Yaxing Wei

Integrating semantic web technologies and geospatial catalog services for geospatial information discovery and processing in cyberinfrastructure

A geospatial catalogue service provides a network-based meta-information repository and interface for advertising and discovering shared geospatial data and services. Descriptive information (i.e., metadata) for geospatial data and services is structured and organized in catalogue services. The approaches currently available for searching and using that information are often inadequate. Semantic Web technologies show promise for better discovery methods by exploiting the underlying semantics. Such development needs special attention from the Cyberinfrastructure perspective, so that the traditional focus on discovery of and access to geospatial data can be expanded to support the increased demand for processing of geospatial information and discovery of knowledge. Semantic descriptions for geospatial data, services, and geoprocessing service chains are structured, organized, and registered through extending elements in the ebXML Registry Information Model (ebRIM) of a geospatial catalogue service, which follows the interface specifications of the Open Geospatial Consortium (OGC) Catalogue Services for the Web (CSW). The process models for geoprocessing service chains, as a type of geospatial knowledge, are captured, registered, and discoverable. Semantics-enhanced discovery for geospatial data, services/service chains, and process models is described. Semantic search middleware that can support virtual data product materialization is developed for the geospatial catalogue service. The creation of such a semantics-enhanced geospatial catalogue service is important in meeting the demands for geospatial information discovery and analysis in Cyberinfrastructure.

Use of grid computing for modeling virtual geospatial products

Earth science research and applications usually use Distributed Geospatial Information Processing (DGIP) services and powerful computing capabilities to extract information and knowledge from large volumes of distributed geospatial data. Conceptually, such processing can be abstracted into a logical model that utilizes geospatial domain knowledge to produce new geospatial products. Using this idea, the geo-tree concept and the proposed geospatial Abstract Information Model (AIM) have been used to develop a Grid workflow engine complying with geospatial standards and the Business Process Execution Language. Upon a users request, the engine generates virtual geospatial data/information/knowledge products from existing DGIP data and services. This article details how to (1) define and describe the AIM in XML format, (2) describe the process logically with an AIM, including the geospatial semantic logic, (3) conceptually describe the process of producing a particular geospatial product step by step from raw geospatial data, (4) instantiate AIM as a concrete Grid-service workflow by selecting the optimal service instances and data sets, and (5) design a Grid workflow engine to execute the concrete workflows to produce geospatial products. To verify the advantages and applicability of this Grid-enabled virtual geospatial product system, its performance is evaluated, and a sample application is provided.

Towards a geospatial Catalogue federation Service

As geospatial catalogues are becoming accessible online through public query interfaces, a federation to fulfill distributed and integrated metadata discovery needs to be built. This study investigates the feasibility of federating three distinct geospatial catalogue services: the NASA Earth Observing System (EOS) ClearingHOuse (ECHO), the George Mason University (GMU) OpenGIS Catalogue Service for Web (CSW), and the U.S. Department of Energy (DOE) Earth System Grid (ESG) Simulation Data Catalogue. Challenges and problems in dealing with the metadata conceptual models, query languages, and communication protocols are analyzed. Proposed federation strategies and the operational federation system are introduced. Our results show that protocol adaptation, query dispatching, query criteria translation, and query results integration are the four main challenges in building a catalogue federation. A mediatorwrapper based approach can be adopted to build a federation service. The OpenGIS Catalogue Service specification can be used to define the internal communication protocols between the federation service and the affiliated catalogue services, and between the federation service and its clients.

Use of ebRIM-based CSW with sensor observation services for registry and discovery of remote-sensing observations

Recent advances in Sensor Web geospatial data capture, such as high-resolution in satellite imagery and Web-ready data processing and modeling technologies, have led to the generation of large numbers of datasets from real-time or near real-time observations and measurements. Finding which sensor or data complies with criteria such as specific times, locations, and scales has become a bottleneck for Sensor Web-based applications, especially remote-sensing observations. In this paper, an architecture for use of the integration Sensor Observation Service (SOS) with the Open Geospatial Consortium (OGC) Catalogue Service-Web profile (CSW) is put forward. The architecture consists of a distributed geospatial sensor observation service, a geospatial catalogue service based on the ebXML Registry Information Model (ebRIM), SOS search and registry middleware, and a geospatial sensor portal. The SOS search and registry middleware finds the potential SOS, generating data granule information and inserting the records into CSW. The contents and sequence of the services, the available observations, and the metadata of the observations registry are described. A prototype system is designed and implemented using the service middleware technology and a standard interface and protocol. The feasibility and the response time of registry and retrieval of observations are evaluated using a realistic Earth Observing-1 (EO-1) SOS scenario. Extracting information from SOS requires the same execution time as record generation for CSW. The average data retrieval response time in SOS+CSW mode is 17.6% of that of the SOS-alone mode. The proposed architecture has the more advantages of SOS search and observation data retrieval than the existing sensor Web enabled systems.

A taxonomy of geospatial services for global service discovery and interoperability

Geospatial service taxonomies represent the knowledge about the characteristics of geospatial services from the enterprise, computational, information, engineering, infrastructure, or technology viewpoints. This paper presents a lightweight taxonomy of geospatial services with the aim of promoting the global sharing of and interoperability among geospatial service instances. This taxonomy focuses on the knowledge connected with service interoperability. As a hierarchical taxonomy, it consists of six layers: service category, service type, version, profile, binding and uniform resource name (URN), from the root down to the leaves. Each layer is composed of classification nodes, with each node identifying one classification concept. Each concept, with a concrete semantic meaning, can be used to classify service instances. The application of this classification scheme to the Global Earth Observation System of Systems (GEOSS) Component and Service registry is also introduced. The results of this study may lead to the further development of service taxonomy to thoroughly capture the knowledge about geospatial services. The lessons learned may be useful to others representing and manipulating geoscientific knowledge.

