Formal approach for reengineering fuzzy XML in fuzzy object-oriented databases

Since semi-structured documents (e.g., XML) could benefit greatly from database support and more specifically from object-oriented (OO) database management systems, we study the methodology of reengineering XML to object-oriented databases when database migration occurs in this paper. In particular, considering the need of processing the imprecise and uncertain information existing in practical applications, we investigate the problem of migrating fuzzy XML to fuzzy object-oriented databases. To find the object-oriented schema that best describes the existing fuzzy XML schema (DTD), we devise a comprehensive approach centering on a set of mapping rules. Such reengineering practices could not only provide a significant consolidation of the interoperability between fuzzy OO and fuzzy XML modeling techniques, but also develop the practical design methodology for fuzzy OO databases.     

Formal transformation from fuzzy object-oriented databases to fuzzy XML

XML has become the standard for publishing and exchanging data on the Web. Since most of the business data nowadays are stored in structured databases including relational and object-oriented databases (OODB), it is of significance to automate the transformation process and generate the XML data containing information from existing databases. At the same time, information imprecision and uncertainty exist in many practical applications, and for this reason, fuzzy data modeling has been extensively investigated in various data models. As such, there is an increasing need to effectively publish fuzzy structured data as fuzzy XML documents for Web-based applications. In this paper, we take a significant step in a fundamental consolidation of fuzzy XML. In particular, we are interested in finding an XML schema that best describes the existing fuzzy object-oriented schema. To accomplish this, we first offer mapping formalisms to capture the semantics of fuzzy XML Schema and fuzzy object-oriented schema. To allow for better and platform independent sharing of data stored in an object-oriented format, we investigate the formal transformation from fuzzy OODB to fuzzy XML and develop a set of rules to assist in the transformation process.     

Translating update operations from relational to object-oriented databases

In migrating a legacy relational database system to the object-oriented (OO) platform, when database migration completes, application modules are to be migrated, where embedded relational database operations are mapped into their OO correspondents. In this paper we study mapping relational update operations to their OO equivalents, which include UPDATE¹, INSERT and DELETE operations. Relational update operation translation from relational to OO faces the touchy problem of transformation from a value-based relationship model to a reference-based model and maintaining the relational integrity constraints. Moreover, with a relational database where inheritance is expressed as attribute value subset relationship, changing of some attribute values may lead to the change of the position of an object in the class inheritance hierarchy, which we call object migration. Considering all these aspects, algorithms are given mapping relational UPDATE, INSERT and DELETE operations to their OO correspondents. Our work emphasize in examining the differences in the representation of the source schema's semantics resulting from the translation process, as well as differences in the inherent semantics of the two models.     

An object-oriented fuzzy data model for similarity detection in image databases

We introduce a fuzzy set theoretic approach for dealing with uncertainty in images in the context of spatial and topological relations existing among the objects in the image. We propose an object-oriented graph theoretic model for representing an image and this model allows us to assess the similarity between images using the concept of (fuzzy) graph matching. Sufficient flexibility has been provided in the similarity algorithm so that different features of an image may be independently focused upon.     

Conceptual design of fuzzy object-oriented databases using extended entity-relationship model

Entity-relationship–extended entity-relationship models play a crucial role in the conceptual design of relational databases as well as object-oriented databases. Recently, several approaches have been proposed to enhance object-oriented databases (OODBs) using fuzzy set theory. In this paper, we introduce a fuzzy extended entity-relationship model to cope with imperfect as well as complex objects in the real world at a conceptual level. In particular, we provide the formal approach to mapping a fuzzy extended entity-relationship model to a fuzzy object-oriented database schema. © 2001 John Wiley & Sons, Inc.     

Index configuration in object-oriented databases

In relational databases, an attribute of a relation can have only a single primitive value, making it cumbersome to model complex objects. The objectoriented paradigm removes this difficulty by introducing the notion of nested objects, which allows the value of an object atribute to be another object or a set of other objects. This means that a class consists of a set of attributes, and the values of the attributes are objects that belong to other classes; that is, the definition of a class forms a hierarchy of classes. All attributes of the nested classes are nested attributes of the root of the hierarchy. A branch of such hierarchy is called apath. In this article, we address the problem of index configuration for a given path. We first summarize some basic concepts, and introduce the concept of index configuration for a path. Then we present cost formulas to evaluate the costs of the various configurations. Finally, we present the algorithm that determines the optimal configuration, and show its correctness.     

