Abstract: The term “ agent ” has became a buzzword these days, not only in academic circles, but also in some computer magazines and application fields of computer science like manufacturing and logistics. Hence, there is a pressing need for a design methodology for multi-agent systems. Or even stronger, there is a demand for an agent engineering technology, which includes computer assistance during the design phases, for the validation of the designed system, and for the implementation of the multi-agent system as a physically distributed system. This status report will introduce the field of multi-agent systems and its design. Three prominent applications will serve as a first motivation of the theme. Based on the ideas of the agent examples a discussion on the term agent will serve as a first motivation of the theme. Based of the theme. Based on the ideas of the agent architecture of an agent, its communication capabilities, and planning in a multi-agent context. After this broad technical introduction the main topic of this work will be tackled. An introduction to five methodologies for the design of multi-agent systems will be given and a new one, the AWIC method, will be presented. Eventually a brief discussion about the multi-agent design approaches will be given, the missing correlations to the task definitions will be critizised, and further research directions will be proposed.

Abstract: A time-dependent concept is a conceptual entity that is defined in terms of temporal relationships with other entities. For example, the concept of an action is defined in terms of a set of temporal relationships among states of a system. The concept of “widow”, in natural language, is defined in terms of events that have occurred in the past. Time-dependent concepts appear in several application areas, from natural language to diagnosis, from planning to data mining. An interesting issue in knowledge representation is how to formally represent and reason with these concepts. In this paper, we represent a family of formal representation languages obtained as an interval-based temporal extension of description logics . We illustrate the expressiveness of these formalisms in representing time-dependent concepts with respect to standard description logics and other extensions. We give some complexity results for reasoning problems and we propose approximate algorithms to compute subsumption among time-dependent concepts.

Abstract: Modeling the interactions among the objects in an application domain and the activities in the domain are necessary extensions of modeling the structure and behaviour of objects in the domain. Object models capture the structure and behaviour of components in the application domains. Interaction models describe how the components in the domain interact to realize the activities in the domain. Activity models are used to describe the functionality of the domain. The integration of object, interaction and activity models is essential for producing complete domain models which we refer to as Component-Interaction-Activity (CIA) models. The CIA model of a domain simplifies the development of applications in that domain because it makes extensive reuse of the elements of the domain possible. Concepts for developing the CIA models of application domains are described. A Domain Modeling Language (DML) which provides constructs for expressing the concepts in CIA models is introduced. The DML provides: (i) a class construct to define components, (ii) rule, trigger, event and relationship constructs to define interactions among components, and (iii) process and task constructs to define the activities in the domain. A Domain Modeling Tool which provides a graphic interface to DML and makes the CIA domain models expressed in DML executable is introduced. An example of using CIA models in developing applications is presented.

Abstract: Our goal is to work out an integration process which makes it possible to give a global design schema obtained from several schemas, each of them describing the same reality viewed in different ways, in order to obtain the fullest view. Problems and conflicts arise during the schema integration. They are due to the several ways of representing the semantic knowledge and of structuring knowledge (using the same design model). When the detection and solution of structural problems are model dependent, the detection and solution of semantic problems are not model dependent. To represent the semantic of the words which are used in a schema, we have defined a model of a thesaurus drawn from the domain dealing with the meaning of words: linguistics. In this paper, we will show the interest in using this fuzzy thesaurus when design schema are being integrated.

Abstract: In an information system a key role is played by the underlying data schema. This article starts out from the view that the entire modelling process of an information system''s data schema can be seen as a schema transformation process. A transformation process that starts out with an initial draft conceptual schema and ends with an internal database schema for some implementation platform. This allows us to describe the transformation process of a database design as an evolution of a schema through a universe of data schemas. Doing so, allows for a better understanding of the actual design process, countering the problem of ''software development under the lamppost''. Even when the information system design is finalised, the data schema can evolve further due to changes in the requirements on the system. We present a universe of data schemas that allows us to describe the underlying data schemas at all stages of their development. This universe of data schemas is used as a case study on how to describe the complete evolution of a data schema with all its relevant aspects. The theory is general enough to cater for more modelling concepts, or different modelling approaches. To actually model the evolution of a data schema, we present a versioning mechanism that allows us to model the evolutions of the elements of data schemas and their interactions, leading to a better understanding of a schema design process as a whole. Finally, we also discuss the relationship between this simple versioning mechanism and general purpose version management systems.

