Most common database management systems represent information in a simple record-based format. Semantic modeling provides richer data structuring capabilities for database applications. In particular, research in this area has articulated a number of constructs that provide mechanisms for representing structurally complex interrelations among data typically arising in commercial applications. In general terms, semantic modeling complements work on knowledge representation (in artificial intelligence) and on the new generation of database models based on the object-oriented paradigm of programming languages. This paper presents an in-depth discussion of semantic data modeling. It reviews the philosophical motivations of semantic models, including the need for high-level modeling abstractions and the reduction of semantic overloading of data type constructors. It then provides a tutorial introduction to the primary components of semantic models, which are the explicit representation of objects, attributes of and relationships among objects, type constructors for building complex types, ISA relationships, and derived schema components. Next, a survey of the prominent semantic models in the literature is presented. Further, since a broad area of research has developed around semantic modeling, a number of related topics based on these models are discussed, including data languages, graphical interfaces, theoretical investigations, and physical implementation strategies.

An approach to the coordinated sharing and interchange of computerized information is described emphasizing partial, controlled sharing among autonomous databases. Office information systems provide a particularly appropriate context for this type of information sharing and exchange. A federated database architecture is described in which a collection of independent database systems are united into a loosely coupled federation in order to share and exchange information. A federation consists of components (of which there may be any number) and a single federal dictionary. The components represent individual users, applications, workstations, or other components in an office information system. The federal dictionary is a specialized component that maintains the topology of the federation and oversees the entry of new components. Each component in the federation controls its interactions with other components by means of an export schema and an import schema. The export schema specifies the information that a component will share with other components, while the import schema specifies the nonlocal information that a component wishes to manipulate. The federated architecture provides mechanisms for sharing data, for sharing transactions (via message types) for combining information from several components, and for coordinating activities among autonomous components (via negotiation). A prototype implementation of the federated database mechanism is currently operational on an experimental basis.

Database design commonly assumes, explicitly or implicitly, that instances must belong to classes. This can be termed the assumption of inherent classification. We argue that the extent and complexity of problems in schema integration, schema evolution, and interoperability are, to a large extent, consequences of inherent classification. Furthermore, we make the case that the assumption of inherent classification violates philosophical and cognitive guidelines on classification and is, therefore, inappropriate in view of the role of data modeling in representing knowledge about application domains. As an alternative, we propose a layered appro...

In recent years there has been a growing interest in the explicit introduction of time modelling in a conceptual schema. This has come about as as a result of the relaisation that realisation that the development of large information systems is becoming increasingly more difficult as user requirements become broader and more sophisticated. Arguably the most critical activity in the development of a large data-intensive information system is that of requirements capture and specification. The effectiveness of such a specification depends largely on the ability of the chosen conceptual model to represent the problem domain in such a way so as to permit natural and rigorous descriptions within a methodological framework. The explicit representation of time in a conceptual model plays a major role in achieving this effectiveness. This paper examines the ontology and properties of time in the context of information systems and conceptual modelling. In particular, a critical set of ontologic...

The 3-Dimensional Information Space (3DIS) is an extensible object-oriented framework for infor-mation management. It is specifically oriented toward supporting the database requirements for data-intensive information system applications in which (1) information objects of various levels of abstraction and modalities must be accommodated, (2) descriptive and structural information (metadata) is rich and dynamic, and (3) users who are not database experts must be able to design, manipulate, and evolve databases. In response to these needs, the 3DIS provides an approach in which data and the descriptive information about data are handled uniformly in an extensible framework. The 3DIS provides a simple, geometric, and formal representation of data which forms a basis for understanding, defining, and manipulating databases. Several prototype implementations based upon the 3DIS have been designed and implemented and are in experimental use.

Most of present intelligent knowledge management environments for conceptual modelling and analysis suffer, in our opinion, from mixing two representation levels: (1) a conceptual level, where domain-specific concepts are represented (e.g., data and processes in Data-Flow Diagrams); (2) an epistemological level, where inferences are drawn from domain-independent linguistic constructors (e.g., concepts and roles in Description Logics). We propose an engineering approach to the development of new systems, where the two levels are separately represented and are either linked by the protodl methodology or by concept emulators. We exemplify our approach by modelling Data-Flow Diagrams in level (1) and by using a Description Logic with a Closed Terminology Assumption in level (2). The benefit of the proposed approach lies in decoupling the conceptual level from the underlying epistemological level in the overall architecture of support tools for the construction and the analysis of large dom...

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How can a real-estate agent respond to inquiries quickly and intelligently? The `trick' could be using a simple table to briefly outline the general information and a complete book to reference the details. Such a method can be generalized to the construction of a multiple layered database (MLDB), a useful database organization technique for cooperative query answering, database browsing, query optimization and querying cooperative information systems. In this paper, we study the construction of MLDBs using generalization and knowledge discovery techniques and the application of MLDBs to cooperative/intelligent query answering in database systems. 1 Introduction Cooperative (or intelligent) query answering refers to a mechanism which answers queries cooperatively and intelligently by analyzing the intent of a query and providing some generalized, neighborhood, or associated answers [5, 11, 2]. Many interesting techniques [14, 6, 5, 10, 13, 15] have been developed for cooperative query...

In previous work, we have defined conceptual foundations that can be beneficially used in context modeling. These conceptual foundations include the separation of entity and context, and the characterization of context as either Intrinsic or Relational. This paper aims at extending this approach by introducing the ontological concept of Situation as means of composing the elements of our ontology (entities, intrinsic and relational contexts) to model particular states of affairs of interest. Our concepts have been inspired by and aligned with conceptual theories from the fields of philosophy and cognitive sciences. 1.

Modeling of semantics is one of the most difficult tasks in database design. Constraints are used to express database semantics. They are used differently in database models. They express domain restrictions, specify relationships between components and state database behavior. The utilization depends on the richness of the type system used in the model. The relational model is using a simple type system and has a very large set of integrity constraints. Semantical models are using richer type systems which express also different types of integrity constraints. At the same time, the theory of integrity constraints is more complex. Object-oriented models use either a simple type system or type systems like the semantical models. The theory of integrity constraints is still under development. This overview tries to give a unifying framework on integrity constraints. 1 1 Introduction The goal of this overview is to provide a systematic and unifying introduction to the theory of constrai...