Abstract: Changes in requirements for database systems necessitate schema restructuring, database translation, and application or query program conversion. An alternative to the lengthy manual revision process is proposed by offering a set of 15 transformations keyed to the relational model of data and the relational algebra. Motivations, examples, and detailed descriptions are provided.

Abstract: A new schema which models the usage of the logical access paths of the database is proposed. The schema models all database activities (i.e., retrievals and updates), and integrates their logical access paths by recognizing common subpaths and increasing the "weight" of the shared subpaths. The logical access path schema provides a comprehensive picture of the logical access paths, and the cumulative usage of the shared subpaths and/or intermediate results. The schema serves a dual purpose. Firstly, it is used as a model of the access requirements during the database design, and secondly, as the basis for optimization during the operation of the database.

Abstract: This paper describes the design of storage and access structures for a high performance Ada * compatible database management system. This system supports the database application programming language ADAPLEX [Smith81, Smitb82], which is the result of embedding the database sublanguage DAPLEX [Shipman81] in the general purpose language Ada [DoD80]. A prominent feature of the underlying data model is its support for generalization hierarchies [Smith77] which are intended to simplify the mapping from conceptual entities to database objects. An in-depth discussion of the rationale behind our choice of storage and access structures to support semantics intrinsic to the data model and to permit physical database organization tuning is provided in this paper.

Abstract: This paper is concerned with the problem of ensuring the integrity of database systems that are accessed concurrently by a number of independent asychronously running transactions. It is assumed that the database system is partitioned into small units that are referred to as the database entities. The relation between the entities is represented by a directed acyclic graph in which the vertices correspond to the database entities and the arcs correspond to certain access rights. We develop a family of non-two-phase locking protocols for such systems that will be shown to ensure serializability and deadlock-freedom. This family is sufficientdy general to encompass all the previously developed non-two-phase lose locking protocols as well as a number of new protocols. One of these new protocols that seems to be particularly useful is also presented in this paper.

Abstract: We propose a universal relation scheme database model based on the assumption that there is a unique connection among any set of attributes in a relational database. We use the notion of object ([Sc],[MU]) to give a database designer the ability to control how connections in the database are to be made. We show how semantic considerations that follow naturally from the unique connection assumption constrain how objects and the underlying base relations must be syntactically related. We illustrate and motivate our definitions and constraints with several simple examples.

Abstract: In this paper a method for relational database storage organization is presented.The method is based upon a disaggregation of the relations and a subsequent reaggregation to form the domains on which the relations are defined.A hierarchical organization of the domain is proposed in order to keep track of the relational entities (i.e. relations, tuples and attributes) that insist on the values present in the domains.Then we introduce an implementation technique, referred to as Data Pool, suitable to be processed by a database machine capable of "on the fly" track processing.Finally we present an analytic evaluation of the DP method and an example of database and query with performance comparison of the DP method with the most common flat file technique.The proposed method appears to be generally advantageous in storage occupancy; in data retrieval operations it is extremely effective when joins between permanent relations are performed. Good performances can be achieved with other relational operations using proper parallel architectures and, when temporary relations are involved, using special purpose devices.

Abstract: A formal approach is proposed to the definition and the design of conceptual database diagrams to be used as conceptual schemata in a system featuring a multilevel schema architecture, and as an aid for the design of other forms of schemata. We consider E-R (entity-relationship) diagrams, and we introduce a new representation called CAZ-graphs. A rigorous connection is established between these diagrams and some formal constraints used to describe relationships in the framework of the relational data model. These include functional and multivalued dependencies of database relations. The basis for our schemata is a combined representation for two fundamental structures underlying every relation: the first defined by its minimal atomic decompositions, the second by its elementary functional dependencies.The interaction between these two structures is explored, and we show that, jointly, they can represent a wide spectrum of database relationships, of which the well-known one-to-one, one-to-many, and many-to-many associations constitute only a small subset. It is suggested that a main objective in conceptual schema design is to ensure a complete representation of these two structures. A procedure is presented to design schemata which obtain this objective while eliminating redundancy. A simple correspondence between the topological properties of these schemata and the structure of multivalued dependencies of the original relation is established. Various applications are discussed and a number of illustrative examples are given.

