Design of engineering databases: A case for more varied semantic modelling concepts

Interest in database support for engineering applications is rapidly growing. In this paper we concentrate on conceptual database design and address the question of what a semantic model should look like, that meets the needs of engineering applications and is sufficiently formal to support validation, optimization, analysis, as well as transformation to an implementation schema. We present several case studies of engineering databases in order to determine major modelling requirements, and compare these to modelling concepts from the data base and knowledge representation fields. We demonstrate that the main issue is not adding further concepts, but to integrate the existing ones in a selective and precise fashion. We suggest to do so by tailoring the semantic model, starting from a set of base concepts and extending these. An initial model and an extensibility mechanism allowing an explicit and declarative definition of higher-order abstractions are presented. This is demonstrated by specifying some simple concepts such as generalization and a more complex time concept for image sequence evaluation.     

An entity-oriented data model - MIX

Our goal is to make the data in the database more accessible to end-users. We introduce a new data model, called MIX, which incorporates the concepts from semantic data models such as entities, ISA, aggregation, characteristic property, and shared property hierarchies into the universal relation data models (URM) to model a database in a top-down modular way. We then show how a consistent URM style's language can be provided for both database retrievals and database updates. The database schema graph of this model further facilitates us to implement an integrated graphic user interface for the database system design life cycle.     

Modelling data secrecy and integrity

The paper describes a semantic data model used as a design environment for multilevel secure database applications. The proposed technique is built around the concept of security classification constraints (security semantics) and takes into account that security restrictions may either have effects on the static part of a system, on the behavior of the system (the system functions), or on both. As security constraints may influence each other appropriate integrity mechanisms are necessary and modelling of a multilevel application must be data as well as function driven. This functionality is included in the proposed semantic data model for multilevel security by developing secure data schemas, secure function schemas, a procedure for alternating iterative refinements on either schema, and a powerful integrity system to check the consistency of the classification constraints and of the multilevel secure database application.     

Incorporating ontology-based semantics into conceptual modelling

With the increasing complexity of applications and user needs, recent research has shifted from a data-information level to a human semantic level interaction. Research has begun to address the increasing use and development of ontologies in various applications, strongly motivated by the semantic web initiative. However, existing conceptual models are not rich enough to incorporate ontologies in one single conceptual schema. To improve this situation, it is necessary to refine modelling formalisms and make them more expressive while ensuring they remain semantically sound. We argue that conceptual modelling methodologies would be semantically richer if they were able to express the semantics of a domain that arises in concrete application scenarios. This paper investigates the incorporation of ontologies into three popular conceptual modelling methodologies, presenting the Ontological Entity-Relationship (OntoER) model, Ontological Object Role Modelling (OntoORM) and the Ontological Unified Modelling Language (OntoUML) class diagram. An extended conceptual framework for modelling ontologies and a transformation algorithm for mapping ontological constructs to relational schemata are provided so that querying the database through the conceptualisation of the database can be managed.     

Tool support for the design and management of context models

A central task in the development of context-aware applications is the modeling and management of complex context information. In this paper, we present the NexusEditor, which can ease this task by providing a graphical user interface to design schemas for spatial and technical context models, interactively create queries, send them to a server and visualize the results. One main contribution is to show how schema awareness can improve such a tool: The NexusEditor dynamically parses the underlying data model and provides additional syntactic checks, semantic checks, and short-cuts based on the schema information. Furthermore, the tool helps to design new schema definitions based on the existing ones, which is crucial for an iterative and user-centric development of context-aware applications. Finally, it provides interfaces to existing information spaces and visualization tools for spatial data like GoogleEarth.     

一个统计与科学数据库的数据模型

本文提出了一种新的语义数据模型——MICSUM.MICSUM由九种可嵌套引用的语义成分和两个语义成分上的代数操作构成,支持时间序列等复杂数据类型,以统计表和C-关系为数据操作的基本单位,提供了较强的模拟统计与科学数据的能力.     

A Data Manager for Engineering Applications

Efficient data management is crucial to the success of a CAD/CAM system.Traditional databas systems,designed to deal with only regular and structural data,cannot efficiently manage design data.In this paper,we present a data manager called EDBMS/2,which has been developed by our laboratory for engineering support applications.EDBMS/2 has a data model that combines features of both relational and semantic ones and owns flexible abilities for modeling engineering data,such as variable-length data processing,integrated management of structuresd data and unstructured data,and composite object handling.Mechanisms based on DBV and DBV graph concepts,proposed in EDBMS/2 ,make EDBMS/2 own powerful abilities for version management and run efficiently.By now,EDBMS/2 has been used successfully in EDCADS(integrated Electronic Devices CAD environment)project and as a lower level support to develop and object-oriented DBMS for mechanical engineering.     

