An object-centered approach for modelling engineering design products: Combining description logic and object-oriented modelling

In this paper we present the Design History Data Model (DHDM), an extended object-oriented data model that explicitly supports the modeling and capture of engineering design histories. An engineering design history is a composite information structure that contains the evolution of engineering design specifications along with the design actions, constraints, and rationale that drove the design process. The capture and classification of engineering design activity is highly beneficial to future designers, assisting in design analysis, design maintenance, design learning, and design reuse. An advantage of the DHDM is that it incorporates a meta data and schema evolution component to support the capture of both pre-specified design activities and dynamic design activities. Pre-specifiable design specifications are those design tasks that are well-known and can be planned in advance of a design activity. Dynamic design involves the specification of design tasks as they actually occur using schema evolution. Modeling design activities is achieved through the use of process classes that are composed of subprocesses through the use of temporal aggregation concepts. Specific occurrences of design activities are modeled as instances of process classes. In addition to introducing the DHDM concepts, this paper describes a prototype implementation of the DHDM on the Itasca object-oriented database system. The prototype DHDM is evaluated with respect to constructibility, comprehensibility, and extensibility of the design history specification.

To deal with issues of data model transformation and to make combined use of different data models, this paper proposed a database reengineering scheme which includes schema translation and data conversion from object-oriented data model to flattened XML data model with is-a and cardinality data semantics preservation. In this paper, conceptual schema of object-oriented data model and flattened XML data model are elaborated by UML class diagram and XML Schema Definition(XSD) graph respectively. Logical schema is described by UNISQL class definition and XSD respectively. This paper firstly analyzes class definitions from OODB and sorts them from most independent classes to most dependent classes. Secondly schema translation is processed by mapping class to complexType and then creating element definitions in XSD file. Thirdly data conversion is processed automatically. Performance tests have shown that the proposed database reengineering scheme is reliable and efficient.

Developing a three-dimensional (3D) data model for Geographic Information Systems (GIS) is an essential and complex issue. 3D modelling in GIS is becoming ever more important for the development of cyber cities and digital earth, which have recently become feasible. A competent 3D model forms an efficient foundation for 3D visualization, query and spatial analysis. As a development of the existing 3D models, this study proposes particular improvements in handling complex 3D objects. We present an object-oriented data model for handling complex 3D objects in GIS. First, the conceptual data model is developed based on the principle of object-oriented (OO) data modelling. This model is designed based on the following three basic geometric elements: node, segment and triangle. Accordingly, the abstract geometric objects are defined: including points, lines, surfaces and volumes. Second, the corresponding 3D logical model is designed based on the defined abstract objects and the relationships between them. Third, a formal representation of the 3D spatial objects is described in detail. Fourth, a prototype 3D GIS is developed based on the proposed 3D data model. Finally, we describe the results of an experimental study to reconstruct 3D objects using this 3D GIS and a comparison with the performance of other 3D data models. The proposed model is able to handle complex objects, such as complex buildings and TV towers, which is an essential functionality for building large-scale cyber cities, such as for Hong Kong. The proposed data model proves to be very efficient, particularly in visualization and rendering. The experimental results show which the data volume of the proposed model is compacted and the visualization speed for 3D objects is improved, compared with the existing models.

A bi-level object-oriented data model together with a user query language called OFQL is designed which can support applications like GIS (geographic information systems). The data model is divided into two layers, the higher-level data model and the lower-level data model. The higher-level data model or the geographic object data model primarily consists of the geographic objects and a set of semantic spatial functions through which the topological relationships of the geographic objects are defined or derived. The lower-level data model or the geometric object data model has geometric objects which are the actual spatial representations of the geographic objects in the higher-level data model. It also has a set of geometric functions that retrieve, manipulate, and compute for geometric objects. The general architecture of a GIS system using this data modeling approach consists of two modules: the query processor and the function implementor. With the OFQL user-interface, the user is able to pose queries of a geographic nature without knowing the details of the spatial representation and computation of the geographic objects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In this paper, we propose a schema versioning mechanism to manage the schema evolution in temporal object-oriented databases. The schema evolution management uses an object-oriented data model that supports temporal features and versions definition – the Temporal Versions Model – TVM. One interesting feature of our proposal is that TVM is used to control not only the schema versioning, but also the storage of extensional database and propagation of the changes performed on the objects. The extensional data level supports integration with the existing database, allowing the maintenance of conventional and temporal versioned objects. The instance propagation approach is proposed through the specification of propagation and conversion functions. These functions assure the correct instance propagation and allow the user to handle all instances consistently in both backward and forward schema versions. Finally, the initial requirements concerning data management in the temporal versioning environment, during schema evolution, are presented.

Using an object-oriented approach to model multimedia data

In the literature there are several proposals to map entity-relationship schemas onto object-oriented schemas, but they only treat relationship sets naÏvely or restrict them to binary relationship sets. We follow a different approach in the treatment of relationship sets. Our goal is to let the designer specify relationships of any arity and then to employ semantic constraints to decompose relationships into smaller fragments. The semantic constraints in use are functional constraints, which are defined in the object-oriented framework. The decomposition process guided by functional constraints is similar to the decomposition process in the relational approach with functional dependencies, but it takes advantage of the features provided by the object-oriented data model. In object-oriented schemas it is possible to enforce a certain kind of functional constraints automatically, namely unary functional constraints.