Abstract: It is becoming increasingly apparent that we are on the verge ofseveral new technologies that will offer virtually unlimitedsecondary storage at affordable prices Database applicationscan be expected to take advantage of this expanded storagecapacity, and a particularly promising area in this regard isthe use of so-called "non-deletion" or "historical" databasesIt is therefore appropriate to begin exploring formal models f o rthese historical databases -- models that are intrinsicallyoriented toward the storage of data over the course of time, andthat provide a formal semantics for the interaction between timeand the other stored data itemsWe present such a model, the Historical Database Model (HDBM),and define its semantics in terms of an underlying logicalmodel For this purpose we use the language IL-s and its modeltheory, a simplified version of Richard Montague's higher-orderlambda calculus with intensions The HDBM is defined as anextension of the relational database model, incorporating adistinguished STATE attribute that " time-stamps" the factsrecorded in the database Intuitively such a database can beviewed as a set of three-dimensional relations in the ordinary sense The formal semantics is defined in terms of objects (thevalues of keys), which are identified with non-varying orconstant entities, and the properties of these objects (thevalues of non-key attributes), which are identified withindividual concepts is the intensional model Two possibleencodings of the database into the logical model are presentedand discussedIt is a widely accepted view that first-order logic provides aformalization of the semantics of the relational database modelthat has helped to clarify many of the issues in relationaldatabase theory We argue that the richer logic IL-s, with itsbuilt-in notion of "denotation with respect to a moment of timeA¢Â¬Â? and with its capability for naming higher-order objects, is an appropriate vehicle for providing an analogous formal theory of the semantics of an HDB Finally, we briefly discuss our work using IL-s as a target language for interpreting a natural-language query fragment which we have defined as a Montague Grammar, and point to some interesting topics for further research in the general area of time and databases

Abstract: We describe a network schema design algorithm that uses a well-designed relational schema as input. The resulting network database handles incomplete information, since we use only the modified foreign-key constraint and not the universal instance assumption. We believe that the representative instance is a correct representation of information stored in the database. We show how to map the representative instance to the network database. We give two algorithms for translating a relational query to a network application program. The first algorithm is confined to relational queries that express selections and projections over the universal relation scheme. The second algorithm includes all relational queries over select, project and (natural) join. Optimization techniques are discussed for both types of translation.

Abstract: This paper presents and integrates two ideas which can have a long-term impact on the ease of developing interactive computer graphics applications. The first idea is that of using a database management system (DBMS) to manage all the data in an interactive graphics application program (graphical input data, application data, and graphical output data). The second idea is that of replacing much of the traditional procedural specification of an application program with a more concise specification of the dependencies among the input, application, and output data. The underlying system performs the procedures necessary to maintain the dependencies. These two ideas are combined by using a relational DBMS to manage the data, and continuously evaluated qualified updates to specify dependencies to the DBMS. We illustrate these ideas with an example, and discuss the implementation of our system.

Abstract: In an attempt to eliminate motivational inconsistencies, we propose a new approach to relational database theory. Basically, a database schema is treated as a relational view defined over certain atomic, selfexplainable relations, constituting what we call a conceptual schema. In this new framework, we revisit some basic notions of the relational database theory, such as dependencies and schema equivalence. We point out a fundamental difference between functional dependencies, which we treat as constraints over the conceptual schema, and multivalued and join dependencies, which we treat as constraints over the database schema, and which are simply consequences of the way database relations are constructed from conceptual relations. The separation of the database schema from the conceptual schema makes it possible to give a clear definition of a semantics of a database state. It also provides a natural framework to consider equivalence of database schemata.

Abstract: The interconnection between conceptual and external levels of a relational database is made precise in terms of the notion of “interpretation” between first-order languages. This is then used to obtain a methodology for discovering constraints at the external level that are “implied” by constraints at the conceptual level and by conceptual-to-external mappings. It is also seen that these concepts are important in other database issues, namely, automatic program conversion, database design, and compile-time error checking of embedded database languages. Although this the deals exclusively with the relational approach, it also discusses how these ideas can be extended to hierarchical and network databases.

