Transformation-Based Bottom-Up Computation of the Well-Founded Model

We present a framework for expressing bottom-up algorithms to compute the well-founded model of non-disjunctive logic programs. Our method is based on the notion of conditional facts and elementary program transformations studied by Brass and Dix for disjunctive programs. However, even if we restrict their framework to nondisjunctive programs, their residual program can grow to exponential size, whereas for function-free programs our program remainder is always polynomial in the size of the extensional database (EDB). We show that particular orderings of our transformations (we call them strategies) correspond to well-known computational methods like the alternating fixpoint approach, the well-founded magic sets method and the magic alternating fixpoint procedure. However, due to the confluence of our calculi, we come up with computations of the well-founded model that are provably better than these methods. In contrast to other approaches, our transformation method treats magic set transformed programs correctly, i.e. it always computes a relevant part of the well-founded model of the original program.Comment: 43 pages, 3 figure

Providing Context-sensitive Access to the Earth Observation Product Library

The German Remote Sensing Data Center (DFD) has developed a digital library for the long-term management of earth observation data products. This Product Library is a central part of DFD’s multi-mission ground segment Data and Information Management System (DIMS) currently hosting one million digital products, corresponding to 150 Terabyte of data. Its data model is regularly extended to support products of upcoming earth observation missions. The ever increasing complexity led to the development of operating interfaces which use a-priori and context knowledge, allowing efficient management of the dynamic library content. This paper presents the development and operating of context-sensitive library access tools based on meta modeling and online grammar interpretation

A Hypertext-Based Tool for Large Scale Software Reuse

. A hypertext-based interactive tool supporting the management of large software libraries is presented. We claim that a simple, pragmatic approach to software reuse is best suited to aid the software engineer in solving the practical problems of software configuration from reusable components. When developing the system described in this paper emphasis has been put on the semi-automatic classification and interactive retrieval of components and their descriptions. The system has been installed at the BMW automobile manufacturing facilities in Munich. First experiences show good usability and acceptance. Keywords: software reuse, hypertext, software configuration, reusable components, software re-engineering, taxonomic classification. 1 Introduction Component reuse is a theme of growing importance as regards the productivity as well as the quality of software development. Reuse is of course not limited to program code but covers all levels of the software production process, such as p..

Extending Deductive Database Languages by Embedded Implications

this paper can be characterized as follows

A Deductive Database Language Supporting Modules

The applicability of programming languages for knowledge based systems to real life application problems is largely determined by their support of modularity, abstraction, and reusability of modules. While the deductive database approach to knowledge representation has its merits in the declarativity of the underlying logic languages and the integration of deduction and efficient database access, it currently does not offer structuring instruments and abstraction facilities. In this paper we propose a way to incorporate modules and data abstraction into a deductive database language, essentially without deviating from pure logic, i.e. the majority of our concepts are supported by the underlying logic language itself

The deductive database system LOLA

The LOLA system has been designed as the query answering component of a deductive database system and integrates ideas from logic programming and relational query processing. LOLA is based on a clausal logic programming language with function symbols, negation, grouping and aggregation, special predicate