OODINI 2.1 : an enhanced graphical schema representation for object-oriented database

The graphical representation of an object-oriented database (OODB) schema is useful for the designers and users of a database system. The purpose of my thesis was to enhance the existing version of OOdini, an interactive graphical tool for editing an OODB schema. The new features include interactive modification and description of objects in the schema. Data structures for representing classes and attributes have been altered to incorporate object/data types as well as a descriptive string. The software has been implemented using the ObjectMaker toolkit to design our own methodology using the ObjectMaker Extension Language

PolyView : an object-oriented data model for supporting multiple user views

In a typical database application, there are many different users with a great variety of skills, needs and perceptions. The problem of supporting this plethora of user views in a dynamic, data intensive environment is the topic of this dissertation.In traditional record-based systems, all information is represented by an idealized data structure and a set of operations on that structure. User views are defined by simple variations in this structure, such as permuting field names, selecting a subset of the data, or creating links between records. Semantic database models support more complex, "natural" structures. It is often claimed that relativism is supported because semantic schemas can be correctly interpreted (by users) in different ways. The object-oriented paradigm, with its simple and elegant structural semantics, provides both simplicity and richness. Unfortunately, current object-oriented systems only provide a single object interface (or protocol). This dissertation presents PolyView; an object-oriented data model capable of simultaneously supporting many points of view. In PolyView, objects encapsulate a single structure and any number of object interfaces (view instance descriptions). PolyView, therefore, supports distributed mappings from user views to the underlying database structure.Algorithms are presented for generic methods which retrieve and update information through user views. PolyView "colors" queries (messages) by attaching a view identity to them. As messages are propagated through the schema, each receiving object uses the color to determine how the message is to be processed. The color is used to select the user's protocol and allows different user's queries to be processed through apparently different database structures. Because objects act independently, PolyView is a data-driven system; messages are processed without any centralized control or shared memory.Finally, PolyView provides a set of view transformations which allow view administrators to build object interfaces. Since views are supported by both global and localized mechanisms, there are transformations which operate at each of these levels. There are three major categories of transformations presented in this thesis: those which customize the schema as a whole, transformations for changing the structure of the IS-A hierarchy and transformations for customizing attributes

Algorithms for generation of path-methods in object-oriented databases

A path-method is a mechanism in object-oriented databases (OODBs) to retrieve or to update information relevant to one class that is not stored with that class but with some other class. A path-method is a method which traverses from one class through a chain of connections between classes to access information at another class. However, it is a difficult task for a user to write path-methods, because it might require comprehensive knowledge of many classes of the conceptual schema, while a typical user has often incomplete or even inconsistent knowledge of the schema. This dissertation proposes an approach to the generation of path-methods in an OODB to solve this problem. We have developed the Path-Method Generator (P MG) system, which generates path-methods according to a naive user\u27s requests. PMG is based on access weights which reflect the relative frequency of the connections and precomputed access relevance between every pair of classes of the OODB computed from access weights of the connections. We present specific rules for access weight assignment, efficient algorithms to compute access relevance in a single OODB, and a variety of traversal algorithms based on access weights and precomputed access relevance. Experiments with a university environment OODB and a sample of path-methods identify some of these algorithms as very successful in generating most of the desired path-methods. Thus, the PMG system is an efficient tool for aiding the user with the difficult task of querying and updating a large OODB. The path-method generation in an interoperable multi object-oriented database (IM-OODB) is even more difficult than for a single OODB, since a user has to be familiar with several OODBs. We use a hierarchical approach for deriving efficient online algorithms for the computation of access relevance in an IM-OODB, based on precomputed access relevance for each autonomous OODB. In an IM-OODB the access relevance is used as guide in generating path-methods between the classes of different OODBs

A comprehensive part model and graphical schema representation for object-oriented databases

Part-whole modeling plays an important role in the development of database schemata in data-intensive application domains such as manufacturing, design, computer graphics. text document processing, and so on. Object-oriented databases (OODBs) have been targeted for use in such areas. Thus, it is essential that OODBs incorporate a part relationship as one of their modeling primitives. In this dissertation, we present a comprehensive OODB part model which expands the boundaries of OODB part-whole modeling along three fronts. First, it identifies and codifies new semantics for the OODB part relationship. Second, it provides two novel realizations for part relationships and their associated modeling constructs in the context of OODB data models. Third. it, provides an extensive graphical notation for the development of OODB schemata. The heart of the part model is a part relationship that imposes part-whole interaction on the instances of an OODB. The part relationship is divided into four characteristic dimensions: (1) exclusive/shared. (2) cardinality/ordinality, (3) dependency. and (A) value propagation. The latter forms the basis for the definition of derived attributes in a part hierarchy. To demonstrate the viability of our part model, we present two novel realizations for it in the context of existing OODBs. The first realizes the part relationship as an object class and utilizes only a basic set of OODB constructs. The second realization, an implementation of which is described in this dissertation, uses the unique metaclass mechanism of the VODAK Model Language (VML). This implementation shows that our part model can be incorporated into an existing OODB without having to rewrite a substantial subsystem of the OODB, and it also shows that the VML metaclass facility can indeed support extensions in terms of new semantic relationships. To facilitate the creation of part-whole schemata, we introduce an extensive graphical notation for the part relationship and its associated constructs. This notation complements our more general OODB graphical schema representation which includes symbols for classes, attributes. methods. and a variety of relationships. OO-dini, a graphical schema editor that employs our notation and supports conversion of the graphical schema into textual formats, is also discussed