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OBJECT-ORIENTATION AND THE SQL STANDARD

COMPUTER STANDARDS & INTERFACES 1993年第2-3期15卷 287-300页

作者： KULKARNI, KG TANDEM COMP INC CUPERTINOCA 95014

The database language standard, SQL, adopted by both ANSI and ISO, is now well established as a language for developing database applications. The SQL standard has been evolving ever since its first adoption in 1986, with new revisions being announced every three years. The latest revision (SQL-92) has just been announced by both ANSI and ISO. Currently, work is underway on the next revision, SQL3, which is expected in 1995-96 timeframe. A major focus of SQL3 effort is to incorporate an object-oriented type system while maintaining strict upward compatibility with SQL-92. The type system of SQL3 is based on concepts such as abstract data types, object identity, polymorphism, subtypes-supertypes, parameterized types, dynamic binding, etc. In this paper, we report on the current status of SQL-3 type system.

关键词： ABSTRACT data TYPES ANSI C++ COBOL dataBASE LANGUAGES DYNAMIC BINDING ISO NESTED RELATIONS NON-1ST NORMAL FORM RELATIONS OBJECT IDENTITY MULTIPLE INHERITANCE MULTISETS OBJECT-ORIENTED dataBASE SYSTEMS OVERLOADING PARAMETERIZED TYPES POLYMORPHISM QUERY LANGUAGES RELATIONAL dataBASE SYSTEMS semantic data models SQL SQL-86 SQL-89 SQL-92 SQL3 TYPE TEMPLATES

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A UNIVERSAL RELATION data MODEL WITH semantic ABSTRACTIONS

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IEEE TRANSACTIONS ON KNOWLEDGE AND data ENGINEERING 1992年第1期4卷 23-33页

作者： CHANG, TH SCIORE, E BOSTON COLL DEPT COMP SCICHESTNUT HILLMA 02167

Two important features of modern database models are support for complex data structures and support for high-level data retrieval and update. The first issue has been studied by the development of various semantic data models;the second issue has been studied through universal relation data models. In this paper we examine how the advantages of these two approaches can be combined. We introduce a new data model, which incorporates standard concepts from semantic data models such as entities, aggregations, and ISA hierarchies. We then show how nonnavigational queries and updates can be interpreted in this model. The main contribution of this paper is to demonstrate how universal relation techniques can be extended to a more powerful data model. Moreover, the semantic constructs of our model allow us to eliminate many of the limitations of previous universal relation models.

关键词： ISA HIERARCHIES NONNAVIGATIONAL QUERY PROCESSING semantic data models UNIVERSAL RELATIONS VIEW UPDATES

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SET OPERATIONS IN OBJECT-BASED data models

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IEEE TRANSACTIONS ON KNOWLEDGE AND data ENGINEERING 1992年第4期4卷 382-398页

作者： RUNDENSTEINER, EA BIC, L Department of Information and Computer Science University of California Irvine CA USA

Query languages designed for traditional database systems, such as the relational model, generally support set operations. However, the semantics of these set operations are not adequate for richer data models of newly developed object-based database systems that include object-oriented and semantic data modeling concepts. The reason is that precise semantics of set operations on complex objects require a clear distinction between the dual notions of a set and a type, both of which are present in the class construct found in object-based data models. In fact, class creation by set operations has largely been ignored in the literature. Our paper fills this gap by presenting a framework for executing set theoretic operations on the class construct. The proposed set operations, including set difference, union, intersection and symmetric difference, determine both the type description of the derived class as well as its set membership. For the former, we develop inheritance rules for property characteristics such as single-valued versus multivalued and required versus optional. For the latter, we borrow the object identity concept from data modeling research. Our framework allows for property inheritance among classes that are not necessarily IS-A related.

关键词： COMPLEX OBJECTS CLASS DERIVATION PROPERTY INHERITANCE OBJECT IDENTITY OBJECT-ORIENTED dataBASES SET OPERATIONS semantic data models

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MODELING SECURITY-RELEVANT data semanticS

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IEEE TRANSACTIONS ON SOFTWARE ENGINEERING 1991年第11期17卷 1195-1203页

作者： SMITH, GW National Defense University Information Resources Management College Washington DC 20374

A database system must have knowledge of the semantics (the properties) of the data it manages to accomplish its tasks. For a multilevel secure database system to provide effective multilevel support to users, it must have knowledge of the security-relevant data semantics. Modeling the data semantics of an application domain has been a subject of research for many years in the database community, but these efforts only address integrity properties of data. This paper demonstrates the use of an extended data model which represents both integrity and secrecy aspects of data. This modeling technique can be used as a database design tool and, more importantly, as a vehicle for domain experts, database designers, and security officers to precisely define the security requirements for an application domain. A second contribution is a comprehensive taxonomy of security-relevant data semantics that must be captured and understood to implement a multilevel secure automated information system.

关键词： MULTILEVEL SECURITY dataBASE SECURITY data MODELING semantic data models REQUIREMENTS MODELING INTEGRITY CONSTRAINTS

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FROM semantic data models TO OBJECT ORIENTATION IN DESIGN dataBASES

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INFORMATION AND SOFTWARE TECHNOLOGY 1989年第1期31卷 39-46页

作者： BROWN, AW Dep. Comp. Sci. Univ. York Heslington York YO1 5DD UK

The Aspen project has taken a semantic data model, the extended relational model RM/T, and with the addition of an abstraction mechanism, progressed toward providing an object-oriented database (OODB) as the foundation of an integrated project support environment. In RM/T, a database is considered to consist of a set of entities that represent the objects of interest in the real world; all objects are modeled as entities. These objects of interest can be modeled most effectively by recording them along with the operations that allowed them. Some clear similarities between semantic data models and OODB models are: 1. the use of entity or object identification and support, 2. the obvious importance of relationships between objects, and 3. the support of an object hierarchy with inheritance. The primary differences between the 2 approaches are: 1. a lack of extensibility of the type system in semantic data models, and 2. the purely structured approach to abstraction in semantic data models, contrasted with OODB models' concern for operational behavior as well.

