38331434
Rule Discovery for Query Optimization
9033123
Process Aggregation Using Web Services
This paper examines the opportunities and challenges related to data and process integration architectures in the context of Web Services. A primary goal of most enterprises in today's economic environment is to improve productivity by streamlining and aggregating business processes. This paper illustrates how integration architectures based on Web Services offer new opportunities to improve productivity that are expedient and economical. First, the paper introduces the technical standards associated with Web Services and provides business example for illustration. Abstracting from this example, we introduce a concept we call Process Aggregation that incorporates data aggregation and workflow to improve productivity. We show that Web Services will have a major impact on Process Aggregation, making it both faster and less expensive to implement. Finally, we suggest some research directions relating to the Process Aggregation challenges facing Web Services that are not currently being addressed by standards bodies or software vendors. These include context mediation, trusted intermediaries, quality and source selection, licensing and payment mechanisms, and systems development tools.
3110757
Context Knowledge Representation and Reasoning in the Context Interchange System
The Context Interchange Project presents a unique approach to the problem of semantic conflict resolution among multiple heterogeneous data sources. The system presents a semantically meaningful view of the data to the receivers (e.g. user applications) for all the available data sources. The semantic conflicts are automatically detected and reconciled by a Context Mediator using the context knowledge associated with both the data sources and the data receivers. The results are collated and presented in the receiver context. The current implementation of the system provides access to flat files, classical relational databases, on-line databases, and web services. An example application, using actual financial information sources, is described along with a detailed description of the operation of the system for an example query.
38159603
The COntext INterchange (COIN) Project: Data Extraction and Interpretation from Semi-Structured Web Sources
17041428
Context interchange in a client-server architecture
Abstract Many organizations today require information from diverse information systems, and government efforts are moving toward a national information infrastructure for sharing information. However, the systems used by these organizations lack the capabilities to meaningfully translate information among semantically heterogeneous environments. Because the meaning of data acquired from a source environment is usually different from that needed or expected in the receiver's environment, the effectiveness of information exchange is dependent on the system's capability for context interchange, i.e., the representation, exchange, comparison, and transformation of context knowledge. We show here a practical means for developing context interchange capabilities in a client-server architecture by use of semantic values (i.e., data and their context(as the unit of data exchange. The key components in this architecture are the context mediator server, whose job is to identify and construct the semantic values being sent, determine when the exchange is meaningful, and convert the semantic values to the form required by the client (i.e., receiver), and the data environment server, whose job is to assist in the location, access, development, and maintenance of the context knowledge for all clients and servers.
2677077
Context interchange: new features and formalisms for the intelligent integration of information
The Context Interchange strategy presents a novel perspective for mediated data access in which semantic conflicts among heterogeneous systems are not identified a priori, but are detected and reconciled by a context mediator through comparison of contexts axioms corresponding to the systems engaged in data exchange. In this article, we show that queries formulated on shared views, export schema, and shared “ontologies” can be mediated in the same way using the Context Interchange framework. The proposed framework provides a logic-based object-oriented formalsim for representing and reasoning about data semantics in disparate systems, and has been validated in a prototype implementation providing mediated data access to both traditional and web-based information sources.
43742881
Erratum ("The small model property: how small can it be?" Volume 178, Number 1 [2002], pages 279-293)
15658777
Translation Validation: From SIGNAL to C
Translation validation is an alternative to the verification of translators (compilers, code generators). Rather than proving in advance that the compiler always produces a target code which correctly implements the source code (compiler verification), each individual translation (i.e. a run of the compiler) is followed by a validation phase which verifies that the target code produced on this run correctly implements the submitted source program. In order to be a practical alternative to compiler verification, a key feature of this validation is its full automation. 
 
Since the validation process attempts to "unravel" the transformation effected by the translators, its task becomes increasingly more difficult (and necessary) with the increase of sophistication and variety of the optimizations methods employed by the translator. In this paper we address the practicability of translation validation for highly optimizing, industrial code generators from Signal, a widely used synchronous language, to C. We introduce new abstraction techniques as part of the automation of our approach.
7986917
Translation Validation: From DC+ to C*
Translation validation is an alternative to the verification of translators (compilers, code generators). Rather than proving in advance that the compiler always produces a target code which correctly implements the source code (compiler verification), each individual translation (i.e. a run of the compiler) is followed by a validation phase which verifies that the target code produced on this run correctly implements the submitted source program. In order to be a practical alternative to compiler verification, a key feature of this validation is its full automation. 
 
In this paper we demonstrate the feasibility of translation validation for industrial code generators from DC+ -a widely used intermediate format for synchronous languages- to C. We explain the compilation pattern from DC+ to C and advocate new abstraction techniques for a fragment of first order logic as part of the automation of our approach.
30791016
Extending the Limits of Sequentially Phased Reasoning
Verification via abstraction is the topic of concluding correctness of a complicated program from correctness of an abstraction of this program. Principles for sequentially phased reasoning are examples of verification via abstraction. They use permutation equivalences to abstract concurrent programs which logically work in phases to considerably simpler variants which perform these phases sequentially. It is shown in this paper that there are classes of concurrent programs, such as self-stabilizing ones, which logically work in phases but cannot be abstracted to a sequentialized version using permutation equivalence. A new class of so-called Ω-equivalences is defined which generalizes permutation equivalence and stutter equivalence. It is proved that both equivalences are indeed special cases of Ω-equivalences. A verification strategy based on Ω-equivalences is formulated and compared with existing approaches for sequentially phased reasoning. The strategy is applied to a self-stabilizing coloring program that can neither be abstracted by permutation nor by stutter equivalences to a sequentialized version.
31386871
A Study of Singularity Formation in the Kelvin-Helmholtz Instability with Surface Tension
The possibility of singularity formation in vortex sheets acted on by surface tension is considered. In the evolution of a nearly flat vortex sheet with viscosity and surface tension neglected, Kelvin-Helmholtz instability has been shown to lead to the development of curvature singularities on the sheet. This is not unexpected, as the linearized equations of motion for this flow exhibit short-wavelength instability: infinitesimal perturbations grow at an infinite rate. Since the inclusion of surface tension stabilizes (on linear theory) the high-wavenumber modes, it has been presumed that it also suppresses the formation of singularities. The possibility of singularity formation is examined by generalizing Moore's approximation for vortex sheets to include the presence of surface tension. For the approximate theory, traveling wave solutions that develop singularities on the interface in finite time are found. Computations of the traveling wave solution are provided to reveal other features, and comparisons between these solutions and previously computed solutions of the full equations are made.