Abstract: The problem of characterizing the number of granules (or blocks) accessed by a transaction is important in modeling the performance of database management systems and other applications. Different expressions for this quantity have appeared in the literature under different probabilistic assumptions. These expressions along with one new result are presented with a uniform notation and a clear statement of the assumptions underlying each. The partial order relating the predictions of the expected number of granules accessed is presented.

Abstract: This paper is intended to introduce those familiar with database management issues to the problems of managing large statistical databases. We begin with a characterization of statistical databases based on the structure and use of the data in the database. Several data management problems are then described. In particular, we discuss the problem of repetitive computations on large segments of the database during the lifetime of a statistical analysis. The organization of a data management system which avoids this problem by caching previously computed results and automatically maintaining their integrity is presented. We conclude with a list of problems that this organization raises and a discussion of related work.

Abstract: It is difficult to imagine a successful semantic theory in which time is not an integral component. In this dissertation we examine the connection between two areas of semantics, namely the semantics of databases and the semantics of natural language, and link them together through a common view of the semantics of time. Part One presents the thesis that an essential ingredient for the success of efforts to incorporate more "real world" semantics into database models is a coherent theory of the semantics of time. We define the historical database model (HDB) as a means of incorporating a temporal semantics within the relational and entity-relationship database models. The HDB model is a very general theory, one which ascribes only the simplest and most intuitive properties to time and defines a simple relationship between time and the other elements of the database model. Part Two presents a formally defined English database query language QE-III, whose semantic theory makes explicit reference to the notion of denotation with respect to a moment of time. This language is defined as a Montague Grammar with a somewhat simplified semantic theory; it offers a natural correspondence to the interpretation of queries in a database context. QE-III is provided with a formal syntax, semantics and pragmatics, each component designed with the database application in mind. This application has motivated several extensions to the traditional conception of a Montague Grammar, extensions that are interesting in their own right: the inclusion of a formal pragmatic component, the inclusion of time-denoting expressions and temporal operators, an analysis of verb meanings into primitive meaning units derived from the database schema, and the inclusion of certain forms of direct questions.

Abstract: This paper outlines an approach to schema acquisition. The approach, called explanatory schema acquisition is applicable in problems solving situations and is heavily knowledge-based. Basically, learning is viewed as a fundamental part of the understanding process. Understanding a situation for which there is no existing schema involves generalizing the new event into a nascent schema. The new schema is then available to aid in future processing and can be further refined via that processing. This approach to learning is unique in several respects: it is not inductive and so is capable of one trial learning, it does not depend on failures to drive the learning process, and it is incremental and learns comparitively slowly. The learning procedure is outlined briefly with an example, a taxonomy of situations involving explanatory schema acquisition is given, and there is a brief discussion on the scope of the learning mechanism.

Abstract: In the past decade, a number of natural language database access systems have been constructed (e.g. Hendrix 1976; Waltz et al. 1976; Sacerdoti 1978; Harris 1979; Lehnert and Shwartz 1982; Shwartz 1982). The level of performance achieved by natural language database access systems varies considerably, with the more robust systems operating within a narrow domain (i.e., content area) and relying heavily on domain-specific knowledge to guide the language understanding process. Transporting a system constructed for one domain into a new domain is extremely resource-intensive because a new set of domain-specific knowledge must be encoded.In order to reduce the cost of transportation, a great deal of current research has focussed on building natural language access systems that are domain-independent. More specifically, these systems attempt to use syntactic knowledge in conjunction with knowledge about the structure of the database as a substitute for conceptual knowledge regarding the database content area. In this paper I examine the issue of whether or not it is possible to build a natural language database access system that achieves an acceptable level of performance without including domain-specific conceptual knowledge.

