Sandra Heiler

Traversal recursion: a practical approach to supporting recursive applications

Many capabilities that are needed for recursive applications in engineering and project management are not well supported by the usual formulations of recursion. We identify a class of recursions called “traversal recursions” (which model traversals of a directed graph) that have two important properties they can supply the necessary capabilities and efficient processing algorithms have been defined for them. First we present a taxonomy of traversal recursions based on properties of the recursion on graph structure and on unusual types of metadata. This taxonomy is exploited to identify solvable recursions and to select an execution algorithm. We show how graph traversal can sometimes outperform the more general iteration algorithm. Finally we show how a conventional query optimizer architecture can be extended to handle recursive queries and views.

DISTRIBUTED OBJECT MANAGEMENT

Future information processing environments will consist of a vast network of heterogeneous, autonomous, and distributed computing resources, including computers (from mainframe to personal), information-intensive applications, and data (files and databases). A key challenge in this environment is providing capabilities for combining this varied collection of resources into an integrated distributed system, allowing resources to be flexibly combined, and their activities coordinated, to address challenging new information processing requirements. In this paper, we describe the concept of distributed object management, and identify its role in the development of these open, interoperable systems. We identify the key aspects of system architectures supporting distributed object management, and describe specific elements of a distributed object management system being developed at GTE Laboratories.

An Object-Oriented Approach to Data Management: Why Design Databases Need It

An object-oriented approach to management of engineering design data requires object persistence, object-specific rules for concurrency control and recovery, views, complex objects and derived data, and specialized treatment of operations, constraints, relationships and type descriptions. We discuss object-orientation as more than an implementation paradigm, and show how an object-oriented approach simplifies both use and implementation of engineering design systems.

Simplifying complex objects: the PROBE approach to modelling and querying them

Several recent papers have described application requirements, data model capabilities, or implementation approaches for supporting objects with a complex internal structure. These “complex objects” are interesting because they are often found in interesting new applications of databases, such as engineering. Unfortunately, the requirements for complex objects have typically been described without relating them to specific new capabilities required from the DBMS, and frequently the extensions have been tied to the relational model. This paper attempts to clarify the requirements for such capabilities in a model-independent way. It shows that a relatively small number of capabilities are really needed, and outlines how we are trying to incorporate many of them into PROBE, an object-oriented DBMS being developed at CCA.

Querying Part Hierarchies: A Knowledge-Based Approach

Part Hierarchies are a fundamental datatype in CAD applications. But intelligent and efficient processing requires major extensions to DBMS data models, query languages, and processing algorithms. We explore formulations and execution algorithms for path-traversal queries. Hierarchy semantics are then exploited for spatial data and to intelligently choose an appropriate detail level for query output.

EIS/XAIT project: An object-based interoperability framework for heterogeneous systems

Abstract This paper briefly describes various technical issues involved in the design and development of an object-based interoperability framework in support of Engineering Information Systems (EIS). It also discusses the interaction of such frameworks with various emerging standards and the possibility of developing standards in the area of object-oriented interoperable frameworks. Finally, it summarizes the background and the status of the project.

Generating and Manipulating Identifiers for Heterogeneous, Distributed Objects

Systems that manipulate heterogeneous, distributed objects must provide origin-and location-transparent object identifiers. The problem is particularly difficult for systems that deal with “foreign” objects, i.e., objects that originate outside of the system or are manipulated by procedures that are external to the system. Such objects already have externally-assigned identifiers on which clients and application programs depend to access the objects. We describe an approach to providing system-processible identifiers for such objects that preserves the use of their externally-assigned identifiers.