Linked Open Data: Overview, Usage and Applications boxuan li Abstract—Since 2006 the linked data was put forward first, five On these different computer, he wants to find some data, he has years have been past. The linked data have a great development. to connected to some new machines, running a new programs, This article proceeds with the Linked Data, introduces what is the in order to find some information from the new data format. Linked Data, and what can I do with Linked Data.And then the article describes the relation between semantic web and Linked These are not compatible, that is very frustrating! Actually in Data, the structure of semantic web,some of the technologies of the computers there are only files. If you can think them as which can be used by Linked Data.After this, the article describes some parts of a large virtual system, such as internet, that’s the four principles of Linked data, the advantages of Linked will be easy! data, the technologies of Linked data. In the followed chapter, the article shows how to publish Linked data in the web. The Internet originally was designed to put many documents fourth chapter is about the application of Linked data. Finally, together. But now you can put your data on the internet. Data the article shows the challenges of Linked data, and then gives and document is different. You can read the document, only the summary. read, or click the link in the document. But you can use many Keywords: semantic web, linked data, RDF, URI data with a computer. And now we can think about it, if the people form all over the world put all data on the internet, I. Introduction and then we make some rules to define them and unify their Tim Berners-Lee, who is the initiator of the World Wide format. What will happen? For the each datum, no matter what Web, divides the process of developing of World Wide Web it is, as long as there are people, who look for the relation into two phases.In the first phase, World Wide Web should be among data, they can focus on all the data,and connect them. a powerful tool, which is useful for the cooperation among The most important is, associated with more data, the data are humans. In the first ten years World Wide Web achieves the more valuable. This is the linked data. goal: it provides lots of information as HTML to humans In a word, linked data can be considered as a set. The set and with these information the cooperation among humans uses the RDF data model, uses URI to name the entity. It is much more than before and the life of human is changed. publishs and deploys the instance data and class data, and In the second phase, the cooperation should be extended to through the HTTP protocol to access the data. At the same the machines[1]. The machines should analyze all data on time, the set emphasizes the connection of the data[22][23]. the Internet, including the content and links, and the human can cooperate with machines. That means the machines can understand the content or the concept of data, and then the B. What can I do with linked data? machines can execute the some operation such as finding or analysing. On the other hand, because our world consists of With Linked data, man can find so many information step all kinds of data. So, in this phase, every book has a separate by step in the internet. For example, Bob has a friend called website; every author has a record, which can be accessed Kim. Kim has his identifier in internet. Bob click the link of openly; every publication, publisher, key-word......even every Kim’s identifier. And then he will get many information of knowledge point has a unique identifier in the network. People Kim, such as: Kim’s friends, the city where Kim lives now, can find the detailed description about all of the relationship the club that Kim has joined in and so on. If Bob is interested among these resources in the address, which is led to by the in Kim’s friends, he can click the link of Kim’s friends, and identifier. Even all of the things in the world have identifiers. then Kim’s friends list will be showed to Bob, or if Bob is There are relationship among these things, and the computer interested in the Kim’s club, he can click the link of the club, can analyse and find the knowledge in the network automati- and then Bob can get the introduction about the club. This cally. This is an orderly world of Knowledge, and this is the is only a small example in the normal life. Actually linked world of Linked data[2]. data has many application in many aspects in our life. I will mention them in the Chapter four. A. What is Linked data? In the next chapter, i will introduce the semantic web, the Before we talk about the linked data, we’ll see an example. relation between semantic web and linked data, and the detail If Bob is a software engineer, working in a large laboratories. of linked data. In the third chapter, i will introduce how does So many people come here from all over the world. Their the linked data work. In the fourth chapter i will write some computers are different, the data format are different, and the applications of linked data. At the end of the paper i will give file system is also different. If Bob wants to build something. my conclusion. II. Overview URL(Uniform Resource Locator), URN(Uniform Resource In this chapter I will introduce the main technology of Name) is that, URI refers to all the resources identified by Linked data. But before this, i must mention semantic web. In the string on the internet, and URI contains URL and URN. the introduction, i have said, in semantic web, the cooperation In addition the semantic web wants to establish a network should be extended to the machines. That means the machines of the global information, this network should contain all can understand the content or the concept of data, and then the the resources about all the language and characters. So, the machines can execute the some operation such as finding or semantic web uses the Unicode as the the coding scheme of analysing. Linked data can be seen as a method to publish character. This layer is the basis of semantic web. It can locate resources on the web. Fortunately this method use some the resources on the web, and unifies the coding scheme of ff technologies of semantic web. In addition, the formats of some characters in di erent regions[39]. published resources are the same, and they can be understood The second layer is XML layer. The XML layer is the by computer and this is the basis of the interaction among grammatical layer. In this layer, the users can defined some the computers. In other words, the linked data is a method to tags to identify the published content, and use (Document Type achieve the semantic web. So, in order to understand linked Definition DTD)or XML Schema to limit the structure of the data better, we must know the semantic web first. tag[4][5][6][7].Because the XML tag can be made by users, it is possible that, some tags have same name. In order to A. The key technology of semantic web. avoid the situation, W3C use the NameSpace technology.For example, the user can make <author> tag: <k:author xmlns:k=http://foo.bar.com/xml/customer/dtd>. It shows that, the tag<author> is in the NameSpace of K: http://foo.bar.com/xml/customer/dtd. So, if other people make the same tag<author>, as long as the NameSpaces are differ- ent, the tags are also different. Because of this character of XML, the structure of document can be described. It should be noted that, people can understand the tag <author>, but the computer doesn’t know the meaning of the tag. That means, the XML is the format of data exchange. XML can solve the problem about the order and the structure of the document, but it can’t deal with the semantic and the connection of the document. How to allow the computer to understand the meaning of the tag, this is the task of the third layer. The third layer is RDF(Resource Description Framework, RDF) and RDF schema layer. RDF is a opened Meta data Framework[8][9][10][40][43].RDF doesn’t describe the se- mantic, but it provides an ability, that the semantic can be described. The Meta data Framework defines a data model, which can be understood by computer. Man can use the data model to describe the semantic. This data model contains three kinds of object: 1) The resource: maybe a webpage, or part of webpage, or an object that can’t be accessed through web. Fig. 1. the structure of semantic web 2) The property: it describes the character, attribute or the There are seven layers in the semantic web model of Tim- relation of resources Berners-Lee. And the second, third and fourth are the key 3) The statement: it contains the resource, the name of the layers of the semantic web. These layers describe the semantic property of the resource, and the value of the property.