Abstract: Although a great deal of research effort has been expended in support of natural language (NL) database querying, little effort has gone to NL database update . One reason for this state of affairs is that in NL querying, one can tie nouns and stative verbs in the query to database objects (relation names, attributes and domain values). In many cases this correspondence seems sufficient to interpret NL queries. NL update seems to require database counterparts for active verbs, such as "hire," "schedule" and "enroll," rather than for stative entities. There seem to be no natural candidates to fill this role.We suggest a database counterpart for active verbs, which we call verbgraphs . The verbgraphs may be used to support NL update. A verbgraph is a structure for representing the various database changes that a given verb might describe. In addition to describing the variants of a verb, they may be used to disambiguate the update command. Other possible uses of verbgraphs include, specification of defaults, prompting of the user to guide but not dictate user interaction and enforcing a variety of types of database integrity constraints.

Abstract: In this paper we summarize the research and development in engineering data base management systems by the IPAD project at the Boeing Company.

Abstract: Changing data requirements present database administrators with a difficult problem: the revision of the schema, the translation of the stored database, and the conversion of the numerous application programs. This paper describes an automatic database system conversion facility which provides one approach for coping with this problem. The Pure Definition Language and the Pure Manipulation Language have been designed to facilitate the conversions specified in the Pure Transformation Language. Two conversions and their effect on retrievals are demonstrated.

Abstract: Consider two database schemata modeling the same reality. Given a state of the first schema, we can ask what information it provides about the state of the second schema. It turns out that this information can be represented by a table similar to a tableau of Aho, Sagiv and Ullman. We show a simple method to construct this table, by using results developed for tables of this type in the context of representing incomplete information in relational databases. We also consider a closely related notion of equivalence of database schemata, briefly sketching a method to test two schemata for equivalence.

Abstract: This paper examines three areas where the application of functional dependency theory to relational databases has had an impact. These areas are relational views, database translation and logical database design. The paper refines our earlier work on relational views in which the concepts of consistent and updatable views were proposed. In the area of database translation, it identifies six levels of information preserving relational transformations. Finally, a relational database design algorithm is proposed which combines the best features of the classical synthesis and decomposition approaches while avoiding their identified shortcomings. INTRODUCTION This paper shows, that functional dependency theory provides a unified framework for the analysis of several database problems. The paper represents both a synthesis and extension of our earlier work on each of these problems. The first section contains background infor- mation to familiarize the reader with the terminology and concepts of functional dependency theory. In the second section, functional dependencies are used to define the concepts of consistent and updatable views. Basically, a 'consistent view' is one whose interpretation is consistent with that of the underlying database. An 'updatable view' is one whose updates can be translated into appropriate updates of the underlying database. Together, these definitions describe a class of useable views. In section three, six levels of information preserving relational transformations are identified. These levels reflect the different degrees with which transformations preserve the update and retrieval properties of databases. These levels are important since previously many applications have mistakenly assumed that all the information embodied in their database is preserved by the restructuring operations they have employed. Finally, some shortcomings of the classical synthesis and decomposition approaches to relationship database design are identified in the fourth section. A new algorithm is then proposed which combines the best features of these approaches while avoiding their iden- tified shortcomings.

Abstract: This paper proposes an implementation structure and the corresponding relational model for a building design database. The structure strongly supports designer—database interaction by providing extremely versatile access mechanisms and an associated concurrrency control mechanism. It is demonstrated that the relational model provides a flexibility of access not readily available in other models. The implementation structure supports designer access to database entities by location, attribute value, and combinations of both. It also supports ad hoc groupings of data. At the same time it maintains the integrity of the database against violations caused by concurrent use. Existing concurrency control methods are explored and a new level of locking for concurrency control is proposed. The module is recommended as the optimal level to which a locking mechanism be applied.

Abstract: This paper describes a simulation study of the effect of runtime schema interpretation in a network data model database management system. To perform database operations, programmers use a data manipulation language which supports calls to the data manipulation routines. The data manipulation routines utilize database descriptors from the schema to determine which operations on the database are to be performed for a given actual parameter to the procedure. Current database systems perform the binding of schema descriptors in the data manipulation routines at run-time by interpretation. A niumber of researchers are studying methods to precompute the information required to determine the correct function to execute rather than using run-time interpretation.