Associate data entry-RDF Application

Introduction
A Semantic Web is a data network that allows data to be shared, not just bound by applications.
However, semantic networks not only put data on the Internet, but also try to connect the data and generate the connection between the data and the real thing, so that people and machines can read and understand the data.

The Semantic Web isn't just about putting data on the web. It is about making links, so that a person or machine can have e the web of data.

-- Linked Data Design Issues. Tim Berners-Lee
Linked Data is the first feasible Semantic Network expression. It uses the RDF Data model and uses URI (unified resource identifier) to name Data entities, to publish and deploy instance data and class data, so that the data can be revealed and obtained through the HTTP protocol, and emphasize the Data Association, mutual connection, and context information beneficial to human-machine understanding.

Linked data is a set of best practices for publishing and deploying instance and class data using the RDF data model, and uses uniform resource identifiers (URIs) to name the data objects. the approach exposes the data for access via the HTTP protocol, while emphasizing data interconnections, interrelationships and context useful to both humans and machine agents.

-- Linked Data FAQ. M. K. Bergman
Semantic Network is a huge project with various difficulties, making it a long-term goal and vision. Relational Data is a kind of practical activity, which is feasible and practical, it has become an optimal and feasible solution for implementing semantic networks.

Features of RDF

Resource Description Framework, a derivative version of XML (Extensible Markup Language), is the basic data model of associated data. Tim Berners-Lee faced the following two problems when designing it:

• How can we design a language that is easy to learn, easy to disseminate, and suitable for standardization?
• How to Design the entry and exit of discrete data?
To solve these two problems, RDF has the following features:

• Use XML as the basic language
• Use URIs as the name of a real thing
• Use HTTP URIs to let people know how to search for data in the network by name (that is, create a discrete data entry)
• Include connections with other URIs so that people can find more useful things (that is, creating discrete data outlets)
• Triples are used to store data.
In fact, some RDF versions do not use the XML language, but mainly refer to the initial version.

A simple RDF example Copy codeThe Code is as follows: <? Xml version = "1.0"?>
<Rdf: RDF xmlns: rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns"
Xmlns: dc = "http://purl.org/dc/elements/1.1/">
<Rdf: Description rdf: about = "http://www.w3.org/">
<Dc: title> World Wide Web Consortium </dc: title>
</Rdf: Description>
</Rdf: RDF>

The following list is displayed when you use the W3C RDF authentication service for the RDF example:
Triples of the Data Model

Number	Subject	Predicate	Object
1	Http://www.w3.org/	Http://purl.org/dc/elements/1.1/title	"World Wide Web Consortium"

What is this?

Triples are the basic representations of the RDF data model. The so-called triple is: the primary (Subject)-That (Predicate)-Object ).

A triple store is designed to store and retrieve identities that are constructed from triplex collections of strings (sequences of letters ). these triplex collections represent a subject-predicate-object relationship that more or less corresponds to the definition put forth by the RDF standard.

-- Triple Store. Jack Rusher
Different from relational data, the data itself does not have a huge Link (this is not feasible in the face of such a large data network), but uses statements similar to human statements (Statement) for example:

• Tom is a man. (Tom is a man)
• Tom lives in a red house. (Tom lives in a red house)
• Tom married with Lili. (Tom and Lili are married)
It can be seen that the triple form also has powerful data storage and expression potential, and humans are long-term beneficiaries of this form. Of course, the expressions above are friendly to humans, but not very friendly to machines, because such predicates have no good limits on the object, at least the machine does not think so. Therefore, we should write this pattern:

• Tom sex man (male)
• Tom house red)
• Tom (Tom) wife (wife) Lili (Lili)
Back to the title. What is this? It expresses the following content:

1. http://www.w3.org (indicating what the subject of the statement is, because http uri maps real things, so it can be seen as a description of what real things)
2. http://purl.org/dc/elements/1.1/title (attributes of the subject, which generally represent the type of the object, for example, dc: title is used to indicate the name of the resource in the Dublin Core, that is, the object is a name of the resource)
3. World Wide Web Consortium (object)

How do others obtain RDF?

This process is described as follows:

• First, request the http uri.
• Generally, the HTTP request headers of browsers are text/html and application/xhtml + xml. Therefore, the server returns common html/xhtml documents.
• For semantic browsers, the HTTP request header is of the application/rdf + xml type. Therefore, the server performs 303 redirection to obtain the corresponding RDF file.
That is to say, for an http uri, two expressions can be returned: document and data. In this way, two different networks are established, one for human reading and the other for machine reading.