Abstract: This paper addresses the problem of view integration in a CASE tool environment which is aiming at the elaboration of a conceptual schema of an application. The previous integration tools were mainly based on syntax and structure comparisons. A new generation of intelligent tools is now arising, assuming that view integration algorithms must also capture the deep semantics of the objects represented in the views. Dealing with the semantics of the objects is now a realistic objective, thanks to the research results obtained in the natural language area. This paper presents the definition of a view integration algorithm enhanced by the use of linguistic knowledge. This algorithm mainly consists of a semantic unification of views which are described using an extended entity-relationship model. It is combined with natural language techniques such as Fillmore's semantic cases and Sowa's conceptual graphs, supported by semantic dictionaries.

Abstract: As conceptual models are both the result of and subject to communication between domain experts and information analysts, it is of the highest importance to explicitly relate conceptual models to the language in which they are communicated. To achieve this, we identify a set of semantic primitives in a suitable conceptual modelling framework and present the prototype of a knowledge extraction tool which helps analysts to find useful primitives in free natural language texts. In addition we suggest possible extensions of the presented approach to other phases of conceptual modelling.

Abstract: As conceptual models reflect people's perception of real-world phenomena, they are closely tied to the way people describe and talk about these phenomena in natural language. The models, used for developing database and information systems and for presenting or explaining databases, usually include linguistic notions to help interpret their contents. In this paper, we show how linguistic knowledge from a semantically based lexicon can be used to check the quality of conceptual models. The check is a natural extension of traditional verification checks, and its purpose is to ensure that words and phrases included in the models are used in a linguistically meaningful way. Linguistic expressions must be of the correct type, and the relationships between expressions in the model must be acceptable with respect to the semantic constraints indicated in the lexicon.

Abstract: This article presents the linguistic level of KHEOPS, describing its structure and the information it contains. Even though natural language specification interfaces are a main aspect of the KHEOPS environment we limit our discussion to the paraphrasing, view integration, and schema reuse aspects, presenting their main characteristics and how they make use of the said level. In fact, the major problem in these procedures, is the need to understand the schema semantics. To help in this sense, the linguistic level of KHEOPS offers semantic relations, Fillmore's semantic cases and Sowa's conceptual graphs stored in semantic electronic dictionaries.

Abstract: Production rules are useful for several tasks in active database systems, such as integrity constraint checking, derived data maintenance, database state monitoring, etc. Furthermore, production rules can express knowledge in a high-level form for problem solving in Knowledge Base Systems (KBS). Present active object-oriented database (OODB) systems traditionally provide event-driven rules which are triggered by events, i.e. database modifications. This paper describes DEVICE, a high-level rule integration scheme in an active OODB system, resulting in an active KBS. The paper emphasises the run-time processing of production rules, namely the incremental matching of rule conditions, as well as rule selection and firing. The matching of production rules requires special algorithms based on the flow of updated data through a discrimination network, like RETE, TREAT, etc. DEVICE offers a smooth integration of production rules into an active OODB system that only supports event-driven rules, without introducing new data structures, maintaining at the same time the properties of discrimination networks. This is achieved using complex events to map the conditions of production rules and monitor the database to incrementally match those conditions. DEVICE maps each production rule into one event-driven rule that is easy to maintain and offers centralised rule selection control for correct run-time behaviour and conflict resolution. Furthermore, DEVICE provides the infrastructure for the integration of various other rule paradigms into a single KBS, like deductive rules and integrity constraints and leaves room for the optimisation of the matching process through variations of the basic discrimination network.

