A Web Portal for Integrating and Sharing Geographic
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Chin-Te Jung1, Chih-Hong Sun2, Min-Fang Lien3, Chih-Shyang Chang4, Wei-Jen Chung5, Hong-Yang Lin6, Ping-Ying Tsai7 1 Ph.D., Department of Geography, National Taiwan University, Taipei city, Taiwan, No. 1, Sec. 4, Roosevelt Road, 106, Tel: +886-2-33665829, [email protected] 2 Professor, Department of Geography, National Taiwan University, Taipei city, Taiwan, No. 1, Sec. 4, Roosevelt Road, 106, Tel: +886-2-33665829, [email protected] * Corresponding author 3 Director of Technologies Department, Taiwan GIS Center, Taipei city, Taiwan, 6F, No. 6, Sec. 1, Roosevelt Road, 106, Tel: +886-2-23931122, [email protected] 4 Professor, Department of Information Management, Tungnan University, GEOGRAPHY New Taipei city, Taiwan, No. 152, Sec. 3, Beishen Road, 222, Tel: +886-2-86625945, [email protected] 37 5 Engineer, Taiwan GIS Center, Taipei city, Taiwan, 6F, No. 6, Sec. 1, Roosevelt Road, 106, Tel: +886-2-23931122, [email protected] 6 Engineer, Taiwan GIS Center, Taipei city, Taiwan, 6F, No. 6, Sec. 1, Roosevelt Road, 106, Tel: +886-2-23931122, [email protected] 7 Engineer, Taiwan GIS Center, Taipei city, Taiwan, 6F, No. 6, Sec. 1, Roosevelt Road, 106, Tel: +886-2-23931122, [email protected] MAKOCI: A WEB PORTAL FOR INTEGRATING AND SHARING GEOGRAPHIC INFORMATION SERVICES ABSTRACT. The lack of integration and KEYWORDS: Geographic Information Service, communication of various geographic Ontologies, Multi-agent System, Cyber infra- information services (GI services) has resulted structure in many duplication collection of earth observation data, and challenges of semantic INTRODUCTION interoperability. This paper proposes an ontology-based multi-agents platform, The explosive growth of the Internet in recent called MAKOCI (multi-agent knowledge years has led to significant advances in the oriented cyberinfrastructure), which acts as use of Web services, instead of conventional GI service one stop to manage, publish, software tools, for processing data and share, and discover GI services semantically. exchanging information [Kvaløy et al., 2005]. By ontologies, formal meanings of concepts In earth observations, observed data (e.g., are defined to annotate and discover GI satellite images or phenomenon measured services on a conceptual level for semantic by in-situ sensors) can be encoded into Web interoperability. With the assistance of services for sharing and communication. multi-agents, the processes in MAKOCI can The Open Geospatial Consortium (OGC) be divided into various modules and be recently has built a unique and revolutionary communicated based on the same semantics framework of open standards, called sensor in ontologies. A prototype was implemented Web enablement (SWE), for exploiting Web- to test MAKOCI. Finally, we conclude the connected sensors and sensor systems advantages and disadvantages of MAKOCI of all types: flood gauges, air pollution and point out several future works. monitors, stress gauges on bridges, mobile gi113.indd 37 22.03.2013 11:00:24 heart monitors, Webcams, satellite-borne semantic heterogeneity described above earth imaging devices and countless other hampered among users as well, especially sensors and sensor systems via Web services when they use different keywords to search [Jaeger et al., 2005]. The observed data by GI services in the platform. these sensors are often accompanied with geographical information, such as place Therefore, this study aims to develop an names or coordinates, and can be considered ontology-enabled multi-agent platform, as one type of geographic information services which facilitates ontologies to define common (GI services). With the assistance of OGC, there understandings for semantic interoperability, GEOGRAPHY are more standard formats for GI services, and uses multi agents to assist Web service such as geography markup language (GML), providers and consumers to register and 38 Web mapping service (WMS), Web feature discovery GI services in the platform. The service (WFS), and Web processing service platform is called multi-agent knowledge (WPS), have dominated the Web to perform oriented cyberinfrastructure (MAKOCI). We geospatial data acquisition and processes as divide GI services into two categories: data- well as information integration and exchange accessing services (Web services that provide [Peng and Tsou, 2003]. Nevertheless, while GIS data) and geoprocessing services (Web sharing and integrating heterogeneous GI services that analyze GIS data) [Lutz et al., services, a central platform for search required 2007]. The metadata of each GI service is GI services and semantically interoperate aimed to be registered into MAKOCI and these GI services [Egenhofer, 2002; Kuhn, use defined formal