Automatic geospatial metadata generation for earth science virtual data products

Recent advances in Semantic Web and Web Service technologies has shown promise for automatically deriving geospatial information and knowledge from Earth science data distributed over the Web. In a service-oriented environment, the data, information, and knowledge are often consumed or produced by complex, distributed geoscientific workflows or service chains. In order for the chaining results to be consumable, sufficient metadata for data products to be delivered by service chains must be provided. This paper proposes automatic generation of geospatial metadata for Earth science virtual data products. A virtual data product is represented using process models, and can be materialized on demand by dynamically binding and chaining archived data and services, as opposed to requiring that Earth science data products be physically archived. Semantics-enabled geospatial metadata is generated, validated, and propagated during the materialization of a virtual data product. The generated metadata not only provides a context in which end-users can interpret data products before intensive execution of service chains, but also assures semantic consistency of the service chains.     

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.     

Agent-as-a-service-based geospatial service aggregation in the cloud: A case study of flood response

An Agent-as-a-Service (AaaS)-based geospatial service aggregation is proposed to build a more efficient, robust and intelligent geospatial service system in the Cloud for flood emergency response. It involves an AaaS infrastructure, encompassing the mechanisms and algorithms for geospatial Web Processing Service (WPS) generation, geoprocessing and aggregation. The method has the following advantages: 1) it allows separately hosted services and data to work together, avoiding transfers of large volumes of spatial data over the network; 2) it enriches geospatial service resources in the distributed environment by utilizing the agent cloning, migration and service regeneration capabilities of the AaaS, solving issues associated with lack of geospatial services to a certain extent; 3) it enables the migration of services to target nodes to finish a task, strengthening decentralization and enhancing the robustness of geospatial service aggregation; and 4) it helps domain experts and authorities solve interdisciplinary emergency issues using various Agent-generated geospatial services.     

Research challenges and perspectives of the Semantic Web

Accessing documents and services on today's Web requires human intelligence. The interface to these documents and services is the Web page, written in natural language, which humans must understand and act upon. The paper discusses the Semantic Web which will augment the current Web with formalized knowledge and data that computers can process. In the future, some services will mix human-readable and structured data so that both humans and computers can use them. Others will support formalized knowledge that only machines will use.     

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.     

A geoprocessing workflow system for environmental monitoring and integrated modelling

Environmental information infrastructure benefits from mainstream information technologies including workflow and service technologies. These technologies allow distributed geoprocessing algorithms, models, data, and sensors to be accessed through Web Services, which later can be chained together to support environmental monitoring and integrated modelling. Existing approaches on integrated environmental modelling, such as OpenMI, have advantages in enabling interoperability between modelling components. It is possible to integrate both of them to take the best from both approaches. The paper introduces the design and implementation of a geoprocessing workflow tool, named GeoJModelBuilder, which is able to integrate interoperable Sensor Web, geoprocessing services, and OpenMI-compliant model components into workflows. In this way, sensors, data, geoprocessing functions, and models could be integrated in a flexible, reusable, interoperable, and user-friendly way. The system has been published as an open source software and illustrated in cases on environmental monitoring and integrated modelling.     

一种基于业务流程执行描述语言的分布式Web服务发现方法

现有的Web服务发现方法主要是基于集中式拓扑，并且使用的服务描述仅仅是描述服务接口功能而忽略了业务流程执行相关信息，无法保证Web服务组合的相容性，也无法满足组合事务无死锁的要求。同时，这些方法都无法避免高维护代价、单点失效和可扩展性差等问题。本文提出一种基于结构化对等网络的Web服务发现方法，引入标识确定性有限状态机ADFSA（Annotated Deterministic Finite State Automata），将服务业务流程执行语言用于服务匹配，从而避免了潜在的Web服务组合不相容和有利于服务组合的自动化。     

空间数据网络处理服务模型及关键技术

面向空间数据处理的服务描述、部署、发现、调用过程是空间数据服务化处理的关键问题,直接关系到空间分析与相关数据处理计算的实现方式和执行效率。在标准网络服务模式之上,参照OGC规范设计空间数据网络过程处理服务的实现模型。并在空间数据分析和网络处理服务模型基础上,对网络服务的资源结构、服务调用模式、空间分析函数、数据处理流程等部分给出设计和定义。并以空间缓冲区分析算法为实例,实现过程处理服务模型实例,并给出分布式网络环境下空间数据处理服务的发布、调用与计算模式的完整实现方法。     

地球空间Web服务数据交换机制的设计与实现

为了支持多源、异构的地球空间数据在互联网上异步、可靠的传输,基于开放地理信息Web服务体系（OWS）,提出了基于消息中间件的空间数据交换方法。首先分析了当前地球空间数据交换的研究现状及相关技术,指出了当前地球空间数据交换方式存在效率低等诸多方面的不足,特别是由于目前很多OWS实现都是基于HTTP的Web服务模式,服务之间的数据交换是无状态和不可靠的。其次介绍了消息中间件规范,设计了基于消息中间件的空间数据交换体系结构,并对该体系结构的各组成部分进行了详细阐述。最后基于Java消息服务（JMS）、Web要素服务（WFS）、Web坐标转换服务（WCTS）和Web制图服务（WMS）,实现了一个基于消息中间件的空间数据交换系统实例,验证了方法的可行性。     

一种基于服务过程行为的Web服务发现方法

现有的web服务发现方法主要是基于集中式拓扑，并且使用的服务描述仅仅是描述服务接口功能而忽略了过程相关信息。这无法保证服务组合的相容性，也无法满足组合事务无死锁的要求。同时，这些方法都无法避免高维护代价、单点失效和可扩展性差等问题。本文提出一种基于结构化对等网络的Web服务发现方法，引入确定性有限状态机DFSA，将服务过程行为描述用于服务匹配，从而避免了潜在的Web服务组合不相客和有利于服务组合的自动化。     

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.     

