Web of documents vs. Web of data

Web of Document: 数据之间关联少
Analogy: a global filesystem
Primary objects: documents
Links between: documents (or sub-parts of)
Degree of structure in objects: fairly low
Semantics of content and links: implicit
Designed for: human consumption

Web of Data
Analogy: a global database
Primary objects: things (or descriptions of things)
Links between: things (including documents)
Degree of structure in objects: high
Semantics of content and links: explicit
Designed for: machines first, humans later

键连数据 (Linked data)

定义: A method of publishing structured data so that it can be
interlinked and become more useful

键连资料是语义网的主题之一，描述了通过可链接的URI方式来发布、分享、连接Web中各类资源的方法。是一系列利用Web 在不同数据源之间创建语义关联的方法。

Web technologies: HTTP,URIs,RDF to share information processed automatically by computers

Linked Data Principles

1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names
3. When someone looks up a URI, provide useful RDF information
4. Include RDF statements that link to other URIs so that they can discover more things

存在问题

• Different URIs For the Same Thing
• Timeliness （not up to date）
• Provenance
• Tools

Linked data 评级

Semantic Web

核心:通过给万维网上的文档添加能够被计算机所理解的语义，从而使整个互联网成为一个通用的信息交换介质

Web中的Thing与Document

Web document

定义: A Web document is defined as something that has a URI and can return representations (responses in a format such as HTML or JPEG or RDF) of the identified resource in response to HTTP requests.

An HTML document is not a representation of a person. It is a representation of a Web document.

内容协商(Content Negotiation)

定义: 超文本传输协议中定义的一个机制，它使同一个统一资源标志符上的文档可以根据用户代理中指定的适用信息提供不同的版本

Web Thing

We use need different URIs for Things and Web documents
这里的Thing其实也就是知识图谱中的entity

从这个例子中也可以发现，某一个实体的web document可以是该实体的一个属性

303 重定向

解决问题: two documents don’t contain the same content

三个URI关系

<http://ex.com/id/alice>
  foaf:page <http://ex.com/people/alice> ; 
  rdfs:isDefinedBy <http://ex.com/data/alice> ;
  a foaf:Person ;
  foaf:name "Alice” ;
  foaf:mbox <mailto:alice@example.com> ; ...