Pre-physical data base design heuristics

Data base design encompasses both business and technical aspects. Conceptual data modelling creates a conceptual schema to abstract the user view of data within the business context. This conceptual schema is mapped to the logical data model structure in order to obtain a set of normalized relations. These ensure the integrity of the data by avoiding update anomalies. Regardless of the methodology used, the process or transaction model will impact on the data base design process and its refinement. Since the process or transaction model will reflect the business requirements and specific users view of the data, it will determine the relevance of having a fully normalized set of data, or the need for trading off some degree of normalization, with the aim of improving performance in the query process. The model will also indicate the activity requirements on the relations in the logical data model, their frequency, and characteristics. A pre-physical design step is described, and a set of heuristics is proposed in order to obtain a refined data base design.     

Treating data privacy in distributed systems

This papers describes and is primarily concerned with the security data definition and management in a distributed data base of aggregated type, although the approach described may be applied to any distributed system architecture. A multi-level logical security architecture is presented reflecting the logical architecture of the distributed system. In particular, three security logical schemata are proposed: the network security schema, the external security schemata, and the intermediate security schemata. For each schema data models are introduced, allowing the definition and the management of security information. Mapping rules between the logical levels are discussed. Finally security mechanisms are analyzed.     

Data base design constrained by traffic load estimates

This paper discusses a mathematical model for finding an effective design of a logical data base. It is argued that a logical data base should not only integrate multiple users' views of information. It should also reflect the data base activity of each individual application and be based on performance tradeoffs among the different applications. Our model shows how this activity can be mapped into activity within the global information structure which describes the integrated view of the information. This is an aid for subsequent logical record definition and schema design.

The model is based on knowledge of a large number of input parameters, some of which have greater impact on the final data base solution than others. Sensitivity analysis of the system's behaviour with respect to changes in parameters help focus on the most critical parameters. This reduces the efforts devoted to quantification of parameters, so that default values or very rough estimates are sufficient for the least critical parameters.     

Semantic and pragmatic processing in FIDO: A flexible interface for data-base operations

This article deals with a flexible natural language interface to access data stored in a relational data base. This interface may prove of great value to the less sophisticated user.The FIDO system (Flexible Interface for Database Operations) is presented; it accepts queries issued in natural language (Italian) and translates them into relational algebra operations. FIDO is composed of a parser (not described in the paper), a two-level semantic network, which (among other things) expresses the correspondence between the natural language terms and the conceptual database objects, and a translator/optimizer, which translates the conceptual query into its logical equivalent (i.e. into a query expressed in terms of stored relations and their attributes). The article describes the main characteristics of the semantic network and addresses, in greater detail, the problem of query translation and optimization.The flexibility of FIDO is due to the complete independence of the semantic knowledge source from the logical schema of the data base. In fact, the logical schema can be designed on the basis of considerations not related to the overall structure of FIDO (e.g. the presence of particular types of applications that have to be implemented in a particularly efficient way). In principle, the (relational) data base could be preexistent with respect to the adoption of FIDO, in that the data structures used by the translator/optimizer and described in this paper are able to describe the correspondence between the conceptual model of the domain and different logical schemas.     

Data base communication in a heterogeneous data base management system network

An architectural approach is outlined toward the long range goal of a far-reaching data base communication system capable of supporting a network in which any user in any network node can be given an integrated and tailored view or schema (e.g. hierarchical, relational), while in reality the data may reside in one single data base or in physically separated data bases, managed individually by the same type of GDBMS (e.g. CODASYL, IMS, relational) or by different GDBMS. A series of data base model layers and mappings or translations between these layers are proposed. The entity-relationships model is fundamentally used for the highly logical model layers of the integrated system and a modified DIAM is used for the physical distribution and access path oriented layers. A comprehensive example of an integrated network of heterogeneous data bases is outlined, showing for a set of queries their formulation through different layers of the system from the virtual user realm to the physical data bases. Major challenges and issues are discussed.     

