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Articles 631 - 640 of 640
Full-Text Articles in Physical Sciences and Mathematics
Executing Multidatabase Transactions, Mansoor Ansari, Marek Rusinkiewicz, Linda Ness, Amit P. Sheth
Executing Multidatabase Transactions, Mansoor Ansari, Marek Rusinkiewicz, Linda Ness, Amit P. Sheth
Kno.e.sis Publications
In a multidatabase environment, the traditional transaction model has been found to be too restrictive. Therefore, several extended transaction models have been proposed in which some of the requirements of transaction, such as isolation or atomicity, are optional. The authors describe one of such extensions, the flexible transaction model and discuss the scheduling of transactions involving multiple autonomous database systems managed by heterogeneous DBMS.
The scheduling algorithm for flexible transactions is implemented using L.0, a logically parallel language which provides a framework for concisely specifying the multidatabase transactions and for scheduling them. The key aspects of a flexible transaction specification, …
Specifying Interdatabase Dependencies In A Multidatabase Environment, Marek Rusinkiewicz, Amit P. Sheth, George Karabatis
Specifying Interdatabase Dependencies In A Multidatabase Environment, Marek Rusinkiewicz, Amit P. Sheth, George Karabatis
Kno.e.sis Publications
The problem of interdatabase dependencies and the effect they have on applications updating interdependent data are addressed. A model that allows specifications of constraints among multiple databases in a declarative fashion is proposed. The separation of the constraints from the application programs facilitates the maintenance of data constraints and allows flexibility in their implementation. It allows investigation of various mechanisms for enforcing the constraints, independently of the application programs. By grouping the constraints together, it is possible to check their completeness and discover possible contradictions among them. The concepts of polytransactions, which use interdatabase dependencies to generate a series of …
On The Relationship Between Parsimonious Covering And Boolean Minimization, Venu Dasigi, Krishnaprasad Thirunarayan
On The Relationship Between Parsimonious Covering And Boolean Minimization, Venu Dasigi, Krishnaprasad Thirunarayan
Kno.e.sis Publications
Minimization of Boolean switching functions is a basic problem in the design of logic circuits. The designer first comes up with a switching function expressed in terms of several binary input variables that satisfies the desired functionality, and then attempts to minimize the function as a sum of products or product of sums. It turns out that a sum of products form of a switching function that has no redundancy is a union of prime implicants of the function.
In this paper we would like to explicate some of the relationships of the boolean minimization problem to a formalization of …
The Architecture Of Braid: A System For Bridging Al/Db Systems, Amit P. Sheth, Anthony B. O'Hare
The Architecture Of Braid: A System For Bridging Al/Db Systems, Amit P. Sheth, Anthony B. O'Hare
Kno.e.sis Publications
We describe the design of BrAID (a Bridge between Artificial Intelligence and Database Management Systems), an experimental system for the efficient integration of logic based Artificial Intelligence (Al) and database (DB) technologies. Features provided by BrAID include (a) access to conventional DBMSs, (b) support for multiple inferencing strategies, (c) a powerful caching subsystem that manages views and employs subsumption to facilitate the reuse of previously cached data, (d) lazy or eager evaluation of queries submitted by the AI system, and (e) the generation of advice by the AI system to aid in cache management and query execution planning. To discuss …
On Serializability Of Multidatabase Transactions Through Forced Local Conflict, Dimitrios Georgakopoulos, Marek Rusinkiewicz, Amit P. Sheth
On Serializability Of Multidatabase Transactions Through Forced Local Conflict, Dimitrios Georgakopoulos, Marek Rusinkiewicz, Amit P. Sheth
Kno.e.sis Publications
The main difficulty in enforcing global serializability in a multidatabase environment lies in resolving indirect transitive conflicts between multidatabase transactions. Indirect conflicts introduced by local transactions are difficult to resolve because the behavior or even the existence of local transactions is not known to the multidatabase system. To overcome these problems, we propose to incorporate additional data manipulation operations in the subtransactions of each multidatabase transaction. We show that if these operations create direct conflicts between subtransactions at each participating local database system, indirect conflicts can be resolved even if the multidatabase system is not aware of their existence. Based …
Management Of Interdependent Data: Specifying Dependency And Consistency Requirements, Amit P. Sheth, Marek Rusinkiewicz
Management Of Interdependent Data: Specifying Dependency And Consistency Requirements, Amit P. Sheth, Marek Rusinkiewicz
Kno.e.sis Publications
Multiple databases that serve the needs of various application systems are considered. One of the significant problems in managing these databases is to maintain the related data items consistent to the required degree. This problem is frequently referred to as `redundant data management'. Since the term `redundancy' tends to imply that the data is unwanted or superfluous, the authors use the more general term `management of interdependent data'. Some preliminary ideas in this area are discussed. The problem of managing interdependent data is characterized, and some important types of interdatabase dependency are identified.
