Developments from enquiries into the learnability of the pattern languages from positive data

AbstractThe pattern languages are languages that are generated from patterns, and were first proposed by Angluin as a non-trivial class that is inferable from positive data [D. Angluin, Finding patterns common to a set of strings, Journal of Computer and System Sciences 21 (1980) 46–62; D. Angluin, Inductive inference of formal languages from positive data, Information and Control 45 (1980) 117–135]. In this paper we chronologize some results that developed from the investigations on the inferability of the pattern languages from positive data

Indexing principles for relational languages applied to PROLOG code generation

In this paper we propose an extensible, flexible, multi-argument indexing technique for relational languages. We present a compiler producing indexing header code for a PROLOG emulator based on the Warren Abstract Machine. We will show that our technique combines positive aspects of relational database methods and other existing WAM-based indexing schemes. All the indexing concepts introduced are implemented in LISP for the relational-functional programming language RELFUN

Declarative theorem proving for operational semantics

iAbstract The aim of this Masters Thesis is to propose to SYSteam Nät AB, a local Internet Service Provider (ISP) in Uppsala, Sweden, how to implement IP telephony in their existing IT-infrastructure as a service to their customers. Thus the perspective of the thesis will be that of a local Internet Service Provider. Three general areas are covered in the thesis: Market and Business Model, Technology, and Economics. Important issues for SYSteam Nät AB as an established local broadband Internet Service Provider are to both retain present customers and to attract new customers. Some believe that offering value added services such as IP telephony could do this. Implementation of IP telephony can be done in different ways to fulfil SYSteam Nät’s requirements. The analysis leads to a proposal of how SYSteam Nät could implement IP telephony. This involves many multi-faceted business, technical, and financial issues; each aspect is examined in this thesis. ii Sammanfattnin

Goal driven theorem proving using conceptual graphs and Peirce logic

The thesis describes a rational reconstruction of Sowa's theory of Conceptual Graphs. The reconstruction produces a theory with a firmer logical foundation than was previously the case and which is suitable for computation whilst retaining the expressiveness of the original theory. Also, several areas of incompleteness are addressed. These mainly concern the scope of operations on conceptual graphs of different types but include extensions for logics of higher orders than first order. An important innovation is the placing of negation onto a sound representational basis. A comparison of theorem proving techniques is made from which the principles of theorem proving in Peirce logic are identified. As a result, a set of derived inference rules, suitable for a goal driven approach to theorem proving, is developed from Peirce's beta rules. These derived rules, the first of their kind for Peirce logic and conceptual graphs, allow the development of a novel theorem proving approach which has some similarities to a combined semantic tableau and resolution methodology. With this methodology it is shown that a logically complete yet tractable system is possible. An important result is the identification of domain independent heuristics which follow directly from the methodology. In addition to the theorem prover, an efficient system for the detection of selectional constraint violations is developed. The proof techniques are used to build a working knowledge base system in Prolog which can accept arbitrary statements represented by conceptual graphs and test their semantic and logical consistency against a dynamic knowledge base. The same proof techniques are used to find solutions to arbitrary queries. Since the system is logically complete it can maintain the integrity of its knowledge base and answer queries in a fully automated manner. Thus the system is completely declarative and does not require any programming whatever by a user with the result that all interaction with a user is conversational. Finally, the system is compared with other theorem proving systems which are based upon Conceptual Graphs and conclusions about the effectiveness of the methodology are drawn

Classification-based phrase structure grammar: an extended revised version of HPSG

