The paper describes a novel method for creating views in an object-oriented database system by using a mechanism termed 'dynamic instance conversion'. In this system, views are not defined as the result of a q...
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The paper describes a novel method for creating views in an object-oriented database system by using a mechanism termed 'dynamic instance conversion'. In this system, views are not defined as the result of a query expression but rather by reference to the class of which a view is to be made. It is argued that this approach is better suited to OODBs than the use of query expressions as it is more in keeping with the object-oriented paradigm. Instances of a class are automatically converted between views to appear in the format demanded by a query. This happens without loss of information by the instances, thus ensuring that changes to a view are 'updated' correctly. A Graphical User Interface (GUI) to the view system is also described. This GUI facilitates the creation of views and provides support for the definition of methods used to update view changes.
In order to deal with a physical quantity which generally consists of a number and a unit expression, the nature of the unit expression is analysed with regard to: (1) the syntax of the unit expression, (2) the struct...
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In order to deal with a physical quantity which generally consists of a number and a unit expression, the nature of the unit expression is analysed with regard to: (1) the syntax of the unit expression, (2) the structure of the unit expression space, (3) the mapping between the unit expression space and the physical quantity space. The proposed system accepts the physical quantity literal and returns its magnitude and corresponding physical quantity with the help of a unit and prefix database taking into account unit conversion. To map an arbitrary physical quantity literal to the appropriate quantity and also to evaluate its magnitude, the system exploits the dimension born in every legitimate unit expression and the unique correspondence between the physical quantity and the dimension. A general method to provide a consistent unit database is proposed. This system will be valuable as a front-end of a database system in reducing users load in inputing and viewing many and a variety of physical quantities and in keeping the contents of the database consistent.
In this paper, we present methods of translating transactions from object-oriented database (OODB) to relational database (RDB). The process involves schema mapping in data definition language and transaction translat...
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In this paper, we present methods of translating transactions from object-oriented database (OODB) to relational database (RDB). The process involves schema mapping in data definition language and transaction translation in data manipulation language. They include scheme definition, data query and transaction operation of insert, update, and deletion. We also discuss the object-oriented features in OODB operations that are not supported by RDB, such as class hierarchy, class composition hierarchy, and set attribute, and provide a general solution to realize those mechanisms by traditional relation operations. The result of the transaction translation can be applied into adding object-oriented interface into relational database management system and to the interoperability between OODB and RDB. (C) 2002 Elsevier Science B.V. All rights reserved.
InterSect is a prototype hypertext system designed to meet the requirements of complex documentation environments. It differs from conventional hypertext systems in that its nodes can behave like records in a database...
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InterSect is a prototype hypertext system designed to meet the requirements of complex documentation environments. It differs from conventional hypertext systems in that its nodes can behave like records in a database, as well as participating in normal hypertext links. This helps to overcome some of the problems, such as getting lost in hyperspace, exhibited by first-generation hypertext systems. The object-oriented database DAMOKLES is used in the prototype. The paper describes the use of the formal language Z to specify the InterSect system.
Departing from pure Datalog and simple constraints arising from the logical objects, a underling theory can be obtained which permits to study certain aspects of optimization. A logical access language for objects, ca...
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Departing from pure Datalog and simple constraints arising from the logical objects, a underling theory can be obtained which permits to study certain aspects of optimization. A logical access language for objects, called U-LOG 3, has been conceived and implemented along these lines. U-LOG 3 can performed two kinds of optimization: a symbolic optimization and an optimization of physical access to objects. The first one is performed through a confluent rewriting system and which consists upon the reduction of the sorts involved in the logical objects, exploiting the information contained in the signature. In this paper, we briefly discuss U-Log 3 underlying theory and symbolic optimization, after motivating our switch from feature logic to Datalog + Constraints. (C) 1997 Published by Elsevier Science Ltd.
Method invocation mechanism is one of the essential features in object-oriented programming languages. This mechanism contributes to data encapsulation and code reuse, but there is a risk of runtime type errors. In th...
