2017 2nd International Conference on Wireless Communication and Network Engineering (WCNE 2017) ISBN: 978-1-60595-531-5 Research on Implementation of Knowledge Convergence Based on Jena System Xia-bai YANG1,*, Ming YANG1 and Yu HUANG2 1Yunnan College of Finance and Economics, Kunming 650222,China 2Kunming Railway Vocational Technical College, Kunming 650208,china *Corresponding author Keywords: Semantic Web, Knowledge convergence, Union operation, Intersection operation, Difference operation, Jena, RDF, RDFS, OWL, Triple. Abstract. With the development of Semantic Web technology, the discussion of RDF knowledge has been rapidly accumulating. To systematically converge the existing knowledge as well as the ever-emerging knowledge, it is required to conduct both existing and new building knowledge of RDF in terms of Union, Intersection and Difference operations, and to generate new knowledge which is the convergence discussed above. Based on API that is provided by Jena system, this paper implements knowledge convergence between two RDF files through the Java programming. Introduction Tim Berners-Lee, the inventor of the WWW(World Wide Web), proposed the Semantic Web technology for building Web based on the current Web technologies in 2001[1]. It is expected that the Web could obtain not only structural characteristics, but also semantic properties through the XML(Extensible Markup Language), RDF (Resource Description Framework), and KE(Knowledge Engineering) technologies. The main task of the Semantic Web is to make it more convenient for computers to process and find the huge amount of data in the WWW. The objectives are to make the user become an all-powerful God, that is almost an omniscience to the vast resources on the Internet, and, by using the ‘Computer Intelligence Agents’, to release human beings from the heavy labor of searching related web pages selecting useful information quickly and accurately[2]. Within the decade, there are lots of research in this field. Based on the study of the semantic network architecture and Jena's system architecture[3], this paper conducts a research on Union, Intersection and Difference operations of the existing RDF knowledge and the new RDF knowledge, and uses Java programming to realize Union, Intersection and Difference operations between two RDF files based on API that is provided by Jena system. Jena 2 Architecture Jena is a free and open-source Java framework for constructing semantic Web and related data applications[4]. The first version of Jena1 was released in 2000, the most recent version was Apache-jena-3.5.0 released in 2017. Jena 2.1 (Jena) is used in this article. Jena provides RDF, Triple store and OWL(Web Ontology Language) platform for research on Semantic web. Jena provides Java API for establishing and manipulating RDF graph according to RDF model and RDFS syntax specification. The RDF graph supports the Union, Intersection and Difference operations. Jena system is structured by Graph, EnhGraph, and Model three layers, as shown in Figure 1. The Graph Layer is mainly for storing triplets, the EnhGraph Layer implements multiple views for graphs and nodes, and the Model Layer provides application programmers with different views for building and manipulating RDF graphs. 268 Figure 1. The Jena2 Architecture. From the Jena system architecture, it can be seen that on the one side, the data structure and data model can improve data security; on the other hand, Graph Layer can be extended based on different applications views. RDF File, RDF Graph and RDF Triple RDF files, RDF graphs, and RDF triple are three different representations of the same knowledge. RDF files can be created by plain text file editors(such as Notepad) or by programs, the following are the textual contents of the ynu-lnic-3.rdf. //ynu-lnic-3.rdf <rdf:RDF xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns# xmlns:vCard="http://www.w3.org/2001/vcard-rdf/3.0#"> <rdf:Description rdf:about="http://www.lnic.ynu.edu.cn/Yang xiabai/"> <vCard:FN>Yang xiabai</vCard:FN> <vCard:N rdf:parseType="Resource"> <vCard:Family>xiabai</vCard:Family> <vCard:Given>Yang</vCard:Given> </vCard:N> </rdf:Description> </rdf:RDF> RDF files and RDF graph can be converted between each other. Figure 2 is an RDF diagram corresponding to the ynu-lnic-3.rdf file, and Figure 3 is an RDF diagram corresponding to the ynu-lnic-4.rdf file. In each figure, an ellipse represents a resource, and if empty, it is called an empty node. A directed edge represents a property corresponding to the resource, and a square represents the value corresponding to the attribute. Figure 2. The RDF graph of ynu-lnic-3.rdf. Figure 