A data model, called the entity-relationship model, is proposed. This model incorporates some of the important semantic information about the real world. A special diagrammatic technique is introduced as a tool for database design. An example of database design and description using the model and the diagrammatic technique is given. Some implications for data integrity, infor-mation retrieval, and data manipulation are discussed. The entity-relationship model can be used as a basis for unification of different views of data: t,he network model, the relational model, and the entity set model. Semantic ambiguities in these models are analyzed. Possible ways to derive their views of data from the entity-relationship model are presented. Key Words and Phrases: database design, logical view of data, semantics of data, data models, entity-relationship model, relational model, Data Base Task Group, network model, entity set

. Traditionally, integrity constraints in database systems are maintained either by rolling back any transaction that produces an inconsistent state or by disallowing or modifying operations that may produce an inconsistent state. An alternative approach is to provide automatic "repair " of inconsistent states using production rules. For each constraint, a production rule is used to detect constraint violation and to initiate database operations that restore consistency. We describe an SQL-based language for defining integrity constraints and a framework for translating these constraints into constraint-maintaining production rules. Some parts of the translation are automatic while other parts require user intervention. Based on the semantics of our set-oriented production rules language and under certain assumptions, we prove that at the end of each transaction the rules are guaranteed to produce a state satisfying all defined constraints. We apply our approach to a good-sized example...

SDM is a high-level semantics-based database description and structuring formalism (database model) for databases. This database model is designed to capture more of the meaning of an application environment than is possible with contemporary database models. An SDM specification describes a database in terms of the kinds of entities that exist in the application environment, the classifications and groupings of those entities, and the structural interconnections among them. SDM provides a collection of high-level modeling primitives to capture the semantics of an application environment. By accommodating derived information in a database structural specification, SDM allows the same information to be viewed in several ways; this makes it possible to directly accommodate the variety of needs and processing requirements typically present in database applications. The design of the present SDM is based on our experience in using a preliminary version of it. SDM is designed to enhance the effectiveness and usability of database systems. An SDM database description can serve as a formal specification and documentation tool for a database; it can provide a basis for supporting a variety of powerful user interface facilities, it can serve as a conceptual database model in the database design process; and, it can be used as the database model for a new kind of database management system.

System R is a database management system which provides a high level relational data interface. The system provides a high level of data independence by isolating the end user as much as possible from underlying storage structures. The system permits definition of a variety of relational views on common underlying data. Data control features are provided, including authorization, integrity assertions, triggered transactions, a logging and recovery subsystem, and facilities for maintaining data consistency in a shared-update environment. This paper contains a description of the overall architecture and design of the system. At the present time the system is being implemented and the design evaluated. We emphasize that System R is a vehicle for research in database architecture, and is not planned as a product.

We present an exception handling facility suitable for languages used to implement database-intensive Information Systems. Such a mechanism facilitates the development and maintenance of more flexible software systems by supporting the abstraction of details concerning special or abnormal occurrences. We consider the type constraints imposed by the schema as well as various semantic integrity assertions to be normalcy conditions, and the key contribution of this work is to allow exceptions to these constraints to persist. To achieve this, we propose solutions to a range of problems, including sharing and computing with exceptional information, exception handling by users, the logic of constraints with exceptions, and implementation issues. We also illustrate the use of exception handling in dealing with null values, estimates, and measurements. Keywords and phrases: semantic integrity, violations of type constraints, exception handling, accommodating exceptions, conceptual models CR ...

In this paper, we motivate and present a data model for conceptual design of structural and behavioural aspects of databases. We follow an object centered design paradigm in the spirit of semantic data models. The specification of structural aspects is divided into modelling of object structures and modelling of data types used for describing object properties. The specification of object structures is based on an Extended Entity--Relationship (EER) model. The specification of behavioural aspects is divided into the modelling of admissible database state evolutions by means of temporal integrity constraints and the formulation of database (trans)actions. The central link for integrating these design components is a descriptive logic-- based query language for the EER model. The logic part of this language is the basis for static constraints and descriptive action specifications by means of pre- and postconditions. A temporal extension of this logic is the specification language for tem...

Learning query transformation rules is vital for the success of semantic query optimization in domains where the user cannot provide a comprehensive set of integrity constraints. Finding these rules is a discovery task because of the lack of target. Previous approaches to learning query transformation rules have been based on analyzing past queries. We propose a new approach to learning query transformation rules based on analyzing the existing data in the database. This paper describes a framework and a closure algorithm to learning rules from a given data-distribution. We characterize the correctness, completeness and complexity of the proposed algorithm and provide a detailed example to illustrate the framework. Keywords: Rule discovery, semantic query optimization, discovery in data. Areas Addressed: Learning and Discovery in Database, Data Engineering Tools, Highlevel Query Answering, Applications in Query Optimization. Postal Address 4-192 EE/CS Bldg., 200 Union Stree...

Modern approaches to integrity monitoring suggest to generate triggers from constraints as part of database design and to utilize constraint simplification techniques for trigger optimization. Such proposals, however, have been restricted to static conditions which constrain single states only. In this paper, we show how to derive triggers from dynamic integrity constraints which describe properties of state transitions or state sequences and which can be specified by formulae in temporal logic. Such constraints can equivalently be transformed into transition graphs which describe such life cycles of database objects that are admissible with respect to the constraints: Nodes correspond to situations in life cycles, and edges give the (changing) conditions under which a change into another situation is allowed. If object situations are stored, integrity maintaining triggers can be generated from transition graphs for all situations and all critical database operations. Additionally, new...

Abstract-The workload of an active DBMS consists of two types of activities: externally generated tasks submitted by users, and rule management tasks caused by the triggering of rules stored in the knowledge component of the system. Most design proposals for active DBMS’s assume that an external task should be combined with all the resulting rule management tasks into a single transaction. There is no compelling reason for this assumption, however; the semantics of the rules can be used to divide the workload into transactions in a number of different ways. In this paper, we describe a performance model designed for studying active DBMS performance issues. We present the results of simulation experiments that study system performance as a function of transaction boundary semantics for varying levels of data contention, rule complexity, and data sharing between externally submitted tasks and rule management tasks. Our results demonstrate that the way in which transaction boundaries are imposed can have a major impact on the performance of an active DBMS. We therefore conclude that this aspect of rule semantics must be carefully considered at the time that rules are specified. Index Terms-Active databases, database management, perfor-mance evaluation, rule systems, transaction management. I.

Abstract. The correctness of the data managed by database systems is vital to any application that utilizes data for business, research, and decision-making purposes. To guard databases against erroneous data not reflecting real-world data or business rules, semantic integrity constraints can be specified during database design. Current commercial database management systems provide various means to implement mechanisms to enforce semantic integrity constraints at database run-time. In this paper, we give an overview of the semanticintegrity support in the most recent SQL-standard SQL:1999, and we show to what extent the different concepts and language constructs proposed in this standard can be found in major commercial (object-)relational database management systems. In addition, we discuss general design guidelines that point out how the semanticintegrity features provided by these systems should be utilized in order to implement an effective integrity enforcing subsystem for a database. Keywords: Semanticintegrity constraints – SQL:1999 – Object-relational databases – Constraint enforcement