This thesis is concerned with a presentation of Classification -based Phrase Structure Grammar (or cPSG), a grammatical theory that has grown out of extensive revisions of, and extensions to, HPSG. The fundamental difference between this theory and HPSG concerns the central role that classification plays in the grammar: the grammar classifies strings, according to their feature structure descriptions, as being of various types. Apart from the role of classification, the theory bears a close resemblance to HPSG, though it is by no means a direct translation, including numerous revisions and extensions. A central goal in the development of the theory has been its computational implementation, which is included in the thesis.The presentation may be divided into four parts. In the first, chapters 1 and 2, we present the grammatical formalism within which the theory is stated. This consists of a development of the notion of a classificatory system (chapter 1), and the incorporation of hierarchality into that notion (chapter 2).The second part concerns syntactic issues. Chapter 3 revises the HPSG treatment of specifiers, complements and adjuncts, incorporating ideas that specifiers and complements should be distinguished and presenting a treatment of adjuncts whereby the head is selected for by the adjunct. Chapter 4 presents several options for an account of unbounded dependencies. The accounts are based loosely on that of GPSG, and a reconstruction of GPSG's Foot Feature Principle is presented which does not involve a notion of default. Chapter 5 discusses coordination, employing an extension of Rounds- Kasper logic to allow a treatment of cross -categorial coordination.In the third part, chapters 6, 7 and 8, we turn to semantic issues. We begin (Chapter 6) with a discussion of Situation Theory, the background semantic theory, attempting to establish a precise and coherent version of the theory within which to work. Chapter 7 presents the bulk of the treatment of semantics, and can be seen as an extensive revision of the HPSG treatment of semantics. The aim is to provide a semantic treatment which is faithful to the version of Situation Theory presented in Chapter 6. Chapter 8 deals with quantification, discussing the nature of quantification in Situation Theory before presenting a treatment of quantification in CPSG. Some residual questions about the semantics of coordinated noun phrases are also addressed in this chapter.The final part, Chapter 9, concerns the actual computational implementation of the theory. A parsing algorithm based on hierarchical classification is presented, along with four strategies that might be adopted given that algorithm. Also discussed are some implementation details. A concluding chapter summarises the arguments of the thesis and outlines some avenues for future research

Fourth Annual Workshop on Space Operations Applications and Research (SOAR 90)

The proceedings of the SOAR workshop are presented. The technical areas included are as follows: Automation and Robotics; Environmental Interactions; Human Factors; Intelligent Systems; and Life Sciences. NASA and Air Force programmatic overviews and panel sessions were also held in each technical area

The Application of Expert Systems to Small Scale Map Designs

The increased availability of inexpensive computer mapping programs in recent years has lead to a great increase in the number of map authors and the number of maps being produced, but does not however appear to have lead to more widespread knowledge of cartographic design theory. The large number of poorly designed maps created by users of these computer systems indicates that there is a lack of knowledge of how to design maps. These poorly designed maps are not the fault of the computer programs, since most programs do have the capability of producing well designed maps when used by someone knowledgeable in map design. Rather, the problem lies with map authors who are not skilled in cartographic design and who would probably never produce a map by conventional means, but would contract a cartographer to produce it. What is required are programs to be used by naive map authors that are better able to produce reasonably well designed maps, or at least maps which do not break the most fundamental rules of map design. The area of computer science devoted to producing programs that include knowledge of how an expert solves a problem is that of Expert Systems. An Expert System is essentially a program which includes a codified form of the rules that an expert uses to solve a problem. Thus a cartographic design expert system would include the rules a cartographer uses when designing a map. This study examines the fields of artificial intelligence and expert system to assess how they may best be applied to the map design problem. A comprehensive review of the application of expert systems in design, mapping generally and map design in particular is also provided. In order to develop an expert system, the problem or 'domain' must be defined in a relatively formal manner. A structure for describing geographic information and cartographic representation is developed and a model of the cartographic design process for application in expert systems is also described. Based on the models developed, a functional specification for a cartographic design expert system for small scale maps is produced, with the rules required for each stage in the design process being set out. The development of an expert system, written in Prolog, incorporating these rules is then described in some detail. Details of how the Prolog language can be applied to a specific problem, colouring the political map, are also given. It has been found that as long as realistic goals are set and that the system is limited either in scale or range of topics, it is possible to develop an operational cartographic design expert system. However, it must be recognised that a considerable amount of further development will be needed to bring such a system to market with the support structures and robustness that this entails