Abstract: In this paper we present a rule-based database language known as CDOL (Comprehensive, Declarative Object Language) that is an integration of deductive, object-oriented and active database technology. CDOL provides sublanguages for the expression of derived data, constraints, updates and active rules. The rule-based query language of CDOL provides an expressive approach to extend the stored database with derived attributes and classes. The constraint sublanguage allows explicit declarative specification of integrity constraints as a basis for database consistency. The update sublanguage of CDOL enables ad-hoc declarative update requests, where updates are encapsulated in the methods associated with class definitions, thus conforming to traditional objectoriented design concepts. The active rule sublanguage provides active, user-transparent agents that support reactive behavior within CDOL applications. In particular, active rules can be used to supplement declarative updates to maintain database consistency with respect to the set of integrity constraints. Active rules in general are used to monitor the occurrence of specific events and to serve as alerters and triggers within a CDOL application. This paper presents the rule-based query language of CDOL and illustrates the manner in which the constraint, update and active rule sublanguages build on this declarative framework. The use of methods and transactions are also addressed, together with a discussion of the operational semantics of active rule processing.

Abstract: Two major problems in schema integration are to identify correspondences between different conceptual schemas and to verify that the proposed correspondence are consistent with the semantics of the schemas. These problems can only be effectively addressed if the schemas are expressed in a semantically rich modelling formulation. We introduce such a modelling formalism that utilises linguistic instruments, in particular case grammar and speech act theory. We also show how this formalism can be used in a heuristic method for identifying schema correspondences.

Abstract: During the process of knowledge acquisition from different experts it is usual that contradictions occur. Therefore strategies are needed for dealing with divergent statements and conflicts. We provide a formal framework to represent, process and combine distributed knowledge. The representation formalism is many-valued logic, which is a widely accepted method for expressing uncertainty, vagueness, contradictions and lack of information. Combining knowledge as proposed here makes use of the bilattice approach, which turns out to be very flexible and suggestive in the context of combining divergent information. We give some guidelines for choosing truth value spaces, assigning truth values and defining global operators to encode integration strategies.

Abstract: Integrity maintenance is essential in integrated engineering information systems because the behaviour of the whole system becomes unpredictable unless the integrity of the shared data is properly maintained. However, validation of integrity is often very expensive because it requires lots of cross references of entity instances of the same type or different types, which should be retrieved from database systems in a shared database environment. One of the goals of this work is to minimize the number of database accesses in validating a set of integrity constraints. A heterogeneous database environment is built using EXPRESS as a global schema language. EXPRESS is an international standard information modelling language which was developed for STEP (STandard for the Exchange of Product data). Based on a set of database interface functions, evaluation sequences are determined by analysing the data dependencies among database accesses required for integrity validation.

Abstract: In this paper we illustrate how information on behaviour can be captured from natural language with the RADD-NLI. The behavioural information contained in verbal descriptions of processes is transformed into the RADD-NLI process model of characteristic processes. This process model is then integrated into the knowledge base of the RADD-NLI. Although taken from a specific domain this model is abstract enough to form the basis for further applications with synonym relations. Processes coming up in the user dialogue will be matched against the knowledge base. A dialogue control is activated if a mismatch occurs or for a detailed discussion of captured processes with the user. Linguistic knowledge, especially antonymous verb pairs, is considered to decide whether a captured process will be integrated into the structural database design and/or the process list of the design.

Abstract: This paper describes a vision in which linguistic knowledge and theories are introduced into conceptual modeling, and it sums up the advantages achieved by this approach. We will show how the extension of conceptual modeling techniques with linguistic theories increases their expressive power, the capability to formalize well-known conceptual aspects, like object roles and constraints, and their internal consistency. Furthermore, we will explain the advantages gained from using such an extended conceptual modeling technique by describing the adjustments and improvements of the modeling process itself and the extensions to the validation and verification process of the sophisticated models. We will demonstrate this approach by introducing a linguistically based modeling environment, Color-X .

Abstract: In the early phases of requirements engineering, inspecting previously constructed conceptual models is important both for reusing specifications and for gaining general knowledge about how similar problems have been solved in other projects. However, as the users at this stage have only vague ideas about the system to be implemented, they are seldom able to specify a query to the CASE repository that is precise enough to capture the relevant conceptual models. In this paper, we present an information retrieval approach that frees the user from knowing the details of the modeling languages used in the repository and helps him retrieve models from other domains that are structurally similar to the one he intends to build. The system exploits the linguistic, semantic properties of the query to suggest what kind of representation he should look for, and it afterwards retrieves all models that are consistent with the query structure and the semantic representations of the words included in the query.