Attribute Relationships: An Impediment In Automating Schema Integration, Amit P. Sheth, Sunit K. Gala
Attribute Relationships: An Impediment In Automating Schema Integration, Amit P. Sheth, Sunit K. Gala
Kno.e.sis Publications
Success in schema integration depends on understanding the semantics of schema components (e.g., entity sets, relationship sets, attributes), and the ability to capture and reason about these semantics. An important objective of our work on schema integration is to automate the reasoning as much as possible, and when not possible, depend on the human input and guidance. A key results of comparing the semantics associated with schema objects is that of determining attribute relationship. Once attribute relationships are determined, the task of object class(e.g., entity sets and relationship sets) integration becomes simpler and can e automated to a great extent. …
Fault Tolerance In A Very Large Database System: A Strawman Analysis, Amit P. Sheth
Fault Tolerance In A Very Large Database System: A Strawman Analysis, Amit P. Sheth
Kno.e.sis Publications
A simple model is used to study the effect of fault-tolerance techniques and system design on system availability. A generic multiprocessor architecture is used that can be configured in different ways to study the effect of system architectures. Important parameters studied are different system architectures and hardware fault-tolerance techniques, mean time to failure of basic components, database size and distribution, interconnect capacity, etc. Quantitative analysis compares the relative effect of different parameter values. Results show that the effect of different parameter values on system availability can be very significant. System architecture, use of hardware fault tolerance (particularly mirroring), and data …
A Tool For Integrating Conceptual Schemas And User Views, Amit P. Sheth, James A. Larson, Aloysius Cornelio, Shamkant B. Navathe
A Tool For Integrating Conceptual Schemas And User Views, Amit P. Sheth, James A. Larson, Aloysius Cornelio, Shamkant B. Navathe
Kno.e.sis Publications
An interactive tool has been developed to assist database designers and administrators (DDA) in integrating schemas. It collects the information required for integration from a DDA, performs essential bookkeeping, and integrates schemas according to the semantics provided. The authors present the capabilities of this tool by discussing the integration methodology and the user interface of the tool.
An Analysis Of The Effect Of Network Load And Topology On The Performance Of Concurrency Control Algorithm In Distributed Database Systems, Anoop Singhal, Amit P. Sheth, Ming T. Liu
An Analysis Of The Effect Of Network Load And Topology On The Performance Of Concurrency Control Algorithm In Distributed Database Systems, Anoop Singhal, Amit P. Sheth, Ming T. Liu
Kno.e.sis Publications
Earlier studies in the performance analysis of concurrency control algorithms in distributed database systems (DDBS) have assumed that the message transmission time between any two nodes of a network is constant. Hence they disregard the effect of communication subnet related parameters such as network traffic, network topology, the capacity of transmission channels and the size of messages transmitted. In this paper an analytical model is used to estimate the delays in transmission channels for a DDBS in a long haul network. The analysis shows that the constant transmission time assumption cannot be justified in many cases and that response time …