Making More Ogc Services Available on the Web Discoverable for the Sdi Community

Kliment, Tomáš; Kliment, Marcel; Cetl, Vlado; Tuchyna, Martin

doi:10.5593/sgem2015/b22/s11.120

Cited by 4 publications

(9 citation statements)

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“…Table 7. Table 7 indicates that the proposed approach discovers a considerably larger number of WMSs than those found by the previous works of Li et al [16], Lopez-Pellicer et al [26], Kliment et al [27] and two well-known websites [80,81]. These previous works did not focus on a particular domain and they all searched for general WMSs.…”

Section: Sources Mandatory Abstractcontrasting

confidence: 41%

“…However, as time goes on, the number of WMS naturally increases, which affects the credibility of the comparison. Therefore, the number of services found by Kliment et al [27] and the two well-known websites [80,81] was tracked again on 27 April 2016. A total of 4233 WMSs with 2922 available WMSs were found in the website [82] provided by Kliment et al [27].…”

Section: Sources Mandatory Abstractmentioning

confidence: 99%

“…Therefore, the number of services found by Kliment et al [27] and the two well-known websites [80,81] was tracked again on 27 April 2016. A total of 4233 WMSs with 2922 available WMSs were found in the website [82] provided by Kliment et al [27]. In addition, a total of 8618 and 4029 WMSs were found by the two well-known websites [80,81], respectively.…”

Section: Sources Mandatory Abstractmentioning

confidence: 99%

“…In the last two years, Bone et al [32] designed a geospatial search engine for discovering multi-format geospatial data using the Google search engine with both user-specified and predefined terms. Kliment et al [27,39] used the advanced query operators "inurl:" of the Google search engine to discover specific OGC geospatial services stored in Google's indexes. This type of discovery approach is easily implemented, is low cost and can avoid the performance issues of systems that attempt to crawl the entire web [32].…”

Section: Surface Geospatial Web Services Discoverymentioning

confidence: 99%

“…The first type of discovery approach utilizes the application programming interfaces (APIs) of general-purpose search engines, employing predefined queries to search the Internet for discovering OGC geospatial web services [27,32,33,37,38]. For example, the Refractions Research OGC Survey [37] used the Google web API with two queries "request = getcapabilities" and "request = capabilities" to extract the results and then used a number of Perl "regular expressions" for a complete capabilities URL in each returned page.…”

Section: Surface Geospatial Web Services Discoverymentioning

confidence: 99%

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Discovering Land Cover Web Map Services from the Deep Web with JavaScript Invocation Rules

Hou

Chen

2016

IJGI

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Automatic discovery of isolated land cover web map services (LCWMSs) can potentially help in sharing land cover data. Currently, various search engine-based and crawler-based approaches have been developed for finding services dispersed throughout the surface web. In fact, with the prevalence of geospatial web applications, a considerable number of LCWMSs are hidden in JavaScript code, which belongs to the deep web. However, discovering LCWMSs from JavaScript code remains an open challenge. This paper aims to solve this challenge by proposing a focused deep web crawler for finding more LCWMSs from deep web JavaScript code and the surface web. First, the names of a group of JavaScript links are abstracted as initial judgements. Through name matching, these judgements are utilized to judge whether or not the fetched webpages contain predefined JavaScript links that may prompt JavaScript code to invoke WMSs. Secondly, some JavaScript invocation functions and URL formats for WMS are summarized as JavaScript invocation rules from prior knowledge of how WMSs are employed and coded in JavaScript. These invocation rules are used to identify the JavaScript code for extracting candidate WMSs through rule matching. The above two operations are incorporated into a traditional focused crawling strategy situated between the tasks of fetching webpages and parsing webpages. Thirdly, LCWMSs are selected by matching services with a set of land cover keywords. Moreover, a search engine for LCWMSs is implemented that uses the focused deep web crawler to retrieve and integrate the LCWMSs it discovers. In the first experiment, eight online geospatial web applications serve as seed URLs (Uniform Resource Locators) and crawling scopes; the proposed crawler addresses only the JavaScript code in these eight applications. All 32 available WMSs hidden in JavaScript code were found using the proposed crawler, while not one WMS was discovered through the focused crawler-based approach. This result shows that the proposed crawler has the ability to discover WMSs hidden in JavaScript code. The second experiment uses 4842 seed URLs updated daily. The crawler found a total of 17,874 available WMSs, of which 11,901 were LCWMSs. Our approach discovered a greater number of services than those found using previous approaches. It indicates that the proposed crawler has a large advantage in discovering LCWMSs from the surface web and from JavaScript code. Furthermore, a simple case study demonstrates that the designed LCWMS search engine represents an important step towards realizing land cover information integration for global mapping and monitoring purposes.

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Section: Sources Mandatory Abstractcontrasting

confidence: 41%

Section: Sources Mandatory Abstractmentioning

confidence: 99%

Section: Sources Mandatory Abstractmentioning

confidence: 99%

Section: Surface Geospatial Web Services Discoverymentioning

confidence: 99%

Section: Surface Geospatial Web Services Discoverymentioning

confidence: 99%

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Discovering Land Cover Web Map Services from the Deep Web with JavaScript Invocation Rules

Hou

Chen

2016

IJGI

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Borderless Geospatial Web (Bolegweb)

Cetl

Kliment

2016

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:The effective access and use of geospatial information (GI) resources acquires a critical value of importance in modern knowledge based society. Standard web services defined by Open Geospatial Consortium (OGC) are frequently used within the implementations of spatial data infrastructures (SDIs) to facilitate discovery and use of geospatial data. This data is stored in databases located in a layer, called the invisible web, thus are ignored by search engines. SDI uses a catalogue (discovery) service for the web as a gateway to the GI world through the metadata defined by ISO standards, which are structurally diverse to OGC metadata. Therefore, a crosswalk needs to be implemented to bridge the OGC resources discovered on mainstream web with those documented by metadata in an SDI to enrich its information extent. A public global wide and user friendly portal of OGC resources available on the web ensures and enhances the use of GI within a multidisciplinary context and bridges the geospatial web from the end-user perspective, thus opens its borders to everybody.Project "Crosswalking the layers of geospatial information resources to enable a borderless geospatial web" with the acronym BOLEGWEB is ongoing as a postdoctoral research project at the Faculty of Geodesy, University of Zagreb in Croatia (http://bolegweb.geof.unizg.hr/). The research leading to the results of the project has received funding from the European Union Seventh Framework Programme (FP7 2007 under Marie Curie FP7-PEOPLE-2011-COFUND. The project started in the November 2014 and is planned to be finished by the end of 2016. This paper provides an overview of the project, research questions and methodology, so far achieved results and future steps.

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