Service-oriented applications for environmental models: Reusable geospatial services

Environmental modelling often requires a long iterative process of sourcing, reformatting, analyzing, and introducing various types of data into the model. Much of the data to be analyzed are geospatial data—digital terrain models (DTM), river basin boundaries, snow cover from satellite imagery, etc.—and so the modelling workflow typically involves the use of multiple desktop GIS and remote sensing software packages, with limited compatibility among them. Recent advances in service-oriented architectures (SOA) are allowing users to migrate from dedicated desktop solutions to on-line, loosely coupled, and standards-based services which accept source data, process them, and pass results as basic parameters to other intermediate services and/or then to the main model, which also may be made available on-line. This contribution presents a service-oriented application that addresses the issues of data accessibility and service interoperability for environmental models. Key model capabilities are implemented as geospatial services, which are combined to form complex services, and may be reused in other similar contexts. This work was carried out under the auspices of the AWARE project funded by the European programme Global Monitoring for Environment and Security (GMES). We show results of the service-oriented application applied to alpine runoff models, including the use of geospatial services facilitating discovery, access, processing and visualization of geospatial data in a distributed manner.     

面向语义服务结构中的服务接口问题研究

以往的服务接口模型没有规定业务伙伴任务的内部行为,这使业务处理难以准确地进行任务指派,也难以实现服务的按需组合以及业务处理模式的高度重用。为了克服上述问题并有效构建沟通服务提供者和需求者的桥梁,提出了面向语义服务结构的接口模型,该模型用抽象状态机抽象化描述和Web服务调用实例相关的服务行为,将服务交互的抽象和实现区分开,这既有效解决了服务双方的通讯和协作问题,便于交互模型的重用,而且为Web服务的自动发现、按需组合和智能推理提供了坚实的技术基础。     

Software trustworthiness 2.0—A semantic web enabled global source code analysis approach

There has been an ongoing trend toward collaborative software development using open and shared source code published in large software repositories on the Internet. While traditional source code analysis techniques perform well in single project contexts, new types of source code analysis techniques are ermerging, which focus on global source code analysis challenges. In this article, we discuss how the Semantic Web, can become an enabling technology to provide a standardized, formal, and semantic rich representations for modeling and analyzing large global source code corpora. Furthermore, inference services and other services provided by Semantic Web technologies can be used to support a variety of core source code analysis techniques, such as semantic code search, call graph construction, and clone detection. In this paper, we introduce SeCold, the first publicly available online linked data source code dataset for software engineering researchers and practitioners. Along with its dataset, SeCold also provides some Semantic Web enabled core services to support the analysis of Internet-scale source code repositories. We illustrated through several examples how this linked data combined with Semantic Web technologies can be harvested for different source code analysis tasks to support software trustworthiness. For the case studies, we combine both our linked-data set and Semantic Web enabled source code analysis services with knowledge extracted from StackOverflow, a crowdsourcing website. These case studies, we demonstrate that our approach is not only capable of crawling, processing, and scaling to traditional types of structured data (e.g., source code), but also supports emerging non-structured data sources, such as crowdsourced information (e.g., StackOverflow.com) to support a global source code analysis context.     

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.     

基于信誉的语义Web服务发现

服务发现在语义Web领域是一个挑战性问题.一个关键问题是发现满足用户功能需求的最佳服务.同样重要的是,电子商务应用还要求发现满足QoS需求的最佳服务.由此提出一个基于信誉管理的分布式服务选择框架.它主要有以下特点：用一个结构化的覆盖网络作为分布式服务存储系统来提高系统的有效性和可扩展性; 提出一个QoS感知的语义Web服务发现方法,并给出基于用户反馈的分布式信誉度评估算法.最后用一个例子示范算法如何解决实际问题.     

METEOR-S WSDI: A Scalable P2P Infrastructure of Registries for Semantic Publication and Discovery of Web Services

Web services are the new paradigm for distributed computing. They have much to offer towards interoperability of applications and integration of large scale distributed systems. To make Web services accessible to users, service providers use Web service registries to publish them. Current infrastructure of registries requires replication of all Web service publications in all Universal Business Registries. Large growth in number of Web services as well as the growth in the number of registries would make this replication impractical. In addition, the current Web service discovery mechanism is inefficient, as it does not support discovery based on the capabilities of the services, leading to a lot of irrelevant matches. Semantic discovery or matching of services is a promising approach to address this challenge. In this paper, we present a scalable, high performance environment for Web service publication and discovery among multiple registries. This work uses an ontology-based approach to organize registries into domains, enabling domain based classification of all Web services. Each of these registries supports semantic publication and discovery of Web services. We believe that the semantic approach suggested in this paper will significantly improve Web service publication and discovery involving a large number of registries. This paper describes the implementation and architecture of the METEOR-S Web Service Discovery Infrastructure, which leverages peer-to-peer computing as a scalable solution.