Peisheng Zhao

Semantics-based automatic composition of geospatial Web service chains

Recent developments in Web service technologies and the semantic Web have shown promise for automatic discovery, access, and use of Web services to quickly and efficiently solve particular application problems. One such application area is in the geospatial discipline, where Web services can significantly reduce the data volume and required computing resources at the end-user side. A key challenge in promoting widespread use of Web services in the geospatial applications is to automate the construction of a chain or process flow that involves multiple services and highly diversified and distributed data. This work presents an approach for automating geospatial Web service composition by employing geospatial semantics in the service-oriented architecture (SOA). It shows how ontology-based geospatial semantics are used in a prototype system for enabling the automatic discovery, access, and chaining of geospatial Web services. A case study of the chaining process for deriving a landslide susceptibility index illustrates the applicability of ontology-driven automatic Web service composition for geospatial applications.

The Geoprocessing Web

As Web services technology has matured in recent years, an increasing amount of geospatial resources and processing functions are available in the form of online Web services. Consequently, effective and efficient data processing methods for geospatial information extraction and knowledge discovery over the Web are a major challenge for research and industry. The Geoprocessing Web, which consists of light-weight protocols, crowd-sourcing capability, and the capability to process real-time geospatial data sources provided by sensors, enables distributed, interoperable and collaborative processing of geospatial data for information and knowledge discovery. This paper provides a comprehensive overview about the state-of-the-art architecture and technologies, and the most recent developments in the Geoprocessing Web.

Sharing geoscience algorithms in a Web service-oriented environment (GRASS GIS example)

Effective use of the large amounts of geospatial data available for geospatial research and applications is needed. In this paper, the emerging SOAP-based Web service technologies have been used to develop a large number of standard compliant, chainable geospatial Web services, using existing geospatial modules in software systems or specific geoscientific algorithms. A prototype for wrapping legacy software modules or geoscientific algorithms into loosely coupled Web services is proposed from an implementation viewpoint. Module development for Web services adheres to the Open GIS Consortium (OGC) geospatial implementation and the World Wide Web consortium (W3C) standards. The Web service interfaces are designed using Web Services Description Language (WSDL) documents. This paper presents how the granularity of an individual existing geospatial service module used by other geoscientific workflows is decided. A treatment of concurrence processes and clustered deployment of Web services is used to overcome multi-user access and network speed limit problems. This endeavor should allow extensive use of geoscientific algorithms and geospatial data.

Semantic Web Services‐based process planning for earth science applications

In a Web service‐based distributed environment, individual services must be chained together dynamically to solve a complex real world problem. The Semantic Web Service has shown promise for automatic chaining of Web services. This paper addresses semi‐automatic geospatial service chaining through Semantic Web Services‐based process planning. Process planning includes three phases: process modeling, process model instantiation and workflow execution. Ontologies and Artificial Intelligence (AI) planning methods are employed in process planning to help a user dynamically create an executable workflow for earth science applications. In particular, the approach was implemented in a common data and service environment enabled by interoperable standards from OGC and W3C. A case study of the chaining process for wildfire prediction illustrates the applicability of this approach.

BPELPower-A BPEL execution engine for geospatial web services

The Business Process Execution Language (BPEL) has become a popular choice for orchestrating and executing workflows in the Web environment. As one special kind of scientific workflow, geospatial Web processing workflows are data-intensive, deal with complex structures in data and geographic features, and execute automatically with limited human intervention. To enable the proper execution and coordination of geospatial workflows, a specially enhanced BPEL execution engine is required. BPELPower was designed, developed, and implemented as a generic BPEL execution engine with enhancements for executing geospatial workflows. The enhancements are especially in its capabilities in handling Geography Markup Language (GML) and standard geospatial Web services, such as the Web Processing Service (WPS) and the Web Feature Service (WFS). BPELPower has been used in several demonstrations over the decade. Two scenarios were discussed in detail to demonstrate the capabilities of BPELPower. That study showed a standard-compliant, Web-based approach for properly supporting geospatial processing, with the only enhancement at the implementation level. Pattern-based evaluation and performance improvement of the engine are discussed: BPELPower directly supports 22 workflow control patterns and 17 workflow data patterns. In the future, the engine will be enhanced with high performance parallel processing and broad Web paradigms.

Intelligent geospatial web services

A geospatial Web service is a modular application designed to enable the discovery, access, and chaining of geospatial information and services across the Web. Earth science applications are often both computingand data-intensive that involve diverse sources of data and complex processing functions. It is often not only time-consuming but also difficult to find, obtain, and process heterogeneous geospatial information. Web services provide a promising prospect to have most of data discovery and preprocessing work done automatically over the Web. In order to solve real-world geospatial problems through Web services, an “intelligent” mechanism is required to facilitate information discovery and integration over the network and automate the assembly of service chains. In this paper, we propose an intelligent geospatial Web service approach based on the Geo-Tree concept. This approach uses semantic-enriched “Geo-Object”, a component of “Geo-Tree”, to integrate the views of geospatial services and make them understandable and inferable, and adapts geospatial model-driven methods to automate service discovery, invocation and orchestration. Keywords-Geospatial Web Service; Geo-Object; Geo-Tree; Service Orchestration

Grid metadata catalog service-based OGC web registry service

Grid is a promising e-Science infrastructure that promotes and facilitates the sharing and collaboration in the use of distributed heterogeneous resources through Virtual Organization (VO). A critical factor to the overall utility of Grid is a scalable, flexible and robust registry mechanism. Although it provides some mechanisms to store and access metadata for publishing and discovering resources, such as MCS (Metadata Catalog Service), the Grid registry is inadequate for dealing with domain-specific resources. To enhance the earth science Grid systems, this paper presents a geospatial registry approach in which the OGC (Open GIS Consortium) WRS (Web Registry Service), a <i>de facto</i> standard that supports the publishing of and run-time access to geospatial resources, as a wrapper is used to extend the capabilities of the conventional Grid MCS to the processing of geospatial queries against multiple heterogeneous spatial data sources and services. The approach presented not only focuses on the specifics of descriptive information about spatial data, services, and relevant information objects, but also emphasizes using ontology to infer the semantic relationships between vocabularies for integrating different information models. The implementation of presented approach used in NASA Grid Data Service environment is also illustrated in this paper.

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.

Short communication: DEM Explorer: An online interoperable DEM data sharing and analysis system

Digital Elevation Model (DEM) data products are freely downloadable in tiled files from providers. But for most application needs, the area of interest does not exactly match the original spatial coverage of one DEM tile. After users obtain the files, they must mosaic, sub-set, and/or re-project them using geospatial software to generate the customized data that meet their requirements. It would be best if users could obtain the required DEM data directly. DEM Explorer is designed to share and explore the common DEM datasets in a publicly accessible online environment. It offers an intuitive and interoperable way to customize, download, visualize, and analyze DEM data in an Ajax-enabled Web interface. Via DEM Explorer, users are able to not only retrieve the original DEM files directly, but also obtain on-demand DEM data for any area of interest in a preferred format and projection. Deviations of terrain information are integrated as Web geoprocessing services in DEM Explorer to generate detailed terrain characteristics. DEM based hydrological models developed as Web services are aggregated to discover hydrological features. DEM Explorer has been adopted by the NASA Land Processes Distributed Active Archive Center to distribute the ASTER Global DEM to global users.