**4. Framework for a citation knowledge service system**

In the process of creating a citation knowledge service, we construct the citation knowledge base, the lightweight citation ontology base, and the domain ontology base by using ontology and other technologies. We use the ontology to reorganize the citation knowledge unit, organize, store, and query citation data in a machine-readable mode. According to user's search habits that captured user behavior preferences and knowledge preferences, the system is able to understand user needs and establish a matching knowledge discovery mechanism [36].

This chapter presents a framework of an ontology-based citation knowledge service system, which contains four core layers, a data resource layer, an ontology layer, a semantic association layer, and a functional layer, as shown in **Figure 6**.