Introduction to object-oriented databases

The object-oriented approach is being used in several areas of computing, including programming, databases, computer-aided design, and office information systems. The paper is a tutorial introduction to object-oriented databases, which is a new application in this field, although object-oriented programming has been under development since the late 1960s. The paper describes the background to object-oriented databases and outlines the rationale for this approach. It concludes with a possible application, in this case a cartographic database, explaining why the object-oriented approach is more appropriate to this application than traditional database approaches, such as the relational approach.     

An interface between object-oriented databases and relational databases

Currently relational databases are widely used, while object-oriented databases are emerging as a new generation of database technology. This paper presents a methodology to provide effective sharing of information in object-oriented databases and relational databases. The object-oriented data model is selected as a common data model to build an integrated view of the diverse databases. An object-oriented query language is used as a standard query language. A method is developed to transform a relational data definition to an equivalent object-oriented data definition and to integrate local data definitions. Two distributed query processing methods are derived. One is for general queries and the other for a special class of restricted queries. Using the methods developed, it is possible to access distributed object-oriented databases and relational databases such that the locations and the structural differences of the databases are transparent to users.     

Inheritance hierarchy design in object-oriented databases

Object-oriented database schema design is still mostly an art. One of the difficulties encountered during design is typing conflicts induced by multiple inheritance. In this paper, we propose a method for treating such a kind of conflicts. Our approach to inheritance conflict solving consists of several ingredients. First, we rely on branding, to introduce ‘type equivalence by name', thus allowing a designer to distinguish between structurally similar but semantically different types. However, we offer a heuristic that does not require a designer to explicitly state branding declarations. Second, we describe various kinds of conflicts, and we offer a set of procedures that analyze a schema to discover such conflicts, classify them, offering potential solutions, if possible. The procedures have been conceived for a design system that allows a designer maximum flexibility, while guiding him/her to a correct design.     

Authorization and revocation in object-oriented databases

Few studies of object-oriented databases deal with their security, a fundamental aspect of systems with complex data structures. Most authorization systems give users who own resources only some basic control over them; here, we provide users with more direct control over their resources by associating with each grant propagation numbers. Propagation numbers govern the grantability and exercisability of the privileges. Of particular interest in our study of authorization in an OO environment is the combination of inheritance and granting of privileges. Diverse policies are discussed and implemented in a test-bed system     

Semantic-based locking technique in object-oriented databases

This paper presents a locking-based concurrency control dealing with three important issues in object-oriented databases: semantics of methods, nested method invocation and referentially shared object. In the proposed scheme, locks are required for the execution of methods instead of atomic operations. This can reduce the locking overhead and deadlocks due to lock escalation. Also, a way of automating commutativity of methods is provided. In addition, concurrency is increased further by use of run-time information. A performance study is conducted by means of simulation using 007 benchmark. Through the simulation, the proposed technique is then compared with the two existing techniques. The performance studies show that the proposed scheme is superior to existing works.     

面向对象在数据库设计中的应用

主要探索一种将面向对象分析应用到数据库系统设计的方法，利用此方法实现一个管理系统。这一方法是把类的整体与部分关系、一般与特殊关系和实例连接应用到数据库设计中。此方法利用了数据库的基本且简单的功能，因而适应性强，可靠性高。     

Approaches to deductive object-oriented databases

The paper is concerned with the problem of combining deductive and object-oriented features to produce a deductive object-oriented database system which is comparable to those currently available under the relational view of data modelling not only in its functionality but also in the techniques employed in its construction and use. Under this assumption, the kinds of issues that have to be tackled for a similar research strategy to produce comparable results are highlighted. The authors motivate their terms of comparison, characterize three broad approaches to deductive object-oriented databases and introduce the notion of language convergence to help in the characterization of some shortcomings that have been perceived in them. Three proposals that have come to light in the past three years are looked into in some detail, in so far as they exemplify some of the positions in the space of choices defined. The main contribution of the paper is towards a characterization of the language convergence property of deductive database languages which has a key role in addressing critiques of the deductive and object-oriented database research enterprise. A basic familiarity with notions from deductive databases and from object-oriented databases is assumed.     