meanings in ontologies 2003] appear more critical. to annotate the registered metadata for semantic interoperability. The registered Semantic interoperability of geospatial data metadata is encoded in the resource has been recognized as the main hamper description framework (RDF) [Klyne and for integrating GI services [Fonseca and Carroll, 2004] so that Web service consumers Sheth, 2002]. It is because that different can search appropriate GI services not only terminology may be used to describe the by browsing categories or using keywords same phenomenon by different domains and but also by using SPARQL, a query language it lacks a common and shared understanding for RDF [Prud'Hommeaux and Seaborne, across the domains to interoperate and 2008], on the semantic level. communicate [Kuhn, 2003]. For example, one may use AirTemperature to describe This paper is organized as follows. Section 2 an observation of air temperature in a GI briefly introduces the background about service, whereas the other one may use ontologies, RDF, and multi agents. Section 3 ATemp to express the same observation. It presents the proposed framework of MAKOCI. will be difficult to integrate those two GI Section 4 shows an implemented prototype. services without a shared understanding on Section 5 concludes the advantages and the terminologies. disadvantages of the platform and points out some future works. In the other hand, a central platform, such as Geospatial One-Stop1, is lack for GI services BACKGROUND to be registered, discovered, and managed. Data providers can easily use GIS-Server Ontologies software, such as GeoServer2, to publish their In information science, an ontology is observation data into standard Web services defined as “an explicit specification of a over the Web. However, it may challenges for conceptualization” [Gruber, 1993], where a other users to use the Web services if they conceptualization is a way of “thinking about do not know where they are. In addition, a domain” [Uschold, 1998] whereas the formal meanings of both the types of concepts 1 http://geo.data.gov 2 http://geoserver.org/display/GEOS/Welcome and their relationships in a domain are ggi113.inddi113.indd 3388 222.03.20132.03.2013 111:00:241:00:24 delineated in a machine-readable language RDF by the explicit specifications for semantic The RDF is one of standard frameworks for interoperability and knowledge inference semantic Web recommended by World Wide [Benjamins et al., 1998]. By Ontologies, Web Consortium (W3C) [Klyne and Carroll, shared and common understandings (i.e., 2004]. The RDF aims to represent information semantics) can be communicated among in the Web by formal semantics, which can people and machines [Crubézy and Musen, be readable and accessible by machines 2003]. The formal meanings in an ontology to query and infer implicit information. The can be incorporated into data integration RDF encodes the information in of subject, processing [Peachavanish and Karimi, 2007], predicate, and object triplets [Klyne and GEOGRAPHY search algorithms [Bernard et al., 2003; Carroll, 2004; Bizer et al., 2009]. The subject Purves et al., 2007; Stock, 2008], and analytical and object of a triple are uniform resource 39 methods [Di et al., 2006; Lutz et al., 2007]. identifiers (URIs) to identify resources (e.g., concepts and individuals in ontologies) or The Web ontology language (OWL) is the XML schema datatype, whereas the predicate standard language of ontologies and is specifies the relationships between the recommended by W3C [McGuinness and subject and object, and is also represented Van Harmelen, 2004]. Basic elements of OWL by URIs [Bizer et al., 2009]. URI is similar to a include individuals, classes, and properties uniform resource locator (URL), which use (i.e., relationships) [Knublauch et al., 2004]. the http:// scheme to describe an address of a Individuals represent real instances in a website. However, URI provide a more generic domain, whereas classes represent concepts means to identify resources over the Web by that can be seen as collections of individuals the HTTP protocol [Klyne and Carroll, 2004]. of the same type. Properties are binary and directional links that connect individuals from For example, an RDF triple can state that one class (called the domain of the property) a GI service, Taiwan_River, has the polyline to another (called the range of the property). geometry, as shown in Fig. 1. The subject Properties can be classified on the basis of this and object of the triple are Taiwan_River and range into object and datatype properties the polyline geometry which is related by [McGuinness and Van Harmelen, 2004]. the predicate, hasGeometry. URIs are used Object properties link individuals, whereas to identify each resource in the RDF triple, datatype properties link