Navigational facilities for relational data base

Charles Bachman's great idea of navigation in a data base is applied to the relational data model. This idea, understood as a way of user thinking, is formulated in such a manner, that no physical concepts are introduced to the user's awareness. Thus the demanded level of data independence is not reduced.A concept of “navigational statement” is defined. The navigational statements may be used to improve other relational languages, for example SEQUEL. It is shown that navigational statements simplify the grammar structure of language expressions and make them shorter and more readable. Elliptic (incomplete) navigational statements are also defined. Such statements may be regarded as a good tool for the casual user.This paper may be viewed as a (not necessarily complete) review of possibilities related to the idea of navigation in a relational data base.     

The Logical Access Path Schema of a Database

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.     

A model-driven approach to semi-structured database design

Recently XML has become a standard for data representation and the preferred method of encoding structured data for exchange over the Internet. Moreover it is frequently used as a logical format to store structured and semi-structured data in databases. We propose a model-driven and configurable approach for modeling hierarchical XML data using object role modeling (ORM) as a flat conceptual model. First a non-hierarchical conceptual schema of the problem domain is built using ORM and then different hierarchical views of the conceptual schema or parts of it are specified by the designer using transformation rules. A hierarchical modeling notation called H-ORM is proposed to show these hierarchical views and model more complex semi-structured data constructs and constraints. We also propose an algorithm to map hierarchical H-ORM views to XML schema language.     

星链ER模型:一种数据仓库概念设计模型

对于流程工业中的数据仓库建设，存在一贯性质量分析的需求，即前一个工序的工艺可能影响下一个工序的产品质量．针对这种需求，提出了一种数据仓库的概念设计模型，星链ER模型．其中引入了链式事实主题结构的概念，并把度量细分为传递型度量与非传递型度量，给出了星链ER模型的图形表示法以及由概念模型到逻辑模型的转换规则．该模型可以方便地转化成多种逻辑模型如星型模式、雪花模式以及星座模式．     

On the equivalence of data base schemas—a semantic approach to data translation

A notion of the equivalence of data is the basis for deriving a correct translation of data bases. The equivalence of data base states and data base schemas is defined. Since this definition can only be given with respect to the semantics of data, a short discussion of data base semantics is given. It is shown, how a semantic data model and data definition language (LDDL) can be used to construct a correct specification of a translation function. Finally, an example of the translation of a CODASYL data base schema to a relational data base schema is given.     

The XML Tree Model – toward an XML conceptual schema reversed from XML Schema Definition

XML Schema Definition (XSD) is the logical schemas of an XML model, but there is no standard format for the conceptual schema of an XML model. Therefore, we propose an XML Tree Model (XTM) as an XML conceptual schema for representing data semantics in a diagram, and also as an XML data model validator for confirming the data semantics required by users. An XTM consists of hierarchical nodes representing all the elements, and the data relationships among elements within the XSD. A rule-based algorithm and an information capacity with pre- and post-conditions are developed as the methodology for reverse engineering. The proposed algorithm consists of two rules: General Information Transformation and Data Semantic Recovering to construct an XTM. Users can draw an XTM with data relationships among elements as a result of the reverse engineering.     

Logical data base design: A management-oriented approach

A logical data base consists of data definitions and data relationships. It is typically very large and complex even for a small organization, but it is generally designed in an ad hoc manner. However, several approaches have recently been proposed that allow for a systematic logical data base design.To make a data base more useful to the managers, it is imperative to encourage and obtain their involvement in the initial phase of the logical data base design. “Surface semantic models” are used in the logical data base design process to increase this involvement. A special type of this, called a “hierarchical external view model”, is proposed. It has been successfully used to develop a logical data base for the Department of Aging in Pennsylvania.     

