In this paper, we propose a standpoint-based Linked Data visualization system, as a step in the development of a Linked Data visualization system that receives an entity and visualizes the data related to it in various ways based on multiple \standpoints". Here, a standpoint denotes the data generated from a user's perspective of interest in an entity and its visualization. For example, \volcano" and \World Heritage Site" are standpoints with respect to Mt. Fuji. Considering these standpoints, a user interested in \volcano" in our system is shown various types of volcanoes and the history of volcanic eruptions, whereas a user interested in \World Heritage Site" is shown a list of viewing spots and the list of visitor numbers per year. This feature is not found in existing Linked Data browsers which can be de ned as \single" standpoint browsers. In this paper, we present our proposed approach and describe a prototype system based on the proposed approach.
In recent years, there has been increasing use of Linked Data as a method for
publishing data on the Web[
A number of visualization approaches have been proposed. Pubby[
Our proposed approach is to incorporate a mechanism for handling multiple \standpoints" in the method adopted by Information Workbench and Linked Data Reactor. In this paper, a standpoint denotes the data generated from a user's perspective of interest regarding an entity and its visualization.
Consider the case of visualizing the entity Mt. Fuji; in this case, \volcano" and \World Heritage Site" are example standpoints with respect to Mt. Fuji. Considering these standpoints, to a user interested in \volcano" our proposed approach will show various types of volcanoes and the history of volcanic eruption; to a user interested in \World Heritage Site" it will show a list of viewing spots and a list of visitor numbers per year.
Our proposed approach adopted a dynamic semantic publishing publishing receives a \viewpoint" and \standpoints" and then displays the data using a view corresponding to each of them. Here, \viewpoint" an entity used to start the search; for example, in the current case, the viewpoint is a mountain such as \Mt. Fuji", \Mt. Aso", \Sakurajima", \Yakushima", and each of these examples are represented as a Uniform Resource Identi er (URI). The term \standpoints" refers to a class of an entity, for example, \volcano", \World Heritage Site", and \island".
Page is constructed manually. First, we develop a view part called by a gadget. A gadget consist of a pair of a query and a visualization code same as Sgvizler, D3SPARQL or SemwidgJS etc. Next, set constructed gadgets in a page , nally, corespond a class to a page. Gadgets can be reused in other pages. If our proposed approach receive an entity as a \viewpoint", then it visualizes a page corresponding a class of an entity as \standpoints".
In this section, we describe our prototype system. The prototype is equipped on LOD4LL1; for more details, the viewer can be found at https://lod4all.net/ frontend/.
The prototype system receives a URI corresponding to an entity as a \viewpoint" or an entity related a keyword as a \viewpoint". By using keyword search, the prototype system presents a list of URIs related to the keyword. Therefore, even if the user does not know the entity's URI that corresponds to the \viewpoint", the user can determine the entity's URI by using the keyword search function. The prototype system uses a rdf:type in an entity as \standpoints", and does not receive \standpoints" as a user input.
The prototype system visualize the data by a de nition corresponding to a rdf:type from the entity. Fig.1 shows an example of visualization for the case of \Kawasaki Frontale (http://dbpedia.org/resource/Kawasaki_Frontale)"2.
When Kawasaki Frontale is regarded as \Sports Team (http://dbpedia. org/ontology/SportsTeam)", the prototype system visualizes a hometown, a league name, an age distribution, and a list of players (See:https://lod4all. net/frontend/page/display?uri=http%3A//dbpedia.org/resource/Kawasaki_ Frontale&page_id=SportsTeam). When Kawasaki Frontale is regarded as \Company (http://dbpedia.org/ontology/Company)", the prototype system visualizes a president name, owner companies, and companies of same owner(See:https: //lod4all.net/frontend/page/display?uri=http%3A//dbpedia.org/resource/ Kawasaki_Frontale&page_id=Company). An image display part and a description display part are used by both pages. These are a same part on both pages.
The prototype has a similar page search function, and when there is no page for the type given to the entity, the system searches for an equivalent type 1 https://lod4all.net/ (accessed Sep. 2018) 2 Kawasaki Frontale is the soccer club sponsored by FUJITSU in Japan . (\http://www.w3.org/2002/07/owl#equivalentClass") or a parent type(\http: //www.w3.org/2000/01/rdf-schema#subClassOf"), if the page is de ned for the type. If a page corresponding to one of these types is found, then the prototype attempts to visualize the entity according to these types. If the similar page search function does not nd the page, then the prototype visualizes the entity using the default page. The entity has no class, then the prototype also visualizes the entity using the default page. The default page is a simple page, for example, provided by the Linked Data browser. 5
We proposed a standpoint-based Linked Data visualization approach. Our proposed approach can visualize the data related to it in various ways based on multiple \standpoints". In this work, we con rmed that it is important to assign ontology about data, when utilizing data based on our approach using a dynamic semantic publishing. In the future, a Linked Data service developer can develop APIs by using this approach. This means that the proposal method is also a standpoint-based Linked Data reconstruction approach.