Scott Jensen

Visualization of network data provenance

Visualization facilitates the understanding of scientific data both through exploration and explanation of the visualized data. Provenance also contributes to the understanding of data by containing the contributing factors behind a result. The visualization of provenance, although supported in existing workflow management systems, generally focuses on small (medium) sized provenance data, lacking techniques to deal with big data with high complexity. This paper discusses visualization techniques developed for exploration and explanation of provenance, including layout algorithm, visual style, graph abstraction techniques, and graph matching algorithm, to deal with the high complexity. We demonstrate through application to two extensively analyzed case studies that involved provenance capture and use over three year projects, the first involving provenance of a satellite imagery ingest processing pipeline and the other of provenance in a large-scale computer network testbed.

Understanding Grid resource information management through a synthetic database benchmark/workload

Management of Grid resource information is a challenging, and important area considering the potential size of the Grid and wide range of resources that should be represented. Though example Grid Information Servers exist, behavior of these servers across different platforms is less well understood. This paper describes a study we undertook to compare the access language and platform capabilities for three different database platforms, relational, native XML, and LDAP, serving as a Grid information server. Our study measures query response times for a range of queries and highlights sensitivities exhibited by the different platforms to variables such as result set size and collection size.

Provenance Capture and Use in a Satellite Data Processing Pipeline

With the interdependencies that exist between data in a scientific processing pipeline, the ability to track the provenance of the scientific process through multiple stages is necessary to determining the usability of the resulting data product. In this paper, we study the capture of provenance from an existing NASA instrument ingest pipeline. Since instrumenting the scientific code for a production system is not feasible, we show how provenance events can be scavenged from log files to generate detailed provenance graphs. Through extensions to the Karma provenance system, which have been implemented on a test instance of the AMSR-E production data pipeline, we determine that when the volume of provenance information is high, provenance graph visualizations provide a good tool for monitoring the ingest pipeline and identifying processing differences in ways not seen before. Two novel uses of provenance that we present in this paper are comparisons between processing runs and forward provenance for viewing downstream dependencies.

Using Characteristics of Computational Science Schemas for Workflow Metadata Management

Computational science workflows are generating an ever-increasing volume of data products. Metadata for these workflows is communicated using one or more discipline-specific schemas and is not static but instead is subject to frequent updates and additions. In contrast to general XML data, the unique uses for scientific metadata allow further optimization.We propose a general metadata catalog for storing scientific metadata that is optimized for community science use and communicates metadata as XML using the schemas of scientific domains. In this paper we show that our hybrid approach outperforms the well-known inlining approach to storing XML when applied to scientific metadata.

Structure, sharing and preservation of scientific experiment data

In mesoscale meteorology, the quantity of information has increased significantly due to sophisticated data distribution schemes combined with developments in sensors and instruments capable of monitoring the lower several kilometers of the atmosphere at higher levels of resolution. This paper introduces myLEAD, a personalized information management tool for geoscience users. MyLEAD eases the data and information overload on the scientist by providing explicit solutions to the problems of structure, sharing, and preservation. This paper describes strategies within the myLEAD system to personalize data product and representation which ultimately leads to personalized workspaces and collaborative environments. We also include experimental results from some of the experiments that we conducted.

Senior travel buddies: sustainable ride-sharing & socialization

We are developing a system to be implemented at Continuing Care Retirement Communities (CCRCs) throughout the United States in an effort to encourage ride-sharing among residents in order to decrease their carbon emissions. We are focusing on senior citizens for two reasons. they are a growing segment of the population with driving habits that result in higher pollution, but they are also a population that is at risk of isolation and the mental and physical harm that can result from being isolated. Our system addresses both of these issues while leveraging the infrastructure and culture of CCRCs in addition to hiding the technology from the senior residents themselves.

A hybrid XML-relational grid metadata catalog

The ability to manage metadata is a critical requirement of the grid, but scientists have not been given the tools needed to catalog experimental data based on complex metadata attributes. Our research has shown that the specific characteristics of metadata catalogs require a different approach than that used for general queries over XML data. This paper presents a hybrid approach to storing XML in a relational database that exploits the specific characteristics of a metadata catalog

Personal Workspace for Large-Scale Data-Driven Computational Experiment

As the scale and complexity of data-driven computational science grows, so grows the burden on the scientists and students in managing the data products used and generated during experiments. Products must be moved and directories created. Search support in traditional file systems is arcane. While storage management tools can store rich metadata, these tools do not satisfy the nuances of the individual computational science researcher working alone or cooperatively. We have developed a personal workspace tool, myLEAD, that actively manages metadata and data products for users. Inspired by the Globus MCS metadata catalog and layered on top of the UK e-Science OGSA-DAI tool, myLEAD provides capture, storage and search tools to the computational scientist. In this paper we experimentally evaluate the performance of the myLEAD metadata catalog

Monitoring access to stateful resources in grid environments

Currently, grid technologies are widely used in large-scale scientific applications. Grids support stateful interactions with explicit exposure of state information across the boundaries of a service. In this paper, we present a stateful Web service architecture that provides efficient sharing of a service instance between heterogeneous service requesters with monitoring of the interactions. We describe how we compose the state information based on the formalized sequence of the interactions. We also describe how the shared service instance is managed, and interacted with, through standard Web services interfaces. We analyze the performance of our approach in a large-scale scientific grid application.

Trading Consistency for Scalability in Scientific Metadata

Long-term repositories that are able to represent the detailed descriptive metadata of scientific data have been recognized as key to both data reuse and preservation of the initial investment in generating the data. Detailed metadata captured during scientific investigation not only enables the efficient discovery of relevant data sets but also is a source for exploring ongoing activity. In XMC Cat metadata catalog, an XML catalog that uses a novel hybrid model to store XML to a relational database, we exploit differences in the temporal utility between browse and search metadata to selectively relax the consistency model used. By ensuring only eventual consistency on parts of the solution, we determine through experimental analysis that the performance and scalability of the catalog can be substantially improved.