35113903
Using semantic networks for data base management
This paper presents a semantic model of data bases. The model assumes the availability of a semantic network storing knowledge about a data base and a set of attributes for the data base. The use of the semantic net in generating a relational schema for the data base, in defining a set of semantic operators and in maintaining the data base consistent is then demonstrated.
12169882
Capturing more world knowledge in the requirements specification
The view is adopted that software requirements involve the representation (modeling) of considerable real-world knowledge, not just functional specifications. A framework (RMF) for requirements models is presented and its main features are illustrated. RMF allows information about three types of conceptual entities (objects, activities, and assertions) to be recorded uniformly using the notion of properties. By grouping all entities into classes or metaclasses, and by organizing classes into generalization (specialization) hierarchies, RMF supports three abstraction principles (classification, aggregation, and generalization) which appear to be of universal importance in the development and organization of complex descriptions. Finally, by providing a mathematical model underlying our terminology, we achieve both unambiguity and the potential to verify consistency of the model.
596050
Building knowledge base management systems

Abstract.Advanced applications in fields such as CAD, software engineering, real-time process control, corporate repositories and digital libraries require the construction, efficient access and management of large, shared knowledge bases. Such knowledge bases cannot be built using existing tools such as expert system shells, because these do not scale up, nor can they be built in terms of existing database technology, because such technology does not support the rich representational structure and inference mechanisms required for knowledge-based systems. This paper proposes a generic architecture for a knowledge base management system intended for such applications. The architecture assumes an object-oriented knowledge representation language with an assertional sublanguage used to express constraints and rules. It also provides for general-purpose deductive inference and special-purpose temporal reasoning. Results reported in the paper address several knowledge base management issues. For storage management, a new method is proposed for generating a logical schema for a given knowledge base. Query processing algorithms are offered for semantic and physical query optimization, along with an enhanced cost model for query cost estimation. On concurrency control, the paper describes a novel concurrency control policy which takes advantage of knowledge base structure and is shown to outperform two-phase locking for highly structured knowledge bases and update-intensive transactions. Finally, algorithms for compilation and efficient processing of constraints and rules during knowledge base operations are described. The paper describes original results, including novel data structures and algorithms, as well as preliminary performance evaluation data. Based on these results, we conclude that knowledge base management systems which can accommodate large knowledge bases are feasible.

5771700
Information services for the Web: building and maintaining domain models
The World Wide Web is serving as a leading vehicle for information dissemination by offering information services, such as product information, group interactions, or sales transactions. Three major factors affect the performance and reliability of information services for the Web: the distribution of information which has resulted from the globalization of information systems, the heterogeneity of information sources, and the sources' instability caused by their autonomous evolution. This paper focuses on integrating existing information sources, available via the Web, in the delivery of information services. The primary objective of the paper is to provide mechanisms for structuring and maintaining a domain model for Web applications. These mechanisms are based on conceptual modeling techniques, where concepts are being defined and refined within a meta-data repository through the use of instantiation, generalization and attribution. Also, active databases techniques are exploited to provide robust mechanisms for maintaining a consistent domain model in a rapidly evolving environment, such as the Web.
35597586
On the Frame Problem in Procedure Specifications
The paper provides examples of situations where formal specifications of procedures in the standard pre/postcondition style become lengthy, cumbersome and difficult to change, a problem which is particularly acute in the case of object oriented specifications with inheritance. We identify the problem as the inability to express that a procedure changes only those things it has to, leaving everything else unmodified, and review some attempts at dealing with this "frame problem" in the software specification community. The second part of the paper adapts a recent proposal for a solution to the frame problem in artificial intelligence-the notion of explanation closure axioms-to provide an approach whereby one can state such conditions succinctly and modularly, with the added advantage of having the specifier be reminded of things that she may have omitted saying in procedure specifications. Since this approach is based on standard predicate logic, its semantics are relatively straightforward. The paper also suggests an algorithm which generates syntactically the explanation closure axioms from the pre/postcondition specifications, provided they are written in a restricted language; it also suggests a model theory supporting it. >
16316493
ToMAS: a system for adapting mappings while schemas evolve
We demonstrate the Toronto Mapping Adaptation System (ToMAS), a tool for automatically detecting and adapting mappings that have become invalid or inconsistent due to changes in either data semantics or schemas. Due to its modular architecture and its stand-alone nature, ToMAS can easily be applied to numerous scenarios and can interoperate with many other tools. To the best of our knowledge, no other tool can correctly maintain the consistency of the mappings under schema changes at the level of complexity supported by ToMAS.
10751686
Experimenting with Linguistic Tools for Conceptual Modelling: Quality of the Models and Critical Features
This paper presents the results of three experiments designed to assess the extent to which a Natural-Language Processing (NLP) tool improves the quality of conceptual models, specifically object-oriented ones. Our main experimental hypothesis is that the quality of a domain class model is higher if its development is supported by a NLP system. The tool used for the experiment – named NL-OOPS – extracts classes and associations from a knowledge base realized by a deep semantic analysis of a sample text. In our experiments, we had groups working with and without the tool, and then compared and evaluated the final class models they produced. The results of the experiments give insights on the state of the art of NL-based Computer Aided Software Engineering (CASE) tools and allow identifying important guidelines to improve their performance, highlighting which of the linguistic tasks are more critical to effectively support conceptual modelling.
9350752
Multi-Agent Architectures as Organizational Structures
A Multi-Agent System (hereafter MAS) is an organization of coordinated autonomous agents that interact in order to achieve common goals. Considering real world organizations as an metaphor, this paper proposes architectural styles for MAS which adopt concepts from organizational theories. The styles are modeled in i*/Tropos, using the notions of actor, goal and actor dependency and are intended to capture needs/wants, delegations and obligations. The proposed architectural styles are evaluated with respect to a set of software quality attributes, such as predictability and adaptability. In addition, we report on a comparative study of organizational and conventional software architectures using a mobile robot control example from the Software Engineering literature. The research reported here was conducted within the scope of the Tropos project, whose objective is to develop a comprehensive agent-oriented software development methodology.
3393049
Data Sharing in the Hyperion Peer Database System
This demo presents Hyperion, a prototype system that supports data sharing for a network of independent Peer Relational Database Management Systems (PDBMSs). The nodes of such a network are assumed to be autonomous PDBMSs that form acquaintances at run-time, and manage mapping tables to define value correspondences among different databases. They also use distributed Event-Condition-Action (ECA) rules to enable and coordinate data sharing. Peers perform local querying and update processing, and also propagate queries and updates to their acquainted peers. The demo illustrates the following key functionalities of Hyperion: (1) the use of (data level) mapping tables to infer new metadata as peers dynamically join the network, (2) the ability to answer queries using data in acquaintances, and (3) the ability to coordinate peers through update propagation.
6657466
Local Relational Model: A Logical Formalization of Database Coordination
We propose a new data model intended for peer-to-peer (P2P) databases. The model assumes that each peer has a (relational) database and exchanges data with other peers (its acquaintances). In this context, one needs a data model that views the space of available data within the P2P network as an open collection of possibly overlapping and inconsistent databases. Accordingly, the paper proposes the Local Relational Model, develops a semantics for coordination formulas. The main result of the paper generalizes Reiter's characterization of a relational database in terms of a first order theory [1], by providing a syntactic characterization of a relational space in terms of a multi-context system. This work extends earlier work by Giunchiglia and Ghidini on Local Model Semantics [2].