Database reverse engineering: From the relational to the binary relationship model

This paper describes an algorithmic method for transforming a relational database schema to a binary-relationship one. The source schema may consist of relations that are at any level of normalization, and the designer may add semantic information on the source schema, such as the definition of candidate keys, foreign keys, functional dependencies of various types, multi-valued dependencies, many-to-many constraints, inclusion dependencies, and others. Based on this information, the multi-stage transformation algorithm applies mapping rules to generate object-types, binary-relationships and constraints in the target conceptual schema. The method is implemented as a PC-based tool, utilizing Ingres, SQL and C, and is part of a comprehensive database design tool for both forward and reverse engineering.     

Typology of database quality factors

Databases are a critical element of virtually all conventional and ebusiness applications. How does an organization know if the information derived from the database is any good? To ensure a quality database application, should the emphasis during model development be on the application of quality assurance metrics (designing it right)? A large number of database applications fail or are unusable. A quality process does not necessarily lead to a usable database product. A database application can also be ‘well-formed’ with high data quality but lack semantic or cognitive fidelity (the right design). This paper expands on the growing body of literature in the area of data quality by proposing additions to a hierarchy of database quality dimensions that includes model and behavioral factors in addition to process and data factors.

     

工程数据库管理系统EDBMS的设计与实现

本文从数据管理和工程应用两个方面介绍了一个直接与图形接口管理环境(GIME)、几何造型系统GEMS、交互绘图系统GIS等相联接的面向工程应用的数据库管理系统EDBMS的设计与实现,并讨论了适合于工程应用的系统数据模型、用户接口及其与图形处理系统之间的接口问题.     

Design of statistical databases: A methodology for the conceptual step

The aim of the conceptual step in database design is to describe data involving in the application in a formal and abstract way, without any concern to the specific model and language chosen for the implementation. In statistical applications, data are described at different levels of aggregation, from elementary facts of the reality to complex aggregations such as classifications, time series, indexes. The paper describes a methodology for conceptual design of statistical databases that provides the designer suitable strategies for defining such different levels of aggregation starting from user requirements, and checking the completeness, coherence and minimality of the conceptual schema at the different levels. The methodology makes use of two data models for the representation of data: for elementary data the Entity-Relationship model, widely used in database applications, and for summary data a new model is proposed, designed to be an effective trade-off between expressive power and simplicity of use.     

A semantic framework and software design to enable the transparent integration,reorganization and discovery of natural systems knowledge

I present a conceptualization that attempts to unify diverse representations of natural knowledge while providing a workable computational framework, based on current semantic web theory, for developing, communicating, and running integrated simulation models. The approach is based on a long-standing principle of scientific investigation: the separation of the ontological character of the object of study from the semantics of the observation context, the latter including location in space and time and other observation-related aspects. I will show how current Knowledge Representation theories coupled with the object-oriented paradigm allow an efficient integration through the abstract model of a domain, which relates to the idea of aspect in software engineering. This conceptualization allows us to factor out two fundamental causes of complexity and awkwardness in the representation of knowledge about natural system: (a) the distinction between data and models, both seen here as generic knowledge sources; (b) the multiplicity of states in data sources, handled through the hierarchical composition of independently defined domain objects, each accounting for all states in one well-known observational dimension. This simplification leaves modelers free to work with the bare conceptual bones of the problem, encapsulating complexities connected to data format, and scale. I will then describe the design of a software system that implements the approach, referring to explicit ontologies to unambiguously characterize the semantics of the objects of study, and allowing the independent definition of a global observation context that can be redefined as required. I will briefly discuss applications to multi-scale, multi-paradigm modeling, intelligent database design, and web-based collaboration.     

The application of data types to database semantic integrity

Data type concepts are used to investigate the extent to which database semantic integrity can be defined and ensured through database structures. Database and datatype concepts are extended mutually to improve the semantic capabilities of both database models and data type systems and to resolve apparent discrepencies between databases and programming languages. To meet database needs, data structuring is developed to form an algebra of data types. A semantically rich database model is used to show that database models can be expressed in terms of data types. Finally, a schema specification language is presented to demonstrate the power of data type tools for the definition of database schemas and for the maintenance of database semantic integrity.     