Sharing geospatial provenance in a service-oriented environment

One of the earliest investigations of provenance was inspired by applications in GIS in the early 1990’s. Provenance records the processing history of a data product. It provides an information context to help users determine the reliability of data products. Conventional provenance applications in GIS focus on provenance capture, representation, and usage in a stand-alone environment such as a desktop-based GIS software system. They cannot support wide sharing and open access of provenance in a distributed environment. The growth of service-oriented sharing and processing of geospatial data brings some new challenges in provenance-aware applications. One is how to share geospatial provenance in an interoperable way. This paper describes the development of provenance service for geospatial data products using the ebXML Registry Information Model (ebRIM) of a geospatial catalog service, which follows the interface specifications of the OGC Catalogue Services for the Web (CSW). This approach fits well the current service stack of the GIS domain and facilitates the management of geospatial data provenance in an open and distributed environment.

Semantic Augmentations for Geospatial Catalogue Service

Catalogue service plays an important role in helping requestors to find the suitable geospatial data and services over the Web. The Open Geospatial Consortium has developed and recommended an ebRIM profile of Catalogue Services for the Web for implementing a catalogue service. Metadata for data and services registered in CSW is described by following the existing geographic metadata standards usually. The search functionality is limited to the direct match of keywords from metadata without fully utilizing the semantic information implicitly embedded in the metadata, such as hierarchical relationships among metadata entities. Web Ontology Language (OWL) provides a mechanism to enable the use of semantics. OWL-S uses OWL to describe the semantics for Web service. This paper explores the semantic representation of geospatial data and services to enable the semantic search in CSW based on the semantic relationship defined in OWL/OWL-S. Such semantics are organized in CSW through extending ebRIM

Semantic Web-based geospatial knowledge transformation

Earth and space science research and applications typically involve collecting and analyzing large volumes of geospatial data much of which is derived from other existing data by applying a scientific workflow. Such a step-by-step process can be viewed as a process of geospatial knowledge transformation, which often involves hypotheses, inferences and integrations to derive user-specific data products from the knowledge of domain experts. Our research is focused on reducing the transformation effort by providing component inference and integration tools. The Semantic Web envisions a new standardized information infrastructure to enable interoperable machine-to-machine interactions and automatic or semi-automatic service chaining for deriving knowledge over networks. This paper describes a generic framework and implementation of how the Semantic Web proceeds through the life cycle of geospatial knowledge transformation, from geospatial modeling (knowledge formalization), through model instantiation (service chain) to model execution (data product). Our approach relies on semantic integrations. A number of ontologies used to capture domain knowledge are introduced in this paper as the basis of knowledge bases for describing and reasoning geospatial data and services. Also, a semantically enabled geospatial catalog service is described to enable more effective discovery, automation and integration of geospatial data and services.

The design and implementation of a grid-enabled catalogue service

Catalogue service is crucial to the sharing and utilizing of geographic information. This paper provides a new architecture and its implementation of a geographic information catalogue service that can effectively manage distributed geographic data and services. The catalogue service is based on the Open Geospatial Consortium (OGC) Catalogue Service for Web Specification and the ebXML Registry Information Model (ebRIM). The ebRIM is extended with ISO 19115 (including draft part 2) and ISO 19119 international standards for better description of geographic information. The adoption of the ebRIM and international standards will greatly advance the interoperability of the catalogue service and the sharing of the abundant geographic information. The catalogue service is Gridenabled to facilitate Grid’s abilities of on-demand, ubiquitous access to distributed computing, data, and services resources. The Grid-enabled catalogue service is GSI-supported which enables it to interoperate with other Grid Services in a secure way. By being integrated with RLS, MDS and other Gridenabled OGC Services, this Grid-enabled catalogue service prototype provides secure discovery, retrieval, and management of geographic data and services.

An Optimized Grid-Based, OGC Standards-Compliant Collaborative Software System for Serving NASA Geospatial Data

It is now common for academic institutes, government sectors and commercial corporations all over the world to engage in collaborative, complex applications. Most of them require international and interoperable access to large quantities of distributed, heterogeneous geospatial data, services, computing abilities and other facilities. The open grid services architecture (OGSA) implemented through the globus toolkit, provides an applicable and convenient software infrastructure for securely sharing computational resources within a virtual organization. In this paper, based on the globus toolkit, we propose an open, reusable, optimized, standards-compliant, and grid-enabled geospatial software system for archiving, managing, querying and serving NASA earth observing system data. We apply grid technologies to OGC Web services to make them grid-enabled and deploy them into the system. These services can be invoked either by OGC users or by grid users in the grid environment. Any OGSA-compliant grid services can be deployed into the system, and can invoke or be invoked by our or other grid services in our virtual organization to securely access each others data and other computational resources after we authorize access. A catalogue service federation (CSF) with an OGC standard interface is developed to interact with other grid or non-grid geospatial catalogue services for querying and serving much more geospatial data. An intelligent grid service mediator (iGSM) and replica optimization service (ROS), both of which are grid services, are proposed to distribute and optimize user requests for data and services in the system. All of the grid-enabled geospatial services can be reused to construct more complex and functional services by forming a service-chain