In this paper, we employ the view model given by Bertino to design a secure multi-level object-oriented database system. The central idea is to provide users with multi-level views derived from a single-level secure o...
详细信息
In this paper, we employ the view model given by Bertino to design a secure multi-level object-oriented database system. The central idea is to provide users with multi-level views derived from a single-level secure object-oriented database. The database operations performed on multi-level views are decomposed into a set of operations on single-level objects which can be implemented on any conventional mandatory security kernel. We show that this approach allows us to overcome the difficulties of handling content and context dependent classification, dynamic classification and aggregation and inference problems in multi-level object-oriented databases.
The focus of this article is the transformation of conceptual data models (such as ER, NIAM and PSM) to object-oriented databases. This transformation is captured within the framework of a two-level architecture. Conc...
详细信息
The focus of this article is the transformation of conceptual data models (such as ER, NIAM and PSM) to object-oriented databases. This transformation is captured within the framework of a two-level architecture. Conceptual models are first mapped to abstract intermediate specifications, which are then transformed to database schemas in a given object-oriented database environment. This enables us to treat different target systems in a uniform way. As final implementation environments, we consider object-oriented as well as object-relational DBMSs, including the SQL3 and ODMG-93 standards. We do not reveal the specific details of these standards. Rather, we use intermediate representations expressed in F-logic, a logic-based abstract specification language for object-oriented systems. Several transformation alternatives are discussed in a formal context, resulting in a collection of design options. (C) 1998 Elsevier Science B.V.
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-oriente...
详细信息
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.
The paper gives a brief explanation of the important aspects of object-oriented databases. It summarizes the expected benefits of the application of the object-oriented approach to data manipulation. Two contrasting a...
详细信息
The paper gives a brief explanation of the important aspects of object-oriented databases. It summarizes the expected benefits of the application of the object-oriented approach to data manipulation. Two contrasting approaches to implementation are described. Areas that need investigating to increase the acceptance of object-oriented databases are outlined.
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 obj...
详细信息
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.
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...
详细信息
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. (C) 1999 Elsevier Science B.V. All rights reserved.
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 int...
详细信息
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.
Vertical partitioning is a design technique for reducing the number of disk accesses to execute a given set of queries by minimizing the number of irrelevant instance variables accessed. This is accomplished by groupi...
详细信息
Vertical partitioning is a design technique for reducing the number of disk accesses to execute a given set of queries by minimizing the number of irrelevant instance variables accessed. This is accomplished by grouping the frequently accessed instance variables as vertical class fragments. The complexity of object-oriented database models due to subclass hierarchy and class composition hierarchy complicates the definition and representation of vertical partitioning of the classes, which makes the problem of vertical partitioning in OODBs very challenging. In this paper, we develop a comprehensive analytical cost model for processing of queries on vertically partitioned OODB classes. A set of analytical evaluation results is presented to show the effect of vertical partitioning, and to study the trade-off between the projection ratio versus selectivity factor vis-a-vis sequential versus index access. Furthermore, an empirical experimental prototype supporting vertical class partitioning has been implemented on a commercial OODB tool kit to validate our analytical cost model.
In this paper, we present a set of parameters able to exactly model topologies of object references in object-oriented databases. These parameters are important since they are used to model query execution strategy co...
详细信息
In this paper, we present a set of parameters able to exactly model topologies of object references in object-oriented databases. These parameters are important since they are used to model query execution strategy costs for optimization. The model we present considers also the cases of multivalued attributes and null references. Moreover, a set of derived parameters are introduced and their mathematical derivations are shown. These derived parameters are important, since they allow selectivity of nested predicates to be estimated. Moreover, they are used in estimating storage, access, and update costs for a number of access structures specifically tailored to efficiently support object-oriented queries.
This Paper outlines the use of Prolog for implementing object-oriented databases (OODBs), to indicate both the benefits and costs associated with Prolog as an implementation platform. The different roles which Prolog ...
详细信息
This Paper outlines the use of Prolog for implementing object-oriented databases (OODBs), to indicate both the benefits and costs associated with Prolog as an implementation platform. The different roles which Prolog can play in the implementation of an OODB are illustrated hy reference to example systems which, although they use Prolog as an implementation language, have significantly different architectures. These architectures are compared and assessed, both in terms of the functionality provided to users, and performance.
暂无评论