Abstract not found

Abstract not found

data types are facilitated in Godel by its type and module systems. Thus, in order to describe the meta-programming facilities of Godel, a brief account of these systems is given. Each constant, function, predicate, and proposition in a Godel program must be specified by a language declaration. The type of a variable is not declared but inferred from its context within a particular program statement. To illustrate the type system, we give the language declarations that would be required for the program in Figure 1. BASE Name. CONSTANT Tom, Jerry : Name. PREDICATE Chase : Name * Name; Cat, Mouse : Name. Note that the declaration beginning BASE indicates that Name is a base type. In the statement Chase(x,y) !- Cat(x) & Mouse(y). the variables x and y are inferred to be of type Name. Polymorphic types can also be defined in Godel. They are constructed from the base types, type variables called parameters, and type constructors. Each constructor has an arity 1 attached to it. As an...

We discuss a declarative characterization of inheritance in logic programming. Our approach is inspired both by existing literature on denotational models for inheritance and by earlier work on a compositional definition of the semantics of logic Programming. We consider a general form of inheritance which is defined with an overriding semantics between inherited definitions and incorporates two different mechanisms known in the literature as static and dynamic inheritance. The result of our semantic reconstruction is an elegant framework which enables us to capture the compositional properties of inheritance and offers a uniform basis for the analysis of the different mechanisms we consider. 1

In this review of metaprogramming in logic we pay equal attention to theoretical and practical issues: the contents range from mathematical and logical preliminaries to implementation and applications in, e.g., software engineering and knowledge representation. The area is one in rapid development but we have emphasized such issues that are likely to be important for future metaprogramming languages and methodologies. 1 Introduction The term `metaprogramming' relates to `programming' as `metalanguage' relates to `language' and `metalogic' to `logic': programming where the data represent programs. It should be no surprise that metaprogramming with logic programming languages takes advantage of many results from metalogic. In the most general interpretation we would say that `metaprogramming ' refers to any kind of computer programming where the input or output represents programs. We will refer to a program of this kind as a metaprogram and to its data as object programs. Analogousl...

. In this paper, we reconsider the problem of specialising the vanilla meta interpreter through fully automatic and completely general partial deduction techniques. In particular, we study how the homeomorphic embedding relation guides specialisation of the interpreter. We focus on the so-called parsing problem, i.e. removing all parsing overhead from the program, and demonstrate that further refinements in the control of general partial deduction are necessary to properly deal with it. In particular, we modify local control on the basis of information imported from the global level. The resulting control strategy, while remaining fully general, leads to excellent specialisation of vanilla like meta programs. Parsing is always specialised, but -- appropriately, as we will show -- not always completely removed. As a concrete application, we subject an extended vanilla meta interpreter capable of dealing with compositions of programs to our techniques, showing we equal or surpass results obtained through a more ad hoc approach. 1

In this paper we propose a semantics for first order modular (open) programs. Modular programs are built as a combination of separate modules, which may evolve separately, and be verified separately. Therefore, in order to reason over such programs, compositionality plays a crucial role: the semantics of the whole program must be obtainable as a simple function from the semantics of its individual modules. In this paper we propose such a compositional semantics for first-order programs. This semantics is correct with respect to the set of logical consequences of the program. Moreover, -- in contrast with other approaches -- it is always computable. Furthermore, we show how our results on first-order programs may be applied in a straightforward way to normal logic programs, in which case our semantics might be regarded as a compositional counterpart of Kunen's semantics. Finally we discuss and show how these results have to be modified in order to be applied to normal CLP. 1 Introduct...

Using constraint logic techniques, it is made possible to use a wellknown metainterpreter backwards as a device for generating programs. A metainterpreter is developed, which provides a sound and complete implementation of the binary demo predicate. Based on it, a general methodology for automated reasoning is proposed and it turns out that a wide range of reasoning tasks, normally requiring different systems, can be defined in a concise manner in this framework. Examples are shown of abductive and inductive reasoning in the usual first-order setting as well as in contexts of default reasoning and linear logic. Furthermore, examples of diagnosis and natural language analysis are shown. 1

Arguably, model theory serves two main functions: (1) to explain the relationship between language and experience, and (2) to specify the notion of logical consequence. In this paper I shall propose the notion of `knowledge assimilation', the assimilation of new information into a knowledge base, as an alternative understanding of the way in which a knowledge base formulated in logic relates to externally generated input sentences that describe experience. I shall argue that the notion of logical consequence can also be understood within a knowledge assimilation framework, in terms of sentences that must hold no matter what stream of input sentences might arise in the future. Classical model theory can be understood as dealing with static relationships among individuals. It leads naturally therefore to possible world semantics and modal logic, in which models are understood as related to one another by accessibility relations. I shall argue in favour of a non-model-theoretic alternativ...

We present the basic principles and possible applications of systems capable of meta-reasoning and reflection. After a discussion of the seminal approaches, we outline our own perception of the state of the art, mainly but not only in computational logic and logic programming. We review relevat successful...