarck algorithm in a parallel setting, as implemented in Concurrent Stalmarck, has been encapsulated as a programming abstraction. LCF: Provision of programmable concurrent primitives enables customisation of concurrent techniques to specific theorem proving scenarios. In this case study, we have developed a multilayered approach to support programmable, sound extensions for an LCF prover: use programming abstractions to implement the concurrent techniques; use these to develop novel tacticals (control structures to apply tactics), incorporating concurrent techniques; and use these to develop novel proof search procedures. This approach has been implemented in a prototypical LCF style first-order prover, using Alice ML. New tacticals developed are: fastest-first; distributed composition; crossTalk: a novel tactic which uses dynamic, collaborative information exchange to handle unification across multiple sub-goals, with shared meta-variables; a new tactic, performing simultaneous proof-refutation attempts on propositional (sub- )goals, by invoking an external SAT solver (SAT case study), as a counter-example finder. Examples of concrete theorem proving scenarios are provided, demonstrating the utility of these extensions. Synthesis of a variety of automatic proof search procedures has been demonstrated, illustrating the scope of programmability and customisation, enabled by our multilayered approach

Teaching language as metaphor:: the potential of current research into metaphor and cognition for classroom practice

Recent developments in cognitive linguistics have revealed how abstract meaning in language is shaped by bodily experience. We understand and express such concepts as time, causation, direction or love through metaphors that are shaped out of our sense of ourselves as embodied creatures (Lakoff 1987, Johnson 1989, 1991, 1992, 1993). The diachronic analysis of syntax also shows how metaphor shifts lexical meaning towards grammatical meaning (Heine 1997). For example, in English and other Indo-European languages, we use what Heine (1993) identifies as a propositional schema of possession to express how in having taken hold of an action, we have completed it. Thus we grammaticalise a possessive 'have' (haber, avoir, etc.) or 'ter' (hold in Portuguese) to express an immediate past, or finally, as in modem French, the past itself Applied linguists are now asking how this cognitivist re-examination of the nature of meaning creation should impact upon language teaching (e.g. Low 1988, Lindostromberg 1991, Dudley Evans and St John 1998, and Boers 2000). One suggestion is that conceptual metaphors might prove an effective mechanism to help learners of specialist language group some forms of specialist lexis, using a conceptual metaphor such as 'cash is liquid', for example, to help students understand the language of finance, clustering and organising such terms as 'capital liquidity' and 'company floatation’. This thesis carries forward this exploration in a more comprehensive manner. It first examines the nature of metaphor in order to produce a useable construct. This construct differs from some mainstream cognitive views (e.g. Gibbs 1994 and Lakoff and Johnson 1999) in that it follows Glucksberg and Keysar (1993) in relating metaphor construction to class inclusion, and Glucksberg and McClone (1999) in affording similarity a role in metaphor interpretation. It treats metaphor as holding together three aspects of pedagogy: the nature of what is taught, the mechanisms through which it is learnt, and the learner's affective relationship to both. The picture of language and the language learner's mind that is produced rejects notions of adult acquisition and focuses upon the role of conscious learning through metaphor-based techniques. In the role of a participant observer, the author recounts how they implemented this in the classroom

An analysis of the application of AI to the development of intelligent aids for flight crew tasks

This report presents the results of a study aimed at developing a basis for applying artificial intelligence to the flight deck environment of commercial transport aircraft. In particular, the study was comprised of four tasks: (1) analysis of flight crew tasks, (2) survey of the state-of-the-art of relevant artificial intelligence areas, (3) identification of human factors issues relevant to intelligent cockpit aids, and (4) identification of artificial intelligence areas requiring further research

Universal Dynamics, a Unified Theory of Complex Systems. Emergence, Life and Death

A universal framework is proposed, where all laws are regularities of relations between things or agents. Parts of the world at one or all times are modeled as networks called SYSTEMS with a minimum of axiomatic properties. A notion of locality is introduced by declaring some relations direct (or links). Dynamics is composed of "atomic" constituents called mechanisms. They are conditional actions of basic local structural transformations (``enzymes''): indirect relations become direct (friend of friend becomes friend), links are removed, objects copied. This defines a kind of universal chemistry. I show how to model basic life processes in a self contained fashion as a kind of enzymatic computation. The framework also accommodates the gauge theories of fundamental physics. Emergence creates new functionality by cooperation - nonlocal phenomena arise out of local interactions. I explain how this can be understood in a reductionist way by multiscale analysis (e.g. renormalization group).Comment: 57 pages, 7 figure

The knowing ear : an Australian test of universal claims about the semantic structure of sensory verbs and their extension into the domain of cognition

In this paper we test previous claims concerning the universality of patterns of polysemy and semantic change in perception verbs. Implicit in such claims are two elements: firstly, that the sharing of two related senses A and B by a given form is cross-linguistically widespread, and matched by a complementary lack of some rival polysemy, and secondly that the explanation for the ubiquity of a given pattern of polysemy is ultimately rooted in our shared human cognitive make-up. However, in comparison to the vigorous testing of claimed universals that has occurred in phonology, syntax and even basic lexical meaning, there has been little attempt to test proposed universals of semantic extension against a detailed areal study of non-European languages. To address this problem we examine a broad range of Australian languages to evaluate two hypothesized universals: one by Viberg (1984), concerning patterns of semantic extension across sensory modalities within the domain of perception verbs (i .e. intra-field extensions), and the other by Sweetser (1990), concerning the mapping of perception to cognition (i.e. trans-field extensions). Testing against the Australian data allows one claimed universal to survive, but demolishes the other, even though both assign primacy to vision among the senses