关键词： abstraction model databases IPSE object-oriented databases semantic data models

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COMPLEX PROLOG - A LOGIC dataBASE LANGUAGE FOR HANDLING COMPLEX OBJECTS

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INFORMATION SYSTEMS 1989年第1期14卷 79-87页

作者： GRECO, S RULLO, P CRAI 87036 Rende-Santo Stefano Italy

The logic language paradigm represents a natural extension of relational databases. However, one of its limitations is the lack of suitable data abstraction mechanisms for modeling complex objects. This paper describes Complex-Prolog, a logic database language that provides facilities for data abstraction, notably, the notions of object identity, class and inheritance. This language was designed as an attempt to integrate concepts from logic programming and semantic data models. A formal definition of Complex-Prolog, interspersed with a number of examples, is given. The paper concludes with a description of its implementation.

关键词： Complex objects databases inheritance logic programming semantic data models

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TRADITIONAL, semantic, AND HYPER-semantic APPROACHES TO data MODELING

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COMPUTER 1988年第6期21卷 53-63页

作者： POTTER, WD TRUEBLOOD, RP UNIV GEORGIA CTR ADV COMP METHODSATHENSGA 30602 UNIV S CAROLINA COMP SCICOLUMBIASC 29208

An overview is given of past present data-modeling trends, and future directions are identified. The three traditional and commonly used data models that gained wide acceptance in the late 1960s and early 1970s and are used extensively today, namely the relational, hierarchical, and network models, are reviewed. semantic data models that attempt to enhance the representation of operational information by capturing more of the meaning about data values and relationships are described. Enhancements to semantic data models that characterize hypersemantic data models and emphasize capturing inferential relationships are discussed

关键词： data modeling data structures hierarchical model hypersemantic approaches inferential relationships meaning network models relational model relationships semantic data models

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A FORMAL FRAMEWORK FOR DESCRIBING AND CLASSIFYING semantic data models

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INFORMATION SYSTEMS 1985年第1期10卷 77-96页

作者： STACHOWITZ, RA BURROUGHS CORP AUSTIN RES CTRAUSTINTX 78759

The current lack of a classification system for semantic data models (SDMs) is the result of their dependence on standard predicate calculus, which is limited in expressive power. Consequently, many issues in database Theory cannot adequately be expressed, such as: temporal concepts (before/after insert/update/delete), the triple: true, false, unknown “facts”, existent and non-existent “objects” (null), private and “overlapping” databases with—potentially—conflicting data, i.e. “possible” and “shared” worlds. The classification framework presented is based on systems of logic with greater expressive power than predicate calculus. In these logics, factual, semantic or intensional, modal, and probabilistic statements can be expressed. Two general classification criteria are established: 1. (a) what can be modelled or expressed in the SDM? 2. (b) what can be derived or deduced in the SDM? The descriptive and classificatory apparatus developed provides a satisfactory framework for representing and explaining the topics above and other theoretical issues, such as “open-world assumption” vs “closed-world assumption”, “null-objects” vs “unknown objects”. The individual features are applied to the analysis and comparison of five database models, among them Codd's RM/T and Abrial's binary model. The adequacy of the criteria is further shown by demonstrating that the descriptive features used by Tsichritzis/Lochovsky in data models are contained (as a proper subset) in the framework. The paper concludes with an outlook on inductive systems.

关键词： relational data models semantic data models formal classification criteria semantic classification framework modelling power deductive power predicate calculus manysorted logics intensional logics modal logics entailment logics declarative logics procedural logics meta-language representations model sets model systems null objects unknown objects unknown facts negative facts possible worlds integrity constraints integrity constraint representations

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DEFINING dataBASE DYNAMICS WITH ATTRIBUTE GRAMMARS

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INFORMATION PROCESSING LETTERS 1982年第3期14卷 132-138页

作者： RIDJANOVIC, D BRODIE, ML Department of Computer Science University of Maryland College Park MD 20742 U.S.A.

Because of the increasing complexity and importance of database applications, the pragmatic database community requires precise definitions of database dynamics without the complexity of existing formal methods. semantic data models are introduced to represent static and dynamic properties of database applications in a direct, precise, and abstract way. Thus far, highly mathematically oriented specification techniques of semantic data models have not met with wide acceptance in the database area. The proposed technique has the flexibility to fulfill various precision requirements, but it avoids the complexity of existing formal methods. Context-free grammars are employed to define database statics and, more importantly, attribute grammars are employed to specify database dynamics (integrity constraints).

关键词： semantic data models specification of database integrity constraints context-free and attribute grammars conceptual modelling

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DECOMPILING CODASYL DML INTO RELATIONAL QUERIES

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ACM TRANSACTIONS ON dataBASE SYSTEMS 1982年第1期7卷 1-23页

作者： KATZ, RH WONG, E UNIV CALIF BERKELEY DEPT ELECT ENGN & COMP SCIBERKELEYCA 94720

A decompilation algorithm is developed to transform a program written with the procedural operations of CODASYL DML into one which interacts with a relational system via a nonprocedural query specification. An Access Path Model is introduced to interpret the semantic accesses performed by the program. data flow analysis is used to determine how FIND operations implement semantic accesses. A sequence of these is mapped into a relational query and embedded into the original program. The class of programs for which the algorithm succeeds is characterized.

关键词： decompilation semantic data models

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