15362390
Transforming Sem-ODM semantic schemas to DTDs
Exporting data in traditional databases as XML documents so that non-XML data can be accessed and exchanged seamlessly among applications has been studied in a number of projects. In this paper, we present an algorithm that automatically derives a Document Type Definition (DTD) from a Semantic Schema of the Semantic Binary Object-Oriented Data Model (Sem-ODM) based on the formal definitions of DTDs and Semantic Schemas. The structure and semantic information of a Semantic Schema is captured and expressed naturally in a DTD without applying any complicated operators or scanning the actual data stored in the database. Furthermore, the formalization of the two schemas connects the two data models and helps us better understand the capabilities brought about by publishing Sem-ODB data as XML.
3857492
Formal Representation and Transformation of DTDs to Sem-ODM Semantic Schemas
Many projects have investigated the issue of storing XML in traditional database systems and exporting data in traditional databases as XML documents. However, they paid little attention to the formalization of the data models and transformation between them. In this paper, we address this problem by providing a formal framework in which Document Type Definition (DTD) and Semantic Schema of the Semantic Binary ObjectOriented Data Model (Sem-ODM) are formally defined and the conversion from DTD to Semantic Schema is presented. Through this formalization, we achieve preciseness and conciseness in expressing both data models and converting one to the other.
3869043
XQuery Translation to Sem-SQL
XML query translation is an inevitable step involved in using non-XML databases storing XML data. In this paper, we address the XQuery to Sem-SQL translation issue, part of the XML storage and retrieval using the Semantic Binary Object-Oriented Database System (Sem-ODB) project, by providing a high-level description of the translation scheme between XQuery and Sem-SQL. Our translation scheme utilizes the navigation-oriented paradigm of Sem-SQL in translating XQuery path expressions to avoid excessive joins. Our approach can deal with all recursive path expressions without requiring the underlying database system to support recursive queries. We also extend the sorted outer union approach with consideration on user-defined orderings.
2470832
Statistical data reduction for efficient application performance monitoring
There is a growing need for systems that can monitor and analyze application performance data automatically in order to deliver reliable and sustained performance to applications. However, the continuously growing complexity of high performance computer systems and applications makes this process difficult. We introduce a statistical data reduction method that can be used to guide the selection of system metrics that are both necessary and sufficient to describe observed application behavior, thus reducing the instrumentation perturbation and data volume to be managed. To evaluate our strategy, we applied it to one CPU-bound grid application using cluster machines and GridFTP data transfer in a wide area testbed. A comparative study shows that our strategy produces better results than other techniques. It can reduce the number of system metrics to be managed by about 80%, while still capturing enough information for performance predictions.
52801820
Shape Reconstruction from 3D and 2D Data Using PDE-Based Deformable Surfaces
In this paper, we propose a new PDE-based methodology for deformable surfaces that is capable of automatically evolving its shape to capture the geometric boundary of the data and simultaneously discover its underlying topological structure. Our model can handle multiple types of data (such as volumetric data, 3D point clouds and 2D image data), using a common mathematical framework. The deformation behavior of the model is governed by partial differential equations (e.g. the weighted minimal surface flow). Unlike the level-set approach, our model always has an explicit representation of geometry and topology. The regularity of the model and the stability of the numerical integration process are ensured by a powerful Laplacian tangential smoothing operator. By allowing local adaptive refinement of the mesh, the model can accurately represent sharp features. We have applied our model for shape reconstruction from volumetric data, unorganized 3D point clouds and multiple view images. The versatility and robustness of our model allow its application to the challenging problem of multiple view reconstruction. Our approach is unique in its combination of simultaneous use of a high number of arbitrary camera views with an explicit mesh that is intuitive and easy-to-interact-with. Our model-based approach automatically selects the best views for reconstruction, allows for visibility checking and progressive refinement of the model as more images become available. The results of our extensive experiments on synthetic and real data demonstrate robustness, high reconstruction accuracy and visual quality.
15157401
Improving parallel data transfer times using predicted variances in shared networks
It is increasingly common to use multiple distributed storage systems as a single data store within which large datasets may be replicated. Thus, we face the problem of how to access replicated data efficiently. Multiple-source parallel transfers can reduce access times by transferring data from several replicas in parallel. However, we then face the problem of deciding which data to fetch from which replicas. We propose a Tuned Conservative scheduling technique that uses predicted means and variances for network performance to make data selection decisions. This stochastic scheduling technique adjusts the amount of data fetched on a link according to not only the link performance but the expected variance in that performance. We incorporate our technique into the striped GridFTP server from the Globus Toolkit, and demonstrate that the technique can produce data transfer times that are significantly faster and less variable than those of other techniques.
3393163
Dynamic Integration Strategy for Mediation Framework
The trend in the information area is to provide integrated access to diverse and dynamic information sources. We present a modeling and architectural solution to the problem of data integration from heterogeneous data sources based on the use of wrappers and mediators. The mediator supports integrated query processing by the semantic mapping between the global schema type and the local schema types. However, mediation poses extensive security problems. Protecting proprietary data from unauthorized access is recognized as one of the most significant barriers to the mediation systems. Our approach benefits in both flexible strategy of data integration based on semantic mappings and dynamic access control in mediation systems.
3410538
A Flexible Context-Aware Authorization Framework for Mediation Systems
Security is a critical concern for mediator-based data integration among heterogeneous data sources. This paper provides a modeling and architectural solution to the problem of mediation security that addresses the security challenges including context-awareness, semantic heterogeneity, and multiple security policy specification. A generic, extensible modeling method for the security policies in mediation systems is presented. A series of authorization constraints are identified based on the relationship on the different security components in the mediation systems. Moreover, we enforce the flexible access control to mediation systems while providing uniform access for heterogeneous data sources.