Two major techniques commonly available for modeling genomic data are the relational and object oriented approaches. This paper discusses the strengths and weaknesses of both approaches. The comparison was done using two sets of disparate genomic data, one for the E. Coli genome and one for the human genome, in order to demonstrate the generality of the modeling methods and the credibility of the comparison itself. One major strength of the object-oriented approach is its highly flexible data modeling power offering an elegant way of representing complex genomic objects. The approach's major weakness includes the lack of generic way of accessing complex objects. The strength of the relational approach is its full provision of SQL. But the approach's weakness is cumbersome modeling of complex genomic objects that is due to normalization. This paper also includes discussions on broader issues related to the two alternative approaches such as support for ad hoc queries and a federation of heterogeneous genomic databases in which both relational and object-oriented data models are used. >

Semantic and object-oriented data models, such as ER, OMT, IFO, and others, have been extensively used for modeling geographic applications. Despite their semantic expressiveness, such models present limitations to adequately model those applications, since they do not provide appropriate primitives for representing spatial data. This paper presents OMT-G, an object oriented data model for geographic applications. OMT-G provides primitives for modeling the geometry and the topology of spatial data, supporting different topological structures, multiple views of objects, and spatial relationships. OMT-G also includes tools to specify transformation processes and presentation alternatives, that allow, among many other possibilities, modeling for multiple representations and multiple presentations. In this way, it overcomes the main limitations of the existing models, thus providing more adequate tools for modeling geographic applications. A comparison with other data models is also presented in order to stress the main advantages of OMT-G.

An object wrapper [3,4] is a piece of middleware that provides an object view on top of a legacy database management system. But legacy database management systems such as relational database systems (RDS) and multidimensional database systems (MDS) [5,6,7] are different in many aspects from an Object-oriented Data Model. Among these aspects are semantic management, data structures and data types supported in these models. As a result, it is crucial to understand these data models in order to design and implement an efficient piece of middleware. In this paper, a short discussion of the real-world data modelling requirements is presented. Then, this is followed by a discussion on an Object View’s requirements. The third section of the paper presents the architecture of the Object-to-Multidimensional Mapping Engine (O-MME) [10,11,12,13,14,15,16,17,18,19]. A detail discussion on major interfaces and classes in the Object-to-Multidimensional mapping algorithm are presented next. Issues such as data type conversion and database language statements generation are discussed in this paper also. Finally, some performance issues are presented and future possible researches are outlined.KeywordsStructure Query LanguageMapping EngineCache ManagerBusiness ClassisRelational Database SystemThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Data schema design as a schema evolution process

Information imprecision and uncertainty exist in many real-world applications, and for this reason fuzzy data modeling has been extensively investigated in various database models. In particular, Zadeh’s fuzzy set theory has been identified as a successful technique for modeling imprecise and uncertain information in various database models. This has resulted in numerous contributions, mainly with respect to the popular fuzzy conceptual data models (fuzzy ER/EER model, fuzzy UML data model, and etc.) and fuzzy logical database models (fuzzy relational database model, fuzzy object-oriented database model, and etc.). Also, it is shown that fuzzy set theory is very useful in Web-based business intelligence. Therefore, topics related to the modeling of fuzzy data are considered very interesting in XML since it is the current standard data representation and exchange format over the Web. In particular, to manage fuzzy XML data, it is necessary to integrate fuzzy XML and various fuzzy databases, and various fuzzy database models (fuzzy relational database model and fuzzy object-oriented database model) need to be used for mapping to and from the fuzzy XML models. Therefore, in this chapter, we mainly introduce several fuzzy database models, including fuzzy UML data model, fuzzy relational database model, and fuzzy object-oriented database model. Before that, we briefly introduce some notions of fuzzy set theory.

Combining Description Logics with synopses for inferring complex knowledge patterns from XML sources

Efficient data warehouse (DW) design depends on the quality of a conceptual model. In this paper, a set of quality metrics have been proposed along with the theoretical validation for quality measurement of conceptual level object-oriented multidimensional data model. The paper also describes the designer level and user level viewpoints of quality evaluation through the criteria like complexity, completeness, expressiveness and analysability. Finally, the work focuses on the empirical validation of the set of metrics and measurements. The empirical validation process shows the usefulness of the proposed metrics for the assessment of operability factor of conceptual level multidimensional data model. Significant correlations exist among the proposed quality measurements and operability factors. The proposed quality evaluation framework is verified in context of a graph semantic-based object-oriented multidimensional data model GOOMD.

It is widely accepted that object-oriented data models are particularly suitable as canonical models for providing data model transparency. In this paper we address issues of reliability of global object identification in global object views arising from requirements for heterogeneity and autonomy. We propose a taxonomy of object identity management policies for providing reliable global OIDs based on (possibly) unreliable local identities. Based on our analysis of the problem domain, we outline a generic object oriented framework for object view implementations that can be refined and configured to the object management needs of a specific data repository. We also argue for the need for some general design guidelines for object views of heterogenous data repositories in which the reliability of local identity plays a major role. >