Digital Public HistoryLecture 4: Metadata, XML, and the Semantic Web

Jason M. Kelly, IUPUI

The Semantic Web

• syntax: how something is expressed

• semantics: meaning

The Semantic Web: The Problem

• HTML and the stricture of information

The Semantic Web: The Solution

• Linked Data

• e.g. Library of Congress Name Authority Filehttp://id.loc.gov/authorities/names.html

The Semantic Web: The Solution

• Linked Data

• e.g. Library of Congress Name Authority Filehttp://id.loc.gov/authorities/names.html

• Resource Description Framework (RDF)

• RDF Triple: Subject-Predicate-Object

From Clifford Tatum, “Web 2.0 and/or Semantic Web?,” Digital Scholarshi eHumanities Group Royal Netherlands Academy of Arts and Sciences (5 June 2011),

http://digital-scholarship.ehumanities.nl/epubs/web-2-0-andor-semantic-web/

“Through hyperlinking, documents, collections of documents, and related audio and visual resources are structured across the web (Halavais 2008, 43). In this bottom-up, nonhierarchical fashion, features of Web 2.0 facilitate co-construction of intertextual discourses. However, content structures emerging from Web 2.0 practices, such as hyperlinking, suffer from some basic linguistic limitations, such as homonyms and synonyms. (Vossen and Hagemann, 2007). In this way, the flexibility of Web 2.0 can also limit the precision of aggregated content.”

“The RDF triple is different from the hyperlink in two important ways. It defines object relationships through simple facts about kinds of objects within a particular domain and each part of the triple has a unique identifier or Uniform Resource Identifier (URI). In comparison, the hyperlink connects two objects and in the process the relationship is named in ways that are not always relevant to the meaning of the relationship. For example, a common link naming convention, such as: ‘you can find the report here,’ where the word here, does very little to give meaning to the link.

Additionally, the objects are connected by a hyperlink, which itself does not have a unique URI as such. Instead, the HTML code that defines a hyperlink is embedded in the local content and the code construction includes the URL for the linked-to object. The three distinct parts of the object relationship are identifiable within the local HTML code, but the hyperlink is not an entity separate from the two linked objects.”