Facete A Generic Spatial Facetted Browser for RDF

Facete is a web application for the exploration of SPARQL-accessible spatial data, which offers several distinguishing features. First, there is the advanced faceted search component which enables users to filter the data by inverse properties and nested properties. Counts are provided for both facets and facet values. Second, the system will always attempt to detect (possible indirectly) related geometric information for the set of resources matched by the faceted search. For example, if a user filters by the class Person, then the system could detect that birthPlace and deathPlace provide geo-coordinates and appropriate suggestions about what to display on the map would be shown to the user. Third, Facete provides a map display capable of dealing with large amounts of geometric information. Finally, users are able to customize a tabular view for the data related to their facet selection. Information about Facete is available on its project site[1]. All of Facete's user interface components are based on the popular AngularJS[2] framework, and are published as a separate library called JAvascript Suite for Sparql Access (Jassa)[3]. In the remainder of this section, we give an overview of Facete's components, which we partly published in [14].

User Interface

Facete is implemented as a Single Page Application (SPA) whose user interface comprises several UI components, which are depicted in Fig. 6 and explained in the following. In the top area, there are elements that enable the user to select a SPARQL endpoint and chose from one or more of its contained named graphs. The main panel is divided into three columns containing a set of widgets with the following functionality:

1. Selection. The first widget, labeled Facet, shows a facet tree that corresponds to the properties of all resources that match the set constraint. If there

Fig. 6. Graphical user interface of facete

are no constraints, all resources that appear as a subject in the selected graphs are matched. Three actions can be performed for node in the facet tree. A click on the facet's name lists the facet's values in the Facet Value widget, where these values can be used for defining constraints. Clicking the caret symbol toggles the display of corresponding child facets. These are the properties of the selected facet's values. Lastly, a facet can be pinned as a column to the Table View. Note, that the root of the facet tree is formed by a facet labelled Items. This facet's values correspond to the set of resources in subject positions of the selected RDF graphs. The Facet Values widget enables a user to paginate through a selected facet's values and optionally filter these values by a search term. Furthermore, clicking the checkbox next to a value creates a constraint. The Filters widget lists all active constraints. Individual constraints can be removed by clicking their entry, whereas the Clear Filters button purges them all.

2. Data. The middle area contains the Table View, which lists a table whose content is based on resources that match the active constraints and the facets that were pinned as columns. Columns can be sorted by clicking the caret icons. Multiple orders are supported by holding the shift key down while clicking.

3. Geographical. The Geo-Link drop down menu enables the user to choose from property paths connecting the resources that match the constraints with those that can be shown on the map. By default, the option automatic is enabled, which always picks the shortest path among the found ones. The Map widget displays markers corresponding to the selected resources and the geo-link. Blue boxes indicate areas that contain too many markers to be shown at once. These boxes disappear when sufficiently zoomed in. Clicking a marker shows its details in the Detail View. The Detail View shows the excerpt of the Table View that corresponds to the selected marker(s).

  • [1] aksw.org/Projects/Facete
  • [2] angularjs.org/
  • [3] https://github.com/GeoKnow/Jassa-UI-Angular
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