Editing Semantic Web (section)

== Background ==
{{Further|Semantic network#History}}
The concept of the [[semantic network]] model was formed in the early 1960s by researchers such as the [[Cognitive science|cognitive scientist]] [[Allan M. Collins]], [[Linguistics|linguist]] [[Ross Quillian]] and [[psychologist]] [[Elizabeth F. Loftus]] as a form to represent semantically structured knowledge. When applied in the context of the modern internet, it extends the network of [[hyperlink]]ed human-readable [[web pages]] by inserting machine-readable metadata about pages and how they are related to each other.  This enables [[Web crawler|automated agents]] to access the Web more intelligently and perform more tasks on behalf of users. The term "Semantic Web" was coined by [[Tim Berners-Lee]],<ref name="Berners-Lee"/> the inventor of the World Wide Web and director of the World Wide Web Consortium ("[[W3C]]"), which oversees the development of proposed Semantic Web standards. He defines the Semantic Web as "a web of data that can be processed directly and indirectly by machines".

Many of the technologies proposed by the W3C already existed before they were positioned under the W3C umbrella. These are used in various contexts, particularly those dealing with information that encompasses a limited and defined domain, and where sharing data is a common necessity, such as scientific research or data exchange among businesses. In addition, other technologies with similar goals have emerged, such as [[microformat]]s.

=== Limitations of HTML ===
Many files on a typical computer can be loosely divided into either human-readable documents, or machine-readable data. Examples of human-readable document files are mail messages, reports, and brochures. Examples of machine-readable data files are calendars, address books, playlists, and spreadsheets, which are presented to a user using an application program that lets the files be viewed, searched, and combined.

Currently, the World Wide Web is based mainly on documents written in [[Hypertext Markup Language]] (HTML), a markup convention that is used for coding a body of text interspersed with multimedia objects such as images and interactive forms. Metadata tags provide a method by which computers can categorize the content of web pages. In the examples below, the field names "keywords", "description" and "author" are assigned values such as "computing", and "cheap widgets for sale" and "John Doe".

<syntaxhighlight lang="html">
<meta name="keywords" content="computing, computer studies, computer" />
<meta name="description" content="Cheap widgets for sale" />
<meta name="author" content="John Doe" />
</syntaxhighlight>

Because of this metadata tagging and categorization, other computer systems that want to access and share this data can easily identify the relevant values.

With HTML and a tool to render it (perhaps [[web browser]] software, perhaps another [[user agent]]), one can create and present a page that lists items for sale. The HTML of this catalog page can make simple, document-level assertions such as "this document's title is 'Widget Superstore{{'"}}, but there is no capability within the HTML itself to assert unambiguously that, for example, item number X586172 is an Acme Gizmo with a retail price of €199, or that it is a consumer product. Rather, HTML can only say that the span of text "X586172" is something that should be positioned near "Acme Gizmo" and "€199", etc. There is no way to say "this is a catalog" or even to establish that "Acme Gizmo" is a kind of title or that "€199" is a price. There is also no way to express that these pieces of information are bound together in describing a discrete item, distinct from other items perhaps listed on the page.

[[Semantic HTML]] refers to the traditional HTML practice of markup following intention, rather than specifying layout details directly. For example, the use of {{tag|em|o}} denoting "emphasis" rather than {{tag|i|o}}, which specifies [[italics]]. Layout details are left up to the browser, in combination with [[Cascading Style Sheets]]. But this practice falls short of specifying the semantics of objects such as items for sale or prices.

Microformats extend HTML syntax to create [[Machine-readable data|machine-readable]] semantic markup about objects including people, organizations, events and products.<ref>{{cite book |last=Allsopp |first=John |title=Microformats: Empowering Your Markup for Web 2.0 |date=March 2007 |publisher=[[Apress|Friends of ED]] |isbn=978-1-59059-814-6 |page=[https://archive.org/details/isbn_9781590598146/page/368 368] |url-access=registration |url=https://archive.org/details/isbn_9781590598146/page/368 }}</ref> Similar initiatives include [[RDFa]], [[Microdata (HTML)|Microdata]] and [[Schema.org]].

