**3. Method and process**

Any citation analysis method based on ontology and linked data mainly includes the following three steps: first, building citation ontology according to the bibliographic citation data and full-text citation information; second, using the citation ontology to normalize the reference information and publish the data to linked data according to the RDF model; and, third, in order to extract the required citation information, writing a specific SPARQL search query for a citation analysis dimension and executing the search query. The search results are then visualized to reach the citation analysis goals.

#### **3.1. Citation ontology construction**

From the perspective of citation analysis, bibliographic citation information and full-text citation information are not only two independent parts but also two important sources of data that are both necessary for citation analysis. Here, we construct the bibliographic citation ontology (BCO) and full-text citation ontology (FCO) based on the bibliographic citation information and the full-text citation information, respectively. This allows us to achieve comprehensive semantic annotation of the citation information at hand.

The most commonly used ontology construction methods are the IDEF-5 [29], skeletal methodology [30], KACTUS [31], TOVE [32], METHONTOLOGY [33], and seven-step methodology [34]. The purpose of this study was to construct a task-based ontology to describe citation information, so we choose the seven-step method developed by the Stanford University. The seven steps are (1) defining the domain and category of the ontology, (2) examining the possibility of reusing existing ontologies, (3) listing the important terms in the ontology, (4) defining the hierarchical system of classes, (5) defining the properties of the classes, (6) defining the facets of the properties, and (7) creating the instance. We also use the most popular protégé as our ontology development tool.

In recent years, with the advance of ontology, related studies have revealed that ontologybased knowledge services have been developed in different areas, including personalized medicine [19], e-government [20], medicine [21, 22], smart homes [23], the digital library [24, 25],

The digital library is an important application area of ontology-based knowledge service research. In 2015, Patkar [26] indicated that ontology is one of the latest tools for information retrieval from libraries in this digital age. His paper discusses advances in information managing tools and concludes by highlighting the applications of ontology among the different fields. Koutsomitropoulos, Solomo, and Papatheodorou [27] studied the semantic search service of the DSpace digital repository system. They argued that Semantic Search v2 introduces a structured query mechanism that makes querying easier and improves the design of the system, performance, and scalability. Queries based on the DSpace ontology were dynamically created, and DSpace was able to obtain structured knowledge from the available metadata. Empirical and quantitative evaluation has shown that such a system can conduct semantic searches that provide better services for inexperienced users, such as the use of new query

In 2015, Iorio and Schaerf [28] proposed a semantic model defined by the Sapienza Digital Library to describe resource metadata. The semantic model is derived from the metadata object description model (a digital library descriptive standard). A top-level conceptual reference model supports the implementation of semantic web technologies for digital library metadata.

Any citation analysis method based on ontology and linked data mainly includes the following three steps: first, building citation ontology according to the bibliographic citation data and full-text citation information; second, using the citation ontology to normalize the reference information and publish the data to linked data according to the RDF model; and, third, in order to extract the required citation information, writing a specific SPARQL search query for a citation analysis dimension and executing the search query. The search results are then

From the perspective of citation analysis, bibliographic citation information and full-text citation information are not only two independent parts but also two important sources of data that are both necessary for citation analysis. Here, we construct the bibliographic citation ontology (BCO) and full-text citation ontology (FCO) based on the bibliographic citation information and the full-text citation information, respectively. This allows us to achieve com-

The most commonly used ontology construction methods are the IDEF-5 [29], skeletal methodology [30], KACTUS [31], TOVE [32], METHONTOLOGY [33], and seven-step methodology [34]. The purpose of this study was to construct a task-based ontology to describe citation

prehensive semantic annotation of the citation information at hand.

and so on.

198 Scientometrics

dimensions, with clear benefits.

**3. Method and process**

visualized to reach the citation analysis goals.

**3.1. Citation ontology construction**

The construction of BCO is based on references. From the list of references, information such as the author, periodical, document type, year, volume period, and page number are extracted as the classes of BCO. In order to extend the dimensions of citation analysis, we extend the subclass from the perspective of journal and author. The "reference number" class is also added to the article, and the importance of the reference is measured by the quantities of internal references and external references. For property definitions, we reused the alreadyexisting ontology properties (e.g., "fabio: hasPublicationYear," "bibo: volume") and marked the newly added attributes in the form of "bco." An example of the BCO ontology's classes and properties is shown in **Figure 1**.

The construction of FCO begins with three aspects: citation function, citation sentiment, and citation position. The citation function represents the role of cited work to citing work, such as background development, data support, methodology support, extension, or refutation. Citation sentiment expresses the emotion attitude from citing work to cited work, such as positive, neutral, and negative. Citation position indicates the location of the paragraph where the reference behavior occurs, such as the "Introduction" section of the document. An example of the FCO ontology's classes and properties is shown in **Figure 2**.

**Figure 1.** Example classes and properties of bibliographic citation ontology.

**Figure 2.** Classes and properties of full-text citation ontology.
