Linked Data

1. Linked Data
 : how do we publish the Semantic Web Data?
 : what identifiers do we use?

https://en.wikipedia.org/wiki/Linked_data

http://linkeddata.org/


2. Semantic Web Principles
 - Anyone can make assertions about anything

 - Entities are referred to using Uniform Resource Identifiers
  1) a resource can be anything that has identity
  2) the resource is the conceptual mapping to an entity or set of entities, not necessarily the entity which corresponds to that mapping at any particular instance in time
  3) httpRange-14: "What is the range of the HTTP range dereference operation?"
   => HTTP URIs (without "#") should be understood as referring to documents, not cars
  4) Information Resource
   * resources, identified by URIs and whose essential characteristics can be conveyed in a message
   * If dereferencing the URI results in a 200 OK response code, the resource is an information resource
   * If it results in 303 See Other response, the resource could be any resource

 - Based on XML technologies

 - Formal semantics


3. The Linked Data Principles
 : Set of publishing practices for the Semantic Web data
 - Use URIs as names for things
  1) don't use bNodes, always give URIs as you can
  2) use a unique identifier to denote things

 - Use HTTP URIs so that people can look up those names
  1) enables "lookup" of URIs via Hypertext Transfer Protocol
  2) piggy-backs on hierarchical Domain Name System to guarantee uniqueness of identifiers
  3) connect logical level (thing) with physical level (source)

 - When someone looks up a URI, provide useful information
  1) when somebody looks up a URI, return data using the standards (RDF*, SPARQL)

 - Include links to other URIs, so that they can discover more things


4. Publishing Semantic Web Data
 - Defining RDF Vocabularies
  1) the Semantic Web Best Practice Recipes for Publishing RDF Vocabularies
   * distinguishes between 'hash' and 'slash' namespaces
   * uses content negotiation (HTTP Accept: header) to serve different representations of resources

 https://www.w3.org/TR/swbp-vocab-pub/


5. Cool URIs
 : URIs should be designed with three things in minds; simplicity, stability and manageability

https://www.w3.org/TR/cooluris/

https://www.w3.org/Provider/Style/URI