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.     

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.     

基于REST的空间信息服务互操作协议的研究

REST式的Web服务充分地利用HTTP协议的分布式特性,可以使Web服务的开发变得更加高效、简洁、 可维护。着力于REST式空间信息服务互操作协议研究,通过分离OGC Web服务定义中的动作、意图和表示的方 式,确定服务中的资源。最后将REST的“资源”概念与空间信息“数据”共享结合起来,利用H"I"I'P协议定义的操作, 设计了RES"I'式空间信息服务互操作规范REST=WMS与REST-WFS.     

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.     

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。     

Geospatial information infrastructures to address spatial needs in health: Collaboration,challenges and opportunities

Most health-related issues such as public health outbreaks and epidemiological threats are better understood from a spatial–temporal perspective and, clearly demand related geospatial datasets and services so that decision makers may jointly make informed decisions and coordinate response plans. Although current health applications support a kind of geospatial features, these are still disconnected from the wide range of geospatial services and datasets that geospatial information infrastructures may bring into health. In this paper we are questioning the hypothesis whether geospatial information infrastructures, in terms of standards-based geospatial services, technologies, and data models as operational assets already in place, can be exploited by health applications for which the geospatial dimension is of great importance. This may be certainly addressed by defining better collaboration strategies to uncover and promote geospatial assets to the health community. We discuss the value of collaboration, as well as the opportunities that geographic information infrastructures offer to address geospatial challenges in health applications.     

Improving geographic information retrieval in spatial data infrastructures

In recent years, spatial data infrastructures (SDIs) have gained great popularity as a solution to facilitate interoperable access to geospatial data offered by different agencies. In order to enhance the data retrieval process, current infrastructures usually offer a catalog service. Nevertheless, such catalog services still have important limitations that make it difficult for users to find the geospatial data that they are interested in. Some current catalog drawbacks include the use of a single record to describe all the feature types offered by a service, the lack of formal means to describe the semantics of the underlying data, and the lack of an effective ranking metric to organize the results retrieved from a query. Aiming to overcome these limitations, this article proposes SESDI (Semantically-Enabled Spatial Data Infrastructures), which is framework that reuses techniques of classic information retrieval to improve geographic data retrieval in a SDI. Moreover, the framework proposes several ranking metrics to solve spatial, semantic, temporal and multidimensional queries.     

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.     

Analysis and assessment of a knowledge based smart city architecture providing service APIs

The main technical issues regarding smart city solutions are related to data gathering, aggregation, reasoning, data analytics, access, and service delivering via Smart City APIs (Application Program Interfaces). Different kinds of Smart City APIs enable smart city services and applications, while their effectiveness depends on the architectural solutions to pass from data to services for city users and operators, exploiting data analytics, and presenting services via APIs.Therefore, there is a strong activity on defining smart city architectures to cope with this complexity, putting in place a significant range of different kinds of services and processes. In this paper, the work performed in the context of Sii-Mobility smart city project on defining a smart city architecture addressing a wide range of processes and data is presented. To this end, comparisons of the state of the art solutions of smart city architectures for data aggregation and for Smart City API are presented by putting in evidence the usage semantic ontologies and knowledge base in the data aggregation in the production of smart services. The solution proposed aggregate and re-conciliate data (open and private, static and real time) by using reasoning/smart algorithms for enabling sophisticated service delivering via Smart City API. The work presented has been developed in the context of the Sii-Mobility national smart city project on mobility and transport integrated with smart city services with the aim of reaching a more sustainable mobility and transport systems. Sii-Mobility is grounded on Km4City ontology and tools for smart city data aggregation, analytics support and service production exploiting smart city API. To this end, Sii-Mobility/Km4City APIs have been compared to the state of the art solutions. Moreover, the proposed architecture has been assessed in terms of performance, computational and network costs in terms of measures that can be easily performed on private cloud on premise. The computational costs and workloads of the data ingestion and data analytics processes have been assessed to identify suitable measures to estimate needed resources. Finally, the API consumption related data in the recent period are presented.     

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.     

面向地理标记语言空间数据的地理信息聚合

针对地理标记语言(GML)空间数据的开放、可自我描述以及离散分布等特性,为了从海量GML空间数据中获取有针对性的整合应用,实现对GML空间数据的动态聚合,基于地理简易信息聚合(GeoRSS)标准,提出了面向GML空间数据的聚合映射模型,并设计了四层的集成框架体系结构及其工作流程。依据此体系结构,开发了GML空间数据地理信息聚合原型系统,并进行了相关实验,实现了对GML空间数据的有效聚合,验证了面向GML空间数据的地理信息聚合方法的可行性和聚合模型的可用性。该聚合方法使用户能够快速地从海量GML空间信息数据中获取更有目标性的数据,实现对已有数据的挑选、分析、归类,以及快速更新与整合集成等具体应用。     

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.     

PolarHub: A large-scale web crawling engine for OGC service discovery in cyberinfrastructure

The advancement of geospatial interoperability research has fostered the proliferation of geospatial resources that are shared and made publicly available on the Web. However, their increasingly availability has made the identification of the web signature of voluminous geospatial resources a major challenge. In this paper, we introduce our solution of a new cyberinfrastructure platform, the PolarHub, that conducts large-scale web crawling to discover distributed geospatial data and service resources and accomplish this goal efficiently and effectively. The PolarHub is built-upon a service-oriented architecture (SOA) and adopts Data Access Object (DAO)-based software design pattern to ensure the extendibility of the software system. The proposed meta-search-based seed selection and pattern-matching based crawling strategy facilitates the rapid resource identification and discovery through constraining the search scope on the Web. In addition, PolarHub introduces the use of advanced asynchronous communication strategy, which combines client-pull and server-push to ensure high efficiency of the crawling system. These unique design features of PolarHub enable a high performance, scalable, sustainable, collaborative, and interactive platform for active geospatial data discovery. Because of OGC's widespread adoption, OGC-compliant web services become the primary search target of PolarHub. Currently, the PolarHub system is up and running and is serving various scientific community that demands geospatial data. We consider PolarHub a significant contribution to the field of information retrieval and geospatial interoperability.     

在DNSSEC下保障顶级域名解析托管服务稳定迁移的操作机制

基于顶级域解析服务托管平台迁移部署实践,重点研究分析了在DNSSEC环境下,为避免发生域名系统安全扩展(DNSSEC,DNS security extension)信任链及解析服务中断、域名NS记录不一致等安全问题,如何在密钥轮转、DS和NS记录变更、数据更新等环节中实现新旧服务托管商及互联网数字分配机构(IANA,i...     

基于订阅/发布服务的广域信息管理系统应急响应机制

广域信息管理系统(SWIM)是一个分布式的大型网络系统,它实时地向空中交通管理部门、航空机场和航空公司等提供不间断的航空信息数据共享和传输服务。为了保障SWIM服务的连续性,研究了基于订阅/发布服务的SWIM系统应急响应机制。首先,根据实时监测SWIM网络的各性能指标,提出了基于改进的模糊层次分析的网络可生存性评估方法;其次,当SWIM网络生存性指标下降到低于参量的边界值时,发布相应信息到订阅者,由订阅者确定是否进行服务漂移;最后,分别针对自然灾害和分布式拒绝服务(DDoS)攻击两种情况,提出了基于订阅/发布服务的SWIM应急响应模型(ERMSP),该模型以订阅发布和信任管理机制为基础。仿真实验结果表明,通过对网络性能各指标的实时监测和部署ERMSP,可抵抗性提高了8.9%,业务连续性提高了18.2%,可以实现SWIM的应急响应。