26,482 research outputs found

    Protocols for Integrity Constraint Checking in Federated Databases

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    A federated database is comprised of multiple interconnected database systems that primarily operate independently but cooperate to a certain extent. Global integrity constraints can be very useful in federated databases, but the lack of global queries, global transaction mechanisms, and global concurrency control renders traditional constraint management techniques inapplicable. This paper presents a threefold contribution to integrity constraint checking in federated databases: (1) The problem of constraint checking in a federated database environment is clearly formulated. (2) A family of protocols for constraint checking is presented. (3) The differences across protocols in the family are analyzed with respect to system requirements, properties guaranteed by the protocols, and processing and communication costs. Thus, our work yields a suite of options from which a protocol can be chosen to suit the system capabilities and integrity requirements of a particular federated database environment

    Schema architecture and their relationships to transaction processing in distributed database systems

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    We discuss the different types of schema architectures which could be supported by distributed database systems, making a clear distinction between logical, physical, and federated distribution. We elaborate on the additional mapping information required in architecture based on logical distribution in order to support retrieval as well as update operations. We illustrate the problems in schema integration and data integration in multidatabase systems and discuss their impact on query processing. Finally, we discuss different issues relevant to the cooperation (or noncooperation) of local database systems in a heterogeneous multidatabase system and their relationship to the schema architecture and transaction processing

    The One-Box Challenge: Providing a Federated Search That Benefits the Research Process

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    The one-box federated search of databases brings as many challenges as promises to database searching, especially in terms of adapting these systems to user needs and the effects this new mode of searching will have on users' research behaviors. This issue of “The Balance Point” presents several librarians with strong interests in reference and instruction, who tell the story of adapting a federated search system for their libraries and reflect upon how federated searching can change the way students do research and on the implications federated searching has on information literacy skills and the quality of results found

    The role of expert systems in federated distributed multi-database systems/Ince Levent

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    A shared information system is a series of computer systems interconnected by some kind of communication network. There are data repositories residing on each computer. These data repositories must somehow be integrated. The purpose for using distributed and multi-database systems is to allow users to view collections of data repositories as if they were a single entity. Multidatabase systems, better known as heterogeneous multidatabase systems, are characterized by dissimilar data models, concurrency and optimization strategies and access methods. Unlike homogenous systems, the data models that compose the global database can be based on different types of data models. It is not necessary that all participant databases use the same data model. Federated distributed database systems are a special case of multidatabase systems. They are completely autonomous and do not rely on the global data dictionary to process distributed queries. Processing distributed query requests in federated databases is very difficult since there are multiple independent databases with their own rules for query optimization, deadlock detection, and concurrency. Expert systems can play a role in this type of environment by supplying a knowledge base that contains rules for data object conversion, rules for resolving naming conflicts, and rules for exchanging data.http://archive.org/details/theroleofexperts109459362Turkish Navy author.Approved for public release; distribution is unlimited

    Object-oriented modeling and design of database federations

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    We describe a logical architecture and a general semantic framework for precise specification of so-called database federations. A database federation provides for tight coupling of a collection of heterogeneous component databases into a global integrated system. Our approach to database federation integrates in a uniform and systematic manner the underlying database schemas of the component legacy systems to a separate, newly defined integrated database schema. This integrated database is completely virtual, and will constitute the actual federated database. That is, queries posed against the federated system will be posed against this virtual integrated database; these global queries will then be mapped by the mediator to actual local queries against the existing (legacy) component databases. Our approach is based upon the UML/OCL data model. UML is the de facto standard language for analysis and design in object-oriented frameworks, and is being employed more and more for analysis and design of Information systems, in particular information systems based on databases and their applications. Database specifications often involve specifications of constraints, and the Object Constraint Language (OCL) - as part of UML - can aid in the unambiguous modelling of database constraints. One of the central notions in database modelling and in constraint specifications is the notion of a database view; a database view closely corresponds to the notion of derived class in UML. We will employ OCL and the notion of derived class as a means to treat (inter-)database constraints and database views in a federated context. We will also offer a transaction model for a simple set of updates in database federations. The paper will demonstrate that our particular mediating system integrates component schemas without loss of constraint information. Furthermore, we will discuss a mapping of database specifications in terms of UML/OCL to the relational model.

    Vertical Federated Graph Neural Network for Recommender System

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    Conventional recommender systems are required to train the recommendation model using a centralized database. However, due to data privacy concerns, this is often impractical when multi-parties are involved in recommender system training. Federated learning appears as an excellent solution to the data isolation and privacy problem. Recently, Graph neural network (GNN) is becoming a promising approach for federated recommender systems. However, a key challenge is to conduct embedding propagation while preserving the privacy of the graph structure. Few studies have been conducted on the federated GNN-based recommender system. Our study proposes the first vertical federated GNN-based recommender system, called VerFedGNN. We design a framework to transmit: (i) the summation of neighbor embeddings using random projection, and (ii) gradients of public parameter perturbed by ternary quantization mechanism. Empirical studies show that VerFedGNN has competitive prediction accuracy with existing privacy preserving GNN frameworks while enhanced privacy protection for users' interaction information.Comment: 17 pages, 9 figure

    Integrity Constraint Checking in Federated Databases

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    A federated database is comprised of multiple interconnected databases that cooperate in an autonomous fashion. Global integrity constraints are very useful in federated databases, but the lack of global queries, global transaction mechanisms, and global concurrency control renders traditional constraint management techniques inapplicable. The paper presents a threefold contribution to integrity constraint checking in federated databases: (1) the problem of constraint checking in a federated database environment is clearly formulated; (2) a family of cooperative protocols for constraint checking is presented; (3) the differences across protocols in the family are analyzed with respect to system requirements, properties guaranteed, and costs involved. Thus, we provide a suite of options with protocols for various environments with specific system capabilities and integrity requirement
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