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Method invocation mechanism is one of the essential features in object-oriented programming languages. This mechanism contributes to data encapsulation and code reuse, but there is a risk of runtime type errors. In the case of object-oriented databases (OODBs), a runtime error causes rollback. Therefore, it is desirable to ensure that a given OODB schema is consistent, i.e., no runtime error occurs during the execution of queries under any database instance of the OODB schema. This paper discusses the computational complexity of the type-consistency problem. As a model of OODB schemas, we adopt update schemas introduced by Hull et al., which have ail of the basic features of OODBs such as class hierarchy, inheritance, complex objects, and so on. The type-consistency problem for update schemas is known to be undecidable. We introduce a subclass of update schemas, called acyclic schemas, and show that the type-consistency problem for acyclic schemas is in coNEXPTIME. Furthermore, we show that the problem for recursion-free acyclic schemas is coNEXPTIME-hard and the problem For retrieval acyclic schemas is PSPACE-complete.
A locking model adopting a multi-granularity approach is proposed for concurrency control in object-oriented database systems. The model is motivated by a desire to provide high concurrency and low locking overhead in...
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A locking model adopting a multi-granularity approach is proposed for concurrency control in object-oriented database systems. The model is motivated by a desire to provide high concurrency and low locking overhead in accessing objects. Locking in schemas and locking in instances are developed separately and then are integrated. Schema changes and composite objects are also taken into account. A dual queue scheme for efficient scheduling of lock requests is developed. The model consists of a rich set of lock modes, a compatibility matrix, and a locking protocol. Characteristic query examples on single class, class lattice, and composite objects are used to illustrate the comparison between the ORION model and the proposed model. It is shown that our locking model has indeed made some improvements and is suitable for concurrency control in object-oriented databases.
This paper presents a practical concurrency control mechanism - objectLockingin OODBMS. object-Locking can schedule transactions, each of themcan be considered as a sequence of high level operations defined on classe...
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This paper presents a practical concurrency control mechanism - objectLockingin OODBMS. object-Locking can schedule transactions, each of themcan be considered as a sequence of high level operations defined on classes. Bythe properties of parallelity and coatativity between high level operations,proper lock modes for each operation are desigued and the compatibility matrixis constructed. With these lock modes, phatoms are kept away from databasesand a high degree of concurrency is achieved.
Authorization is an important functionality that every data management system should provide. An authorization mechanism allows different access rights on data items to be selectively assigned to users. Authorization ...
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Authorization is an important functionality that every data management system should provide. An authorization mechanism allows different access rights on data items to be selectively assigned to users. Authorization models and mechanisms have been widely investigated in the framework of traditional database systems. The extension of those models and mechanisms to advanced data management systems is quite complex, because those systems are characterized by data models with a larger number of semantic constructs than traditional models, like the relational one. A first authorization model defined for object-oriented (and semantic) database systems has been presented in [20]. In this paper we present an authorization model that substantially extends and revises that model. The most significant extension concerns the support for content-dependent authorization, which was not provided in [20]. Content-dependent authorization is very important in providing an authorization mechanism able to directly support authorization policies of application environments. Moreover, it is a crucial functionality in environments where data objects frequently change their status. In addition, the model presented here differs from the model defined in [20] in that new authorization types are introduced and a finer control of versions is provided. Finally, authorization administration of objects is considered.
The rapid development of the Internet promotes that XML is increasingly accepted as a medium for integrating and exchanging data. Meanwhile, object-oriented database with many excellent properties has been applied mor...
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The rapid development of the Internet promotes that XML is increasingly accepted as a medium for integrating and exchanging data. Meanwhile, object-oriented database with many excellent properties has been applied more and more widely. In particular, considering the need of processing the fuzzy spatiotemporal data existing in practical applications, we study the methodology of building fuzzy spatiotemporal data model and transforming fuzzy spatiotemporal data from XML to object-oriented database as well. To establish a suitable model, we devise a fuzzy spatiotemporal data model in XML to capture the semantics of fuzzy spatiotemporal features. In addition, we take the object-oriented schema that best describes the exciting fuzzy XML Schema and the characteristics of the XML tree structure into account to develop a series of rules to map spatiotemporal data from XML to object-oriented database. Such mapping rules could provide a significant consolidation of the interoperability of fuzzy spatiotemporal data from XML to object-oriented databases.
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