面向对象的数据库设计中的应用

主要探索一种将面向对象分析应用到数据库系统设计的方法，利用此方法实现一个管理系统，这一方法是把类的整体与部分关系，一般与特殊关系和实例连接应用到数据库设计中，此方法利用了数据库的基本且简单的功能，因而适应性强，可靠性高。     

Views as first-class citizens in object-oriented databases

Extensibility and dynamic schema evolution are among the attractive features that lead to the wide acceptance of the object-oriented paradigm. Not knowing all class hierarchy details should not prevent a user from introducing new classes when necessary. Naive or professional users may define new classes either by using class definition constructs or as views. However, improper placement of such classes leads to a flat hierarchy with many things duplicated. To overcome this problem, we automated the process in order to help the user find the most appropriate position with respect to her class in the hierarchy regardless of her knowledge of the hierarchy. The system must be responsible for the proper placement of new classes because only the system has complete knowledge of the details of the class hierarchy, especially in a dynamic environment where changes are very frequent. In other published work, we proved that to define a view it is enough to have the set of objects that qualify to be in a view in addition to having message expressions (possible paths) that lead to desired values within those objects. Here, we go further to map a view that is intended to be persistent into a class. Then we investigate the proper position of that class in the hierarchy. To achieve this, we consider current characteristics of a new class in order to derive its relationship with other existing classes in the hierarchy. Another advantage of the presented model is that views that generate new objects are still updatable simply because we based the creation of new objects on existing identities. In other words, an object participates inside view objects by its identity regardless of which particular values from that object are of interest to the view. Values are reachable via message expressions, not violating encapsulation. This way, actual values are present in only one place and can be updated.Received: 19 March 1999, Accepted: 26 December 2003, Published online: 8 April 2004Edited by: R. Topor.     

Support for modeling relationships in object-oriented databases

Modeling real-world applications typically consists of two parts: the representations of entities of interest, and the representations of relationships among the entities. Object-oriented data models support the first task. This paper argues through examples that the second modeling task is not well supported in current object-oriented database systems. An extended object-oriented data model that facilitates both modeling tasks is developed. This extension provides support for both the representation of complex relationships among entities and their manipulations (queries, updates). A prototype implemented on the ONTOS database management system is briefly described.     

Query execution scheduling in parallel object-oriented databases

Complex object-oriented queries generally consist of path expressions and explicit join operations. Since explicit join operations have been acknowledged as the most expensive operations, query executions normally start from the path expressions. Each path expression may form a sub-query. There are two existing strategies to sub-queries processing: ‘serial’ and ‘parallel’ execution scheduling strategies. Serial sub-queries execution corresponds to an execution of the sub-queries one-by-one, whereas parallel sub-queries execution corresponds to simultaneous execution of the sub-queries. When a sub-query is being processed, parallelization techniques may be applied. In this paper, we focus on the scheduling issues of the sub-queries, rather than the parallelization of the sub-queries themselves. Rules are formulated to guide the parallel query execution process. Our analysis shows that when there is no load skew, the serial scheduling strategy is preferred, otherwise the parallel scheduling strategy should be used.     

System-guided view integration for object-oriented databases

Some of the shortcomings of current view integration methodologies, namely, a low emphasis on full-scale automated systems, a lack of algorithmic specifications of the integration activities, inattention to the design of databases with new properties such as databases for computer-aided design, and insufficient experience with data models with a rich set of type and abstraction mechanisms, are attacked simultaneously. The focus is on design databases for software engineering applications. The approach relies on a semantic model based on structural object-orientation with various features tailored to these applications. The expressiveness of the model is used to take the first steps toward algorithmic solutions, and it is demonstrated how corresponding tools could be embedded methodically within the view integration process and technically within a database design environment. The central ideal is to compute so-called assumption predicates that express suggested similarities between structures in two schemas to be integrated, and then have a human integrator confirm or reject them. The basic method is exemplified for the CERM data model that includes molecular aggregation, generalization, and versioning