Abstract: The formalisation of rational agents is a topic of continuing interest in Artificial Intelligence. Research on this subject has held the limelight ever since the pioneering work of Moore [1980; 1984] in which knowledge and actions are considered. Over the years important contributions have been made on both informational aspects like knowledge and belief (for a survey see [Halpern and Moses, 1992; Meyer and van der Hoek, 1995]), and motivational 1 aspects like commitments and obligations [Cohen and Levesque, 1990]. Recent developments include the work on agent-oriented programming [Shoham, 1993], the Belief-Desire-Intention architecture [Rao and Georgeff, 1991], logics for the specification and verification of multi-agent systems [Wooldridge and Fisher, 1992], and cognitive robotics [Lesperance et al., 1994].

Abstract: A semantic image database system (OISDBS) has been designed for structural management of image data. A semantic image data model has been presented to describe the inner structure and contexts of images. A diagrammatic query language with a QBE (Query-by-example) flavor is proposed together with a discussion of its foundation on object rewriting. This data model describes the structure and contents of images by incorporating type constructors, functions on types, and inheritance. It supports composite modeling for entities which consist of pictorial data as well as alphanumeric attributes. The interactive query language allows users to do direct manipulation on the pictorial database because such diagrammatic query formulations represent the users' view of the database schema. Various aspects of OISDBS such as the schema design, storage management, and mapping from semantic schema to relational schema, are also discussed.

Abstract: It is often claimed that strengths of object-oriented approaches include the integration of data and process perspectives, opportunities for reuse and high comprehensibility. In this paper focus is on object-oriented analysis, and the core models of an object-oriented analysis method are examined, formalized and enhanced to define a general framework. Jacobson's method is used as a starting point because of its underlying philosophy and its successful application in practice. Core models are the object-oriented data model and the communication model, which is an integration of the interaction and the behaviour model. As Objectory emphasizes interaction between objects, the paper concentrates on the latter model. The communication model is extended with constructs to specify parallelism within an object, synchronization of concurrent execution paths, and a basic mechanism to receive results from asynchronous service requests.

Abstract: In this paper, we employ the view model given by Bertino to design a secure multi-level object-oriented database system. The central idea is to provide users with multi-level views derived from a single-level secure object-oriented database. The database operations performed on multi-level views are decomposed into a set of operations on single-level objects which can be implemented on any conventional mandatory security kernel. We show that this approach allows us to overcome the difficulties of handling content and context dependent classification, dynamic classification and aggregation and inference problems in multi-level object-oriented databases.

Abstract: In this paper we present a new approach for embedding integrity constraints into object-oriented database systems (OODBS), which can not be specified implicitly by structure or explicitly by keywords of the system. To take those integrity constraints into consideration they have to be integrated into the behavioral part of an object-oriented schema. This paper gives a survey of the existing proposals for this integration and presents a new one, DICE, to overcome the drawbacks of the reviewed solutions. As an example we describe the integration of DICE into object-oriented schema according to ODMG-93.

Abstract: An Integrated Computer-Aided Software Engineering Environment (ICASE) is a software system that can support the development, maintenance, and use of enterprise-wide information resources. An ICASE requires a data model that can represent heterogeneous types of entities and relationships evolving in time and context. This paper describes a data model called FORM (Flexible Object-Relationship Model) for the object management system of ICASEs. FORM is an extended object-oriented data model adopting concepts in semantic data modeling and meta-modeling. Relationship types as well as entity types, both of which can be defined as objects in an object schema help integrate heterogeneous concepts; and meta-types that hold adaptable semantics of object manipulation help raise the automation level of ICASEs. An object-modeling approach for version control is illustrated to show the effectiveness of the framework.

Abstract: The region quadtree is a very popular hierarchical data structure for the representation of binary images (regional data) and it is heavily used at the physical level of many spatial databases. Random sampling algorithms obtain approximate answers of aggregate queries on these databases efficiently. In the present report, we examine how four different sampling methods are applied to specific quadtree implementations (to the most widely used linear implementations). In addition, we examine how two probabilistic models (a parametric model of random images and a model of random trees) can be used for analysing the cost of these methods.