A relational database for non-manipulative representation of solid objects

As the heart of any solid modelling system, much effort has been spent on formulating the data models which represent the shape of a polyhedral solid object within the computer in an accurate, unique and complete manner. Most of this effort has been devoted to make the models manipulateable in terms of computational efficiency, and preserve their semantic integrity. The price paid for achieving these goals is a proliferation of cross-reference data links which, coupled with multiple redundancy, renders the models inefficient for storage or transmission over communication channels. Moreover, the interrogation of these models by non-manipulative applications is usually unsupported functionally, requiring direct accesses to the data, which involves extensive pointer chasing and therefore high familiarity with the manipulative data structure.This paper presents an example relational model as a complementary logical scheme for viewing the shape database that facilitates compact storage and supports non-manipulative query operations through the projection, selection and join operators defined for the relational model, without requiring expert knowledge of the manipulative structure. The flexibility of the relational model, compared with that of the hierarchical, manipulative one, allows easy extensibility and the association of non-geometric attributes with each data item.     

A practical approach to data modelling in spatial applications

The storage and manipulation of spatial data requires a different style of support from that normally found in commercial database systems. This paper explores the use of the functional data model and the high level language Daplex to provide an integrated tool for the conceptual modelling of spatial data and the manipulation of data values. Importance is attached to allowing dynamic schema definition and to the provision of abstract data types to support spatial objects. The implementation comprises three separate modules and uses an underlying relational DBMS to store all metadata and data values. This modular design has enabled the user interface, Daplex language and storage aspects of the software to be developed independently, creating a system which has already proved to be easily portable. Consideration has also been given to ways of improving system performance.     

CAD-integrated engineering-data-management system for spring design

In an iterative design process, a large amount of engineering data needs to be processed. Owing to the limitations of traditional software, the engineering data cannot be handled simultaneously and are usually divided into geometric and non-geometric data in order to be managed by separate systems. In the spring industry, which requires repeated definition of complicated shapes, design engineers need special interfaces for efficient product design and drafting. In this paper, the CAD-integrated engineering-data-management system is developed and implemented for spring design, in order to simplify the drafting and data-management processes. This research focuses on three main issues that can be also applied to other applications, particularly for component designs. These issues include: (1) product model definition, (2) CAD-database communication, and (3) human-machine interface development. With the definition of product model, the system identifies which data should be accessed from data files to generate the proper drawings, and which database structure should be constructed for the application domain. By the use of CAD-database communication, when engineers modify the geometric or non-geometric parameters of a product design, these parametric values can be simultaneously updated in the database. Furthermore, the support of human-machine interface enhances the efficiency in routine manipulation of support engineering data management and design/redesign processes.     

Data structures and DBMS for computer-aided design systems

The structures for the storage of data in CAD systems influence to a large extent the effectiveness of the system. This paper reviews the wide range of data structures and database management systems (DBMS) available for structuring CAD data. Examples of basic data types are drawn from the MODULA-2 language. The relationship between these basic data types, their composite structures and the classical data models (on which many DBMS are based) is discussed, and the limitations of existing DBMS in modelling CAD data highlighted. A set of requirements for CAD database management systems is drawn up and the emerging role of product models (which seek to encapsulate the totality of data elements required to define fully an engineering artefact) is explored.     

Model independent assertions for integration of heterogeneous schemas

Due to the proliferation of database applications, the integration of existing databases into a distributed or federated system is one of the major challenges in responding to enterprises' information requirements. Some proposed integration techniques aim at providing database administrators (DBAs) with a view definition language they can use to build the desired integrated schema. These techniques leave to the DBA the responsibility of appropriately restructuring schema elements from existing local schemas and of solving inter-schema conflicts. This paper investigates theassertion-based approach, in which the DBA's action is limited to pointing out corresponding elements in the schemas and to defining the nature of the correspondence in between. This methodology is capable of: ensuring better integration by taking into account additional semantic information (assertions about links); automatically solving structural conflicts; building the integrated schema without requiring conforming of initial schemas; applying integration rules to a variety of data models; and performing view as well as database integration. This paper presents the basic ideas underlying our approach and focuses on resolution of structural conflicts.