=== Semantic Web solutions ===
The Semantic Web takes the solution further. It involves publishing in languages specifically designed for data: [[Resource Description Framework]] (RDF), [[Web Ontology Language]] (OWL), and Extensible Markup Language ([[XML]]). HTML describes documents and the links between them. RDF, OWL, and XML, by contrast, can describe arbitrary things such as people, meetings, or airplane parts.

These technologies are combined in order to provide descriptions that supplement or replace the content of Web documents. Thus, content may manifest itself as descriptive data stored in Web-accessible [[database]]s,<ref>Artem Chebotko and Shiyong Lu, "Querying the Semantic Web: An Efficient Approach Using Relational Databases", [[LAP Lambert Academic Publishing]], {{ISBN|978-3-8383-0264-5}}, 2009.</ref> or as markup within documents (particularly, in Extensible HTML ([[XHTML]]) interspersed with XML, or, more often, purely in XML, with layout or rendering cues stored separately). The machine-readable descriptions enable content managers to add meaning to the content, i.e., to describe the structure of the knowledge we have about that content. In this way, a machine can process knowledge itself, instead of text, using processes similar to human [[deductive reasoning]] and [[inference]], thereby obtaining more meaningful results and helping computers to perform automated information gathering and research.

An example of a tag that would be used in a non-semantic web page:
<syntaxhighlight lang="xml">
<item>blog</item>
</syntaxhighlight>

Encoding similar information in a semantic web page might look like this:
<syntaxhighlight lang="xml">
<item rdf:about="https://example.org/semantic-web/">Semantic Web</item>
</syntaxhighlight>

Tim Berners-Lee calls the resulting network of [[Linked Data]] the [[Giant Global Graph]], in contrast to the HTML-based World Wide Web. Berners-Lee posits that if the past was document sharing, the future is [[data sharing]]. His answer to the question of "how" provides three points of instruction. One, a URL should point to the data. Two, anyone accessing the URL should get data back. Three, relationships in the data should point to additional URLs with data.

==== Tags and identifiers ====
[[Tag (metadata)|Tag]]s, including hierarchical categories and tags that are collaboratively added and maintained (e.g. with [[folksonomy|folksonomies]]) can be considered part of, of potential use to or a step towards the semantic Web vision.<ref>{{cite web |title=Towards the Semantic Web: Collaborative Tag Suggestions |url=https://www.ambuehler.ethz.ch/CDstore/www2006/www.rawsugar.com/www2006/13.pdf}}</ref><ref>{{cite book |last1=Specia |first1=Lucia |last2=Motta |first2=Enrico |title=The Semantic Web: Research and Applications |chapter=Integrating Folksonomies with the Semantic Web |series=Lecture Notes in Computer Science |date=2007 |volume=4519 |pages=624–639 |doi=10.1007/978-3-540-72667-8_44 |publisher=Springer |isbn=978-3-540-72666-1 |language=en|doi-access=free }}</ref><ref>{{cite web |title=Bridging the gap between folksonomies and the semantic web: an experience report |url=http://oro.open.ac.uk/23608/4/semnet2007.pdf}}</ref>

