Browsing by Author "Ling T W"

Now showing 1 - 7 of 7
  • No Thumbnail Available
    Item
    Extending Classical Functional Dependencies for Phsical Database Design
    (1994-05-01T00:00:00Z) Ling T W; Goh C H; Lee M L
    Traditionally, database design activities are partitioned into distinct phases in which a logical design phase precedes physical database design. The objective of the logical design step is to eliminate redundancies and updating anomalies using the notion of data dependencies, while leaving the physical design step to consider how the database schema may be restructured to provide more efficient access. We argue in this paper that the separation of these two steps often result in physical database design not being able to benefit from knowledge of the semantics of data captured in the earlier phases of the database design life cycle. As a step towards overcoming this problem, we demonstrate how classical functional dependencies can be extended to capture data semantics relevant to the design of database schemas which are more desirable from the efficiency point of view. This is accomplished via the introduction of strong and weak functional dependencies, as well as three new formal forms --- the relaxed 3NF, replicated 3NF and relax-replicated 3NF --- induced by the extended functional dependencies. These new normal forms provide a framework for designing database schemas which are more efficient, while not compromising the integrity of the underlying database.
  • No Thumbnail Available
    Item
    Generating Object-Oriented Views from an ER-Based Conceptual Schema
    (1992-08-01T00:00:00Z) Ling T W; Teo P K; Yan L L
    Abstract not available.
  • No Thumbnail Available
    Item
    A Normal Form Object-Oriented Entity Relationship Diagram
    (1994-06-01T00:00:00Z) Ling T W; Teo Pit Koon
    A normal form object-oriented entity relationship (OOER) diagram is presented to address a set of OO data modelling issues. These issues include the inability to judge the quality of an OO schema, the presence of inheritance conflicts in ISA hierarchies, the lack of explicit support for different relationship types (m-n, n-ary, recursive etc.) in some OO data models and the lack of general and flexible support for views. Three approaches are described to translate good quality OO schemas from a normal form OOER diagram. The first approach translates OO schemas whose underlying OO data models support the notion of relationship. There are no undesirable redundancies in the translated schemas. The second approach provides for OO data models that do not support the notion of relationship. Some redundancies may arise because of m-n, n-ary relationships, but these can be controlled. The third approach treats each OO schema as an external schema of a conceptual schema represented by a normal form OOER diagram. Redundancies may exist at the external schema level, but no redundancies exist at the conceptual schema level.
  • No Thumbnail Available
    Item
    On Conflicts in Class Hierarchies of Object-Oriented Systems
    (1992-04-01T00:00:00Z) Ling T W; Teo P K
    Abstract not available.
  • No Thumbnail Available
    Item
    Toward Resolving Inadequacies in Object-Oriented Data Models
    (1993-03-01T00:00:00Z) Ling T W; Teo P W
    Abstract not available.
  • No Thumbnail Available
    Item
    Towards a Synergistic Integration of the ER and Relational Formalisms for Logical Database Design
    (1992-03-01T00:00:00Z) Ling T W; Goh C H
    Abstract not available.
  • No Thumbnail Available
    Item
    View Update in Entity-Relationship Based Database Management Systems
    (1992-02-01T00:00:00Z) Ling T W; Lee M L
    Abstract not available.