Susan Darling Urban

Database infrastructure for supporting engineering design histories

Abstract An engineering design history is a step-by-step account of the events and the states through which a design artifact evolved. Database technology has not yet provided adequate mechanisms for capturing and reusing design history information. This paper presents an infrastructure for computer-aided archiving and interrogation of engineering design histories. This framework combines research from software engineering, data engineering, and knowledge engineering to develop an environment for the capture and reuse of design histories. A Design Process Representation Language (DRL), is combined with ‘enhanced’ step models to capture design steps and design parameters. This high-level representation is translated into Data Definition Language (DDL) for operations on an object-oriented database. Advances in database technology that are required to fully support intelligent design history systems are discussed.

Constraint analysis: a design process for specifying operations on objects

A design process for an object-oriented database design environment, known as constraint analysis, is presented. Given the increased level of semantics associated with an object-oriented database schema, constraint analysis makes use of semantics expressed as database constraints to support the flexible specification of propagation actions for operations on objects. Constraints are formally represented using Horn logic. The constraint analysis process then reasons about constraints at design time to help the designer understand the effects of constraints on object manipulation, identifying possible constraint violations as well as design alternatives for handling violations. An advantage of constraint analysis is that both inherent and explicit schema constraints are included in the analysis process. A formal representation is given that supports the analysis of constraints and the automatic identification of design alternatives for responding to constraint violations. >

Refined triggering graphs: a logic-based approach to termination analysis in an active object-oriented database

Presents the notion of refined triggering graphs (RTG) for analyzing termination of active rules in object-oriented databases (OODBs). The RTG method consists of mapping the possibility that one active rule can trigger another to the satisfiability of a well-defined logic formula called a triggering formula. The unsatisfiability of the triggering formula is then an indication that the rule triggering possibility is nil. We identify three increasingly more powerful types of triggering formulae and give pointers to the corresponding satisfiability procedures.

Interconnection of distributed components: an overview of current middleware solutions

From design and manufacturing to electronic commerce, coordinating business activities in engineering applications requires accessing data and software from distributed sources. The Common Object Request Broker Architecture (CORBA) of the Object Management Group emerged in the 1990’s as a standard for access to distributed software components. Since that time, the standard has matured significantly, providing advanced features for event notification and transaction processing. At the same time, Javabased technology for distributed object computing has also emerged, from Remote Method Invocation to Enterprise JavaBeans, Jini Connection Technology, JavaSpaces, Java Messaging Service, and Java Transaction Service. Sorting through the options available for the use of such tools can be a difficult task. This paper provides an overview of CORBA and Java technology for distributed object computing. A comparison of these different technologies is presented, discussing the similarities and differences, as well as the way in which such tools can be used together for distributed access to the types of software and data components that are needed for the construction of distributed engineering applications. Future directions for the use of such tools are also identified.

Development and evaluation of a Web-based signal and speech processing laboratory for distance learning

We describe an Internet-based signal processing laboratory that provides hands-on learning experiences in distributed learning environments. The laboratory is based on an object-oriented Java/sup TM/ tool called Java Digital Signal Processing (J-DSP). J-DSP has been developed at Arizona State University (ASU) and is being used for a virtual laboratory in a senior-level DSP course. J-DSP is written as a platform-independent Java applet that resides on the Web and is thereby accessible by all students through the use of a Web browser. J-DSP has a rich suite of signal processing functions that facilitate interactive on-line simulations of modern statistical signal and spectral analysis algorithms, filter design tools, QMF banks, and state-of-the-art vocoders. J-DSP is accompanied by administrative software tools for secure Internet-based lab-report submission and evaluation including servlets for maintaining Web-based grade books. A series of J-DSP laboratory exercises has been developed and delivered using the ASU distance learning facilities. Student evaluations as well as assessments by experts have been compiled and preliminary results are quite encouraging.

The implementation and evaluation of integrity maintenance rules in an object-oriented database

The authors describe an approach to the declarative representation of integrity constraints in an object-oriented database and the use of integrity maintenance rules for the active maintenance of constraints. A semantic data model is used to automatically generate class definitions and state-altering database operations with constraints represented as objects in the database. Integrity maintenance production rules are automatically generated from constraints and stored as extensions to class operations, hiding the details of constraint checking and rule triggering. High-level transactions call state-altering operations and invoke the integrity maintenance process at commit time. Integrity constraints are declaratively represented in the database system, with operations encapsulating rules about how to respond to constraint violations. An analysis of problems associated with cyclic and anomalous rule behavior.<<ETX>>

Conditional term rewriting as a formal basis for analysis of active database rules

Incorporating active capabilities in an object-oriented database requires a means to guarantee correctness and predictability of active rule behavior. The properties of termination and confluence are particularly important for a wide class of active database applications, including maintaining database consistency upon ad-hoc updates. We model active database rules as conditional term rewrite rules that rewrite the current database state. Rules communicate using messages that represent update requests and occurrences of events. By capturing database dynamics through conditional rewrites, the authors demonstrate the potential of using termination and confluence results developed for conditional term rewrite systems in the analysis of active database rules. These results can serve as a basis for establishing criteria for the development of well-behaved active database applications.<<ETX>>

ALICE: an assertion language for integrity constraint expression

A declarative constraint language, ALICE, for the expression of complex, logic-based constraints in an object-oriented database environment is presented. The translation of ALICE constraints to logic was developed to support a design approach that uses techniques from deductive databases to explain constraints at design time and to specify propagation actions. Two different translations for ALICE constraints are described: one that allows a relaxed interpretation in the presence of null values and one that enforces a stricter interpretation in which the use of null values is limited. An important contribution of ALICE is that the formal, declarative nature of the language forms the basis of a constraint management facility for intelligent object-oriented database environments.<<ETX>>

Synthesis of consolidated data schema for engineering analysis from multiple STEP application protocols

This paper addresses the data modeling aspect of an integrated product data-sharing environment (IPDE) based on the international standard STEP. The IPDE involves multiple design and analysis applications that require data from several STEP Application Protocols (AP203, 209, 214, 224) and integrated resources from different parts of STEP. Issues that were addressed include data granularity, interoperability of STEP-APs, partitioning the APs into units of functionality (UoF), and resolving inter-object references among UoFs. The consolidated data model used for progressive implementation of several prototypes is presented in this paper. Because of limitations of STEP, extensions beyond STEP were necessary for data related to aerodynamic analysis, parametric geometry and constraints. The latter were imported from the ENGEN (ENGEN is a DARPA supported collaborative project managed by PDES, Inc.) Data Model and a new STEP-compliant model was created for CFD. This paper may be regarded as a study of issues related to the synthesis of an integrated data schema from multiple independent topical models.

CONTEXT: a CONstrainT EXplanation Tool

Abstract Encapsulation is an important concept within the object-oriented paradigm. A problem with encapsulation in an object-oriented database, however, is that important semantic information may be hidden within database operations, stripping the database system of information needed for intelligent database activities such as query processing or the ability to reason about objects. This paper describes the functionality of a constraint explanation tool known as CONTEXT. CONTEXT was developed to be used within an environment where database semantics are expressed in a declarative manner, rather than encapsulating constraints within database operations. The database system is therefore responsible for managing information about constraints and checking constraints at execution time. CONTEXT provides a way of sharing information about constraints with the designer at the time database operations are formed, explaining how constraints affect operations and assisting the designer in specifying propagation actions for responding to constraint violations. As a result, operations on objects encapsulate information about how to respond to constraints (in the form of rules), rather than encapsulating information about constraints themselves. The internal processing required to support the explanation of constraints and the identification of alternative propagation actions for transforming constraints to rules is described.