8691336
Effectiveness for Embedded Spheres and Balls
Abstract We consider arbitrary dimensional spheres and closed balls embedded in Rn as ⫫01 classes. Such a strong restriction on the topology of a ⫫01 class has computability theoretic repercussions. Algebraic topology plays a crucial role in our exploration of these consequences; the use of homology chains as computational objects allows us to take algorithmic advantage of the topological structure of our ⫫01 classes. We show that a sphere embedded as a ⫫01 class is necessarily located, i.e., the distance to the class is a computable function, or equivalently, the class contains a computably enumerable dense set of computable points. Similarly, a ball embedded as a ⫫01 class has a dense set of computable points, though not necessarily c.e. To prove location for balls, it is sufficient to assume that both it and its boundary sphere are ⫫01. However, the converse fails, even for arcs; using a priority argument, we prove that there is a located arc in R2 without computable endpoints. Finally, the requirement that the embedding map itself be computable is shown to be stronger than the other effectiveness criteria considered. A characterization in terms of computable local contractibility is stated the proof will be the subject of a sequel.
7900596
On self-embeddings of computable linear orderings
The Dushnik{Miller Theorem states that every innite countable linear ordering has a nontrivial self-embedding. We examine computability-theoretical aspects of this classical theorem.
1173889
Effectiveness for infinite variable words and the Dual Ramsey Theorem
Abstract.We examine the Dual Ramsey Theorem and two related combinatorial principles VW(k,l) and OVW(k,l) from the perspectives of reverse mathematics and effective mathematics. We give a statement of the Dual Ramsey Theorem for open colorings in second order arithmetic and formalize work of Carlson and Simpson [1] to show that this statement implies ACA0 over RCA0. We show that neither VW(2,2) nor OVW(2,2) is provable in WKL0. These results give partial answers to questions posed by Friedman and Simpson [3].
6824501
The Undecidability of Iterated Modal Relativization
In dynamic epistemic logic and other fields, it is natural to consider relativization as an operator taking sentences to sentences. When using the ideas and methods of dynamic logic, one would like to iterate operators. This leads to iterated relativization. We are also concerned with the transitive closure operation, due to its connection to common knowledge. We show that for three fragments of the logic of iterated relativization and transitive closure, the satisfiability problems are fi1 Σ11–complete. Two of these fragments do not include transitive closure. We also show that the question of whether a sentence in these fragments has a finite (tree) model is fi0 Σ01–complete. These results go via reduction to problems concerning domino systems.
25032718
Using simulation to facilitate effective workflow adaptation
In order to support realistic real-world processes, workflow systems need to be able to adapt to changes. Detecting the need to change and deciding what changes to carry out are very difficult. Simulation analysis can play an important role in this. It can be used in tuning quality of service metrics and exploring "what-if" questions. Before a change is actually made, its possible effects can be explored with simulation. To facilitate rapid feedback, the workflow system (METEOR) and simulation system (JSIM) need to interoperate. In particular, workflow specification documents need to be translated into simulation model specification documents so that the new model can be executed/animated on-the-fly. Fortunately, modern Web technology (e.g., XML, DTD, XSLT) make this relatively straightforward. The utility of using simulation in adapting a workflow is illustrated with an example from a genome workflow.
9935746
The JSIM web-based simulation environment
Abstract In its ideal form, web-based simulation should allow simulation models as well as simulation results to be as readily distributable and composable as today’s web documents. The rapid advances in web technology, most notably Java, are helping to make this a possibility. Support for executable web content, universal portability, component technology, and standard high-level packages for accessing databases and producing graphical user interfaces are important enablers of web-based simulation. Component-based software can be used to develop highly modular simulation environments supporting high reusability of software components. Because of the potentially large scope of web-based simulation, greater demands are placed on simulation environments. They should support rapid visual model development, access to local and remote databases, techniques for executing models or federations of models in a variety of ways, and embedding of simulation within larger systems. The use of component technology in the JSIM web-based simulation environment allows simulation models to be treated as components that can be dynamically assembled to build model federations. It also allows simulation inputs and outputs to be dynamically linked to database systems, making storage of simulation results easy and flexible.
15950590
Model instantiation for query driven simulation in active KDL
The focus of this paper is on how Active KDL can be used to provide a very powerful simulation support environment. Active KDL (Knowledge/Data Language) is an object-oriented database programming language, which provides access to integrated model, knowledge, and data bases. Simulation inputs and outputs can be stored by Active KDL since it supports complex objects. More importantly, Active KDL also allows users to specify rules to capture heuristic knowledge and methods to specify procedural behavior. Finally, Active KDL provides a simple mechanism for specifying concurrent execution, namely tasks embedded in active objects. These facilities provide a powerful mechanism for building simulation models out of pre-existing model components. These capabilities provide a tight coupling between a SIMODULA-like simulation system and a knowledge/database system, supporting query driven simulation, where model instantiation is used for information generation.
8657310
Constraint driven Web service composition in METEOR-S
Creating Web processes using Web service technology gives us the opportunity for selecting new services, which best suit our need at the moment. Doing this automatically requires us to quantify our criteria for selection. In addition, there are challenging issues of correctness and optimality. We present a constraint driven Web service composition tool in METEOR-S, which allows the process designers to bind Web services to an abstract process, based on business and process constraints and generate an executable process. Our approach is to reduce much of the service composition problem to a constraint satisfaction problem. It uses a multiphase approach for constraint analysis. This work was done as part of the METEORS framework, which aims to support the complete lifecycle of semantic Web processes.
11647322
Hembase: browser and genome portal for hematology and erythroid biology
Hembase (http://hembase.niddk.nih.gov) is an integrated browser and genome portal designed for web-based examination of the human erythroid transcriptome. To date, Hembase contains 15,752 entries from erythroblast Expressed Sequenced Tags (ESTs) and 380 referenced genes relevant for erythropoiesis. The database is organized to provide a cytogenetic band position, a unique name as well as a concise annotation for each entry. Search queries may be performed by name, keyword or cytogenetic location. Search results are linked to primary sequence data and three major human genome browsers for access to information considered current at the time of each search. Hembase provides interested scientists and clinical hematologists with a genome-based approach toward the study of erythroid biology.