3. The RDF graph of ynu-lnic-4.rdf. RDF Triple is another representation of an RDF graph. The results of the ynu-lnic-3.rdf file 269 converted to a triple are shown below, where the first two lines are name spaces, the four numbers represent four Triple, and genid: ARP105295, ARP287553 stands for Empty nodes. //ynu-lnic-3.rdf <xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:vCard="http://www.w3.org/2001/vcard-rdf/3.0#"> 1 http://www.lnic.ynu.edu.cn/Yangxiabai/ subject http://www.w3.org/2001/vcard-rdf/3.0#FN predicate "Yang xiabai" object 2 genid:ARP105295 http://www.w3.org/2001/vcard-rdf/3.0#Family "xiabai" 3 genid:ARP105295 http://www.w3.org/2001/vcard-rdf/3.0#Given "Yang" 4 http://www.lnic.ynu.edu.cn/Yangxiabai/ http://www.w3.org/2001/vcard-rdf/3.0#N genid:ARP105295 Two RDF Files in Union, Intersection, Difference Operations The union operation is to combine the Triple of two RDF files into a redundant RDF file. After an RDF file is converted into an RDF directed graph, each side of the RDF directed graph is a statement. A statement contains three parts: subject, predicate and object, so the statement is also called a Triple. An RDF directed graph contains a series of statements that can be viewed as a set of statements, so repeated statements can be combined in one diagram. Merging two RDF files is actually the process of merging the Triple contained in the two graphs. Figure 4 shows the combined result of the ynu-lnic-3.rdf file and the ynu-lnic-4.rdf file. Figure 4. Union graph between ynu-lnic-3.rdf with ynu-lnic-4. RDF. The Intersection operation is to intersect the Triples that correspond to two RDF files, that is, the intersection of statements contained in the two figures. First, two RDF files are loaded into two models respectively, and then sizes of the two images in the model are evaluated. Each statement of the small image is listed by the Iterator, and compared with each statement in the large image. If the statement in the small image is included in the larger image, the statement in the small image is loaded into the third new model. The above comparison process is repeated until all the statements are compared. Then, the third model is the intersection of two RDF files. Figure 5 is the result of intersection of ynu-lnic-3.rdf file and ynu-lnic-4.rdf file. Figure 5. Intersection graph between ynu-lnic-3.rdf with ynu-lnic-4. RDF. 270 The Difference operation is to take the difference between the statements contained in the two RDF files, that is, the difference between the two sets of Triples. First, two RDF files are loaded into two models respectively. Each statement in the first image is listed by the Iterator, and compared with each statement in the second image. If the first graph Is not included in the second graph, the statement in the first figure is loaded into the third model. The above comparison process is repeated until all the statements are compared. Then the third model is the difference between two RDF files. The result of the difference set is dependent on which file is used as the first for the comprison. In this case, ynu-lnic-3.rdf is the first graph, and ynu-lnic-4.rdf is the second. Figure 6 is their difference. Figure 6. Difference graph between ynu-lnic-3.rdf with ynu-lnic-4. RDF. Design and Implementation of Knowledge Convergence Based on Jena The open source of the Jena system includes a total of 11 packages: jena.jar, xercesImpl.jar, xml-apis.jar, icu4j.jar, concurrent.jar, jakarta-oro-2.0.5.jar, antlr.jar, junit.jar, commons-logging. jar, log4j-1.2.7.jar, rdf-api-2001-01-19.jar. The major package used in this paper is jena.jar. To prepare the development environment, install Java sdk1.4.0 and Jcreator Pro250, add the 11 jar packages(under Lib in Jena system) to Jcreator Pro250 development environment. Then one can use Java design knowledge to integrate the user interface and code writing. Figure 7. A Visual Interface design and difference preview. The design of knowledge convergence interface is shown in Figure 7, the entire interface design includes three parts: upper, middle and bottom. The upper part and the middle part have the same 271 design. Both are composed of a command button and a textbox. The command button is responsible for selecting an RDF file from the "Open File Dialog"; the text box is for displaying the files opened with the command button. Thus, two RDF files are opened separately and displayed in two textboxes. The third part contains a textbox and six command buttons. The union preview button is responsible for implementing the Union operation of knowledge convergence, and displaying the result in a textbox.