CAD^2B—一个计算机辅助数据库设计系统

本文介绍了一个用Ｔｕｒｂｏ Ｃ语言在ＡＳＴ－２８６机器上实现的计算机辅助数据库设计系统ＣＡＤ＾２Ｂ。该系统提供了人机交互的环境，供设计者进行概念模型设计，并自动完成从概念模型逻辑模型的映射，创建满足规范化要求的关系表。该系统采用的概念模型是引入了事件和时间的扩展了的实体关系模型。该模型既能充分反映应用环境的静态和动态语义，又是向关系模式转化的基础。     

A conceptual schema-based temporal meta database schemas generation technique for 3D objects

In this paper, a temporal meta database for three-dimensional (3D) objects whose properties and relationships are supported by valid time is introduced. Based on our proposed temporal object-oriented conceptual schema model, a conceptual schema of the temporal meta database can be generated from a 3D graphical data source and other particular application requirements. Based on our proposed temporal object relational data model with attribute timestamping, logical schemas of the temporal meta database can be systematically and automatically generated from the conceptual schema. From the temporal meta database, non-temporal/temporal metadata about temporal 3D objects are available for temporal information system users. Convenient access using database languages such as SQL can be performed. Queries over 3D objects using a temporal object relational SQL are demonstrated.     

Translating relational schema into XML schema definition with data semantic preservation and XSD graph

Many legacy systems have been created by using relational database operating not for the Internet expression. Since the relational database is not an efficient way for data explosion, electronic transfer of data, and electronic business on the Web, we introduce a methodology in which a relational schema will be translated to an Extensible Markup Language (XML) schema definition for creating an XML database that is a simple and efficient format on the Web. We apply the Indirect Schema Translation Method that is a semantic-based methodology in this project. The mechanism is that the Relational Schema will be translated into the conceptual model, an Extended Entity Relationship (EER) Model using Reverse Engineering. Afterward, the EER model will be mapped to an XML Schema Definition Language (XSD) Graph as an XML conceptual schema using Semantic Transformation. Finally, the XSD Graph will be mapped into the XSD as an XML logical schema in the process of Forward Engineering, and the data semantics of participation, cardinality, generalization, aggregation, categorization, N-ary and U-ary relationship are preserved in the translated XML schema definition.     

MEER—An EER model enhanced with structure methods

Entity relationship (ER) schemas include cardinality constraints, that restrict the dependencies among entities within a relationship type. The cardinality constraints have direct impact on the application maintenance, since insertions or deletions of entities or relationships might affect related entities. Indeed, maintenance of a system or of a database can be strengthened to enforce consistency with respect to the cardinality constraints in a schema. Yet, once an ER schema is translated into a logical database schema, or translated within a system, the direct correlation between the cardinality constraints and maintenance transactions is lost, since the components of the ER schema might be decomposed among those of the logical database schema or the target system.In this paper, a full solution to the enforcement of cardinality constraints in EER schemas is given. We extend the enhanced ER (EER) data model with structure-based update methods that are fully defined by the cardinality constraints. The structure methods are provably terminating and cardinality faithful, i.e., they do not insert new inconsistencies and can only decrease existing ones. A refined approach towards measuring the cardinality consistency of a database is introduced. The contribution of this paper is in the automatic creation of update methods, and in building the formal basis for proving their correctness.     

基于依存语法构建多视图汉语树库

树库是自然语言处理中一项重要的基础资源,现有树库基本上都是单视图树,支持短语结构语法或者依存语法。该文提出一套基于依存语法的多视图汉语树库标注体系,仅需标注中心语和语法角色两类信息,之后可以自动地推导出描述句法结构所需的短语结构功能和层次信息,从而可以在不增加标注工作量的前提下获得更多语法信息。基于该体系,构建了北京大学多视图汉语树库(PMT)1.0版,含有64000句、140万词,支持短语结构语法和依存语法两个视图。     

图文法遗传算法

本文讨论了进化神经网络的编码表示机制，分析了它们的优缺点；提出了遗传算法的一种图文法编码表示机制，给出了相应的算子定义，以及模式、模式长度及其阶的定义；证明了一个基于图文法表示机制的遗传算法模式定理，描述了交叉和突变对模式作用的效果。