Genong Yu

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.

Geo-processing workflow driven wildfire hot pixel detection under sensor web environment

Integrating Sensor Web Enablement (SWE) services with Geo-Processing Workflows (GPW) has become a bottleneck for Sensor Web-based applications, especially remote-sensing observations. This paper presents a common GPW framework for Sensor Web data service as part of the NASA Sensor Web project. This abstract framework includes abstract GPW model construction, GPW chains from service combination, and data retrieval components. The concrete framework consists of a data service node, a data processing node, a data presentation node, a Catalogue Service node, and a BPEL engine. An abstract model designer is used to design the top level GPW model, a model instantiation service is used to generate the concrete Business Process Execution Language (BPEL), and the BPEL execution engine is adopted. This framework is used to generate several kinds of data: raw data from live sensors, coverage or feature data, geospatial products, or sensor maps. A prototype, including a model designer, model instantiation service, and GPW engine-BPELPower is presented. A scenario for an EO-1 Sensor Web data service for wildfire hot pixel detection is used to test the feasibility of the proposed framework. The execution time and influences of the EO-1 live Hyperion data wildfire classification service framework are evaluated. The benefits and high performance of the proposed framework are discussed. The experiments of EO-1 live Hyperion data wildfire classification service show that this framework can improve the quality of services for sensor data retrieval and processing.

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.

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

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.

Building an on-demand web service system for Global Agricultural Drought Monitoring and Forecasting

There is an urgent need but remains a very challenging problem to provide worldwide users with timely, on-demand, and ready-to-use agricultural drought data and information. The latest advances in Web service, geospatial interoperability and cyber-infrastructure technologies and the availability of near real-time global remote sensing data promise a solution to the problem. This paper presents the research study of the state of the art, methodology and approaches to building an open, interoperable, on-demand Web service system for global agriculture drought monitoring and forecasting. The implemented system, named as Global Agriculture Drought Monitoring and Forecasting System (GADMFS), overcomes most limitations of current agriculture drought information systems in the world and significantly improves global agriculture drought monitoring, prediction and analysis with advanced geospatial Web service technology.

Metadata requirements analysis for the emerging Sensor Web This was orally presented at the European Geosciences Union General Assembly 2008, Vienna, Austria, 13–18 April 2008.

Abstract The Sensor Web has emerged from Earth Science research with the development of Web technology, to achieve process automation, sensor interoperation, and service synergy. These promises require the discovery of the right sensor at the right time and the right location with the right quality. Metadata, for sensor, platform, and data, are crucial for achieving such goals. However, analysis and practical use of these metadata reveals that the metadata and their associations are not applicable or suitable for the Sensor Web. The shortfalls are (1) the non-standard metadata expression language; (2) the missing link between sensor and domain knowledge; (3) the insufficiency in the information for geographic locating and sensor tasking; and (4) the enhanced requirements on the quality, security, and ownership of both sensors and their sensed data. This paper reviews the current standards that have metadata components for the sensor and its platform, especially those from ISO TC211, Open Geospatial Consortium Inc., and The National Aeronautics and Space Administration Global Change Master Directory . A recommendation on metadata that meets the requirement of cross-mission sensor discovery in a pervasive Web environment is derived from them. The recommendation addresses issues on language formalization, sensor geolocation, semantics, quality, and accessibility. Roles of the emerging semantic Web technology for enabling robust discovery of sensor are discussed.