295 research outputs found
On incremental global update support in cooperative database systems
OzGateway is a cooperative database system designed for integrating heterogeneous existing information systems into an interoperable environment. It also aims to provide a gatewway for legacy information system migration. This paper summarises the problems and results of multidatabase transaction management research. In supporting global updates in OzGateway in an evolutionary way, we introduce a classification of multidatabase transactions and discuss the problems in each category. The architecture of OzGateway and the design of the global transaction manager and servers are presented
An Agent Based Transaction Manager for Multidatabase Systems
A multidatabase system (MDBMS) is a facility that allows users to access data located in multiple autonomous database management systems (DBMSs) at different sites. To ensure global atomicity for multidatabase transactions, a reliable global atomic commitment protocol is a possible solution. In this protocol a centralized transaction manager (TM) receives global transactions, submits subtransactions to the appropriate sites via AGENTS. An AGENT is a component of MDBS that runs on each site; AGENTS after receiving subtransactions from the transaction manager perform the transaction and send the results back to TM. We have presented a unique proof-of-concept, a JAVA application for an Agent Based Transaction Manager that preserves global atomicity. It provides a user friendly interface through which reliable atomic commitment protocol for global transaction execution in multidatabase environment can be visualized. We demonstrated with three different test case scenarios how the protocol works. This is useful in further research in this area where atomicity of transactions can be verified for protocol correctness
Integrity Constraint Checking in Federated Databases
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
Introducing Dynamic Behavior in Amalgamated Knowledge Bases
The problem of integrating knowledge from multiple and heterogeneous sources
is a fundamental issue in current information systems. In order to cope with
this problem, the concept of mediator has been introduced as a software
component providing intermediate services, linking data resources and
application programs, and making transparent the heterogeneity of the
underlying systems. In designing a mediator architecture, we believe that an
important aspect is the definition of a formal framework by which one is able
to model integration according to a declarative style. To this purpose, the use
of a logical approach seems very promising. Another important aspect is the
ability to model both static integration aspects, concerning query execution,
and dynamic ones, concerning data updates and their propagation among the
various data sources. Unfortunately, as far as we know, no formal proposals for
logically modeling mediator architectures both from a static and dynamic point
of view have already been developed. In this paper, we extend the framework for
amalgamated knowledge bases, presented by Subrahmanian, to deal with dynamic
aspects. The language we propose is based on the Active U-Datalog language, and
extends it with annotated logic and amalgamation concepts. We model the sources
of information and the mediator (also called supervisor) as Active U-Datalog
deductive databases, thus modeling queries, transactions, and active rules,
interpreted according to the PARK semantics. By using active rules, the system
can efficiently perform update propagation among different databases. The
result is a logical environment, integrating active and deductive rules, to
perform queries and update propagation in an heterogeneous mediated framework.Comment: Other Keywords: Deductive databases; Heterogeneous databases; Active
rules; Update
Location dependent transaction for mobile environment
With recent advances of mobile and portable devices,
more than one billion cellular phones in the world joined
by other wireless handheld computing devices like
personal digital assistants (PDAs) or pocket PCs, with
this number of users there are significant opportunities
for mobile commerce growth. Although mobile
commerce enables access to goods and service
regardless of the location of either buyer or seller, in
many situations the specific location of the buyer and
seller is critical to the transaction [1]. Also the time for
transaction execution become increasingly important not
from performance point view but also from the
corresponding relationship between the data and location
especially when the mobile user change its location
dynamically.
In this paper we aim to introduce a mobile transaction
model that takes into consideration the location
dependent transaction and the time constraint for mobile transaction execution
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