http://dl.gi.de/handle/20.500.12116/29090 2026-07-23T18:32:52Z http://dl.gi.de/handle/20.500.12116/29111 Combining the best of global-as-view and local-as-view for data integration Xu, Li; Embley, David W. Doroshenko, Anatoly E.; Halpin, Terry A.; Liddle, Stephen W.; Mayr, Heinrich C. Currently, there are two main basic approaches to data integration: Globalas-View (GAV) and Local-as-View (LAV). However, both GAV and LAV have their limitations. In a GAV approach, changes in information sources or adding a new information source requires revisions of a global schema and mappings between the global schema and source schemas. In a LAV approach, automating query reformulation has exponential time complexity with respect to query and source schema definitions. To resolve these problems, we offer TIQS as an alternative point of view that is neither GAV nor LAV. The approach uses source-to-target mappings based on a predefined conceptual target schema, which is specified ontologically and independently of any of the sources. The proposed data integration system is easier to maintain than both GAV and LAV, and query reformulation reduces to rule unfolding. Compared with other data integration approaches, our approach combines the advantages of GAV and LAV, mitigates the disadvantages, and provides an alternative for flexible and scalable data integration. 2004-01-01T00:00:00Z http://dl.gi.de/handle/20.500.12116/29109 An access control service for dynamic and hierarchical resources: Declarative model and implementation on top of XACML Psaila, Giuseppe; Biondi, Fulvio Doroshenko, Anatoly E.; Halpin, Terry A.; Liddle, Stephen W.; Mayr, Heinrich C. The increasing complexity of (distributed) information systems requires new solutions for dealing with access control problems. In particular, information systems are based on a large number of resources, with very complex structure, that must be accessed by a large variety of users. Traditional and instance based solutions are not adequate. In this paper, we propose a new approach to the problem. First of all, we define an access control model which is declarative, modular, hierarchical and instance independent, so that it is suitable for highly dynamic contexts. Then, we reports about the implementation of a Profile Service, which effectively exploits the XACML technology to simplify and shorten the development. 2004-01-01T00:00:00Z http://dl.gi.de/handle/20.500.12116/29110 Periodic scheduling in on-demand broadcast system Prabhu, Nitin; Kumar, Vijay; Ray, Indrakshi Doroshenko, Anatoly E.; Halpin, Terry A.; Liddle, Stephen W.; Mayr, Heinrich C. Recent advances in mobile computing have enabled the deployment of broadcast based information systems such as, wireless internet, traffic information systems, etc. These systems are mainly pull-based and their performance very much depends on the broadcast schedule they use. In this paper we focus on on-demand broadcast system. We propose a new ondemand scheduling algorithm that takes scheduling decision at periodic interval, unlike previous algorithms that take decision after broadcasting every data item. This reduces the time client spends monitoring the broadcast channel for data items. We study its behavior with a detailed simulation study and show that our algorithm performs better than the pervious algorithms for on-demand systems. 2004-01-01T00:00:00Z http://dl.gi.de/handle/20.500.12116/29107 A data transformation method based on schema mapping Li, You; Liu, Dongbo; Zhang, Wwiming Doroshenko, Anatoly E.; Halpin, Terry A.; Liddle, Stephen W.; Mayr, Heinrich C. Schema mapping is an important approach to solve the problem of data integration. This paper introduces a research prototype called SDE, which is a system for managing and facilitating the complex tasks of heterogeneous data transformation and integration. We also present a data transformation method based on schema mapping techniques. By analyzing the mappings and schemas it can automatically fulfill the task of data transformation and guarantee that the target result satisfies the target structure and constraints. It allows users to view the other participants' information as an extension of its own information system, without concerning for heterogeneity. 2004-01-01T00:00:00Z