Abstract: In Cyberspace, realized by the Electronic Super-highway and multimedia techniques, persons will be represented by ‘things’ (so called ‘alter-egos’) grown out of the traditional social security numbers. In this paper we will study how the object-oriented methodology can help in designing these inhabitants. By using an interesting example, namely home banking, we will study the problem of security and privacy, in general: access protection, in this world. New in this paper is the combination of Cyberspace, Alter-ego objects representing its inhabitants and protection problems. In particular, we will demonstrate the need for knowledge based capabilities for handling the complex security features which are required in the Cyberspace world.

Abstract: We attempt to determine the rightful roles for natural and formal languages in the development of information systems. In so doing we address three issues. First, we give a set of guidelines for reducing ambiguity in the writing of natural language requirements. Second, we consider domain modeling in terms of patterns defined in natural language, and relate requirements, domain models and formal specifications. Third, we relate domain modeling to our earlier work on queries as a means of constructing conceptual models.

Abstract: Object-oriented data models are being extended with recursion to gain expressive power. This complicates both the incoherence detection problem which has to deal with recursive classes descriptions and the optimization problem which has to deal with recursive queries on complex objects. In this paper, we propose a theoretical framework able to face the above problems. In particular, it is able to validate and automatically classify in a database schema, (recursive) classes, views and queries, organized in an inheritance taxonomy. The framework adopts the odl formalism (an extension of the Description Logics developed in the area of Artificial Intelligence) which is able to express the semantics of complex object data models and to deal with cyclic references at the schema and instance level. It includes subsumption algorithms, which perform automatic placement in a specialization hierarchy of (recursive) views and queries, and incoherence algorithms, which detect incoherent (i.e., always empty) (recursive) classes, views and queries. As different styles of semantics: greatest fixed-point, least fixed-point and descriptive can be adopted to interpret recursive views and queries, first of all we analyze and discuss the choice of one or another of the semantics and, secondly, we give the subsumption and incoherence algorithms for the three different semantics. We show that subsumption computation and incoherence detection appear to be feasible since in almost all practical cases they can be solved in polynomial time algorithms.

Abstract: Rule-based expert system shells have one important drawback in handling uncertain knowledge. It is the drawback that the style of their fuzzy reasoning process and their semantics both are not compatible with those of relational databases. On the other hand, production rule-based languages whose structure is similar to that of the databases fail to possess the fuzzy reasoning ability. Proposed in this paper is a framework to support a semantic based inexact match with Fuzzy Match Predicate (F_MP). In a uniform way it allows matches including fuzzy linguistic variables as well as fuzzy numbers. Our framework also adopts a design alternative to conform not only the semantics of its knowledge representation but also its reasoning style to those of the relational framework. It is a natural consequence that such a design alternative entails a seamless integration of our work into the relational databases. A major advantage of our framework is that it can be implemented on top of the production rule-based languages without modifying their discrimination networks. That is mainly due to the minimal semantic gap between the framework and the languages. In this paper, we demonstrate that: (1) F_MP is a uniform framework to provide the rule-based languages with fuzzy match facilities semantically enhanced, and that (2) its semantic conform well to that of the relational one. We also develop a rule-evaluation mechanism well suited to the aims.

Abstract: In a wireless environment, data objects can be delivered to clients with powerful palmtops in two modes: the broadcasting mode and the on-demand mode. By varying the number of data objects to be broadcast, we can arrive at different scheduling algorithms. Existing work has largely focused on exclusive broadcasting and exclusive on-demand scheduling. In the former, all the data objects are broadcast periodically, while the latter approach provides all data objects on demand. A hybrid approach that partitions air-time between broadcasting popular data objects continuously and providing less frequently accessed data upon request has also been proposed recently. However, none of these techniques performs well in all cases since access to data objects is unpredictable in a highly mobile environment. One of these unpredictable factors is the number of clients. When the number of clients is very large, exclusive broadcasting is the most effective way. On the other hand, when the number of clients is very small, then providing the data objects on demand is superior. Finally, the hybrid strategy turns out to perform well under moderate load provided the appropriate number of data objects is broadcast. In this paper, we propose a dynamic scheduler that is robust to the workload (number of clients). As the workload increases, the scheduler pushes more objects into the air, and as the workload decreases, it pulls objects from the air. We present heuristics for pushing objects into and pulling objects from the air. A simulation study is conducted, and we report on the results in this paper. The results demonstrate the effectiveness and necessity of the dynamic scheduler.