Unique [[identifier]]s, including hierarchical categories and collaboratively added ones, analysis tools and [[metadata]], including tags, can be used to create forms of semantic webs – webs that are to a certain degree semantic<!-- (often also available on the Web)-->.<ref>{{cite journal |last1=Nicholson |first1=Josh M. |last2=Mordaunt |first2=Milo |last3=Lopez |first3=Patrice |last4=Uppala |first4=Ashish |last5=Rosati |first5=Domenic |last6=Rodrigues |first6=Neves P. |last7=Grabitz |first7=Peter |last8=Rife |first8=Sean C. |title=scite: A smart citation index that displays the context of citations and classifies their intent using deep learning |journal=Quantitative Science Studies |date=5 November 2021 |volume=2 |issue=3 |pages=882–898 |doi=10.1162/qss_a_00146|doi-access=free }}</ref>  In particular, such has been used for structuring scientific research i.a. by research topics and [[branches of science|scientific fields]] by the projects [[OpenAlex]],<ref>{{cite news |last1=Singh Chawla |first1=Dalmeet |title=Massive open index of scholarly papers launches |url=https://www.nature.com/articles/d41586-022-00138-y |access-date=14 February 2022 |journal=[[Nature (journal)|Nature]] |date=24 January 2022 |language=en |doi=10.1038/d41586-022-00138-y}}</ref><ref>{{cite news |title=OpenAlex: The Promising Alternative to Microsoft Academic Graph |url=https://library.smu.edu.sg/topics-insights/openalex-promising-alternative-microsoft-academic-graph |access-date=14 February 2022 |work=Singapore Management University (SMU) |language=en}}</ref><ref>{{cite web |title=OpenAlex Documentation |url=https://docs.openalex.org/ |access-date=18 February 2022}}</ref> [[Wikidata]] and [[Scholia]] which are under development and provide [[API]]s, Web-pages, feeds and graphs for various [[Semantic query|semantic queries]].

=== Web 3.0<!--'Web 3.0' redirects here--> ===
Tim Berners-Lee has described the Semantic Web as a component of Web 3.0.<ref>{{cite news
 | url=https://www.nytimes.com/2006/05/23/technology/23iht-web.html
 | title=A 'more revolutionary' Web
 | date=23 May 2006
 | last=Shannon |first=Victoria 
 | access-date=26 June 2006
 | work=[[International Herald Tribune]]}}</ref>

{{blockquote|People keep asking what Web 3.0 is. I think maybe when you've got an overlay of [[scalable vector graphics]] – everything rippling and folding and looking misty&nbsp;– on [[Web 2.0]] and access to a semantic Web integrated across a huge space of data, you'll have access to an unbelievable data resource …|Tim Berners-Lee, 2006}}

"Semantic Web" is sometimes used as a synonym for "Web 3.0",<ref>{{Cite web |title=Web 3.0 Explained, Plus the History of Web 1.0 and 2.0 |url=https://www.investopedia.com/web-20-web-30-5208698 |access-date=2022-10-21 |website=Investopedia |language=en}}</ref> though the definition of each term varies.

===Beyond Web 3.0===
The next generation of the Web is often termed Web 4.0, but its definition is not clear. According to some sources, it is a Web that involves [[artificial intelligence]],<ref>{{Cite web | title=Archived copy | url=https://www.rsisinternational.org/IJRSI/Issue31/75-78.pdf | archive-url=https://web.archive.org/web/20180508104833/http://rsisinternational.org:80/IJRSI/Issue31/75-78.pdf | archive-date=2018-05-08}}</ref> the [[internet of things]], [[pervasive computing]], [[ubiquitous computing]] and the [[Web of Things]] among other concepts.<ref>Almeida, F. (2017). Concept and dimensions of web 4.0. International journal of computers and technology, 16(7).</ref> According to the European Union, Web 4.0 is "the expected fourth generation of the World Wide Web. Using advanced artificial and ambient intelligence, the internet of things, trusted blockchain transactions, virtual worlds and XR capabilities, digital and real objects and environments are fully integrated and communicate with each other, enabling truly intuitive, immersive experiences, seamlessly blending the physical and digital worlds".<ref>{{cite web | url=https://www.politico.eu/article/the-commission-wants-the-eu-to-lead-in-web-4-0-come-again/ | title=The Commission wants the EU to lead on 'Web 4.0' — whatever that is | date=11 July 2023 }}</ref>