Introduction to the Semantic Web
Towards the Semantic Web
Introduction to Linked Data
What is Linked Data
The Many Names of the Semantic Web
Semantic Web Misconceptions
At various points in time and in various contexts, the Semantic Web has been referred to as the Linked Data Web, the Web of Data, Web 3.0, the Enterprise Information Web, and even the Giant Global Graph.
On the surface, all of these names are for the same thing. They all refer to the family of technology standards from the World Wide Web Consortium (W3C) that are designed to describe and relate data both on the Web and inside enterprises. However, many layers of meaning lie beneath most of these names.
After completing this lesson, you will know:
Three terms that have been traditionally used to refer to Semantic Web technologies, and which one is the most widely accepted.
A brief history of the evolution of each of these three terms.
A few reasons why each of these terms might be appropriate to use in certain situations and circumstances.
Today's Lesson
Let's take a closer look at a few of the most common names for these standards.
Semantic Web is the closest thing we have to an official name for these technologies. Tim Berners-Lee first used the term in 1999 to describe the vision of machine-processable data on the Web, and today it is also the official name of the umbrella of W3C activity that is responsible for all of the relevant technology standards.
Although Semantic Web is a term that has often been criticized as confusing, opaque, and academic, it does nonetheless capture two of the most important aspects of these technologies:
Semantic: The meaning of the data is not only explicitly represented and richly expressive, but it also "travels" along with the data itself.
Web: Individual pieces of data are linked together into a network of information, just as documents are linked together on the World Wide Web.
"Semantic Web" is still the term most commonly used by professionals working in the field. It is also the term most often seen in the names of conferences, books, mailing lists, and websites. It has been in use for over 12 years, and it is unlikely to disappear any time soon. As an editorial policy, Semantic University always uses the term Semantic Web when speaking about these technologies.
One slight wrinkle arises when using the term Semantic Web, however. While the term is often used to speak of the core Semantic Web technology standards, it is also used (usually when preceded with the definite article the) to refer to the overall vision of annotating the World Wide Web with explicit data. This is the description of the Semantic Web as given in Tim Berners-Lee, Jim Hendler, and Ora Lasilla's 2001 Scientific American article, which lays out a future in which personalized software agents consume personal and public data on the Web in an attempt to automate many aspects of our lives.
When used in this sense, the Semantic Web refers to a long-term, ongoing endeavor to progress the Web towards this vision; this undertaking is multi-faceted and involves efforts on many fronts, including research, standards development, education, software development, commercialization, evangelism, and public policy.
Countless professionals in academia, the W3C, governments, and industry are working towards realizing the vision of the Semantic Web. At the same time, many people are using Semantic Web technologies for domain-specific Web applications and enterprise solutions that are unrelated to the Semantic Web vision, except by virtue of their involving the same family of technologies.
Seven years after introducing the term Semantic Web, Tim Berners-Lee gave us a new term: Linked Data. This was originally the name for a specific set of best practices for using Semantic Web technologies to publish data on the Web. These best practices emphasized creating links between different data sets and making the links between data items easy to follow without the need for any software other than a standard Web browser.
Since its introduction in 2006, the term Linked Data has evolved in several ways. It is still used to refer to Tim Berners-Lee's four rules for publishing data on the Web, though that usage is now often made explicit by referring to Linked Data principles. However, Linked Data has also come to be seen as a clearer, simpler alternative to Semantic Web and is now often used as a general name when talking about Semantic Web technologies. When used in this way, Linked Data tends to emphasize the "Web" part of "Semantic Web" and deemphasize the "Semantic" parts. People who speak about building software with Linked Data are likely to be using RDF and SPARQL and are less likely to be using significant RDF Schema or OWL.
The concept of Linked Data also evolved into a successful worldwide project to begin publishing data on the Web. In 2007, the W3C Semantic Web Education and Outreach group founded the Linked Open Data project. This project expands on the ideas of Linked Data by encouraging people and organizations to publish data openly on the Web.
Because of the similarity between the terms Linked Data and Linked Open Data, you may find that people sometimes assume that using Linked Data technologies (or Semantic Web technologies, for that matter) requires that the information being represented be made publicly available. This is not the case, however, and it is important to make clear the distinction between explicitly representing information in a machine-processable manner (i.e., in the Semantic Web or via Linked Data) and publishing data sets on the Web for public consumption (i.e., Linked Open Data). Many enterprises are using Linked Data internally without ever exposing any of their data on the Web.
Web 3.0 is probably the most nebulous and controversial of the terms used to refer to the Semantic Web. Following the explosive popularity and success of Web 2.0 as a term to represent the evolution of the Web towards social networking, crowdsourcing, and user-generated content, many people have attempted to corner the market on the meaning of the obvious next step, Web 3.0. The use of Web 3.0 as a moniker for Semantic Web is probably the most well-known of these attempts.
Although the use of the term Web 3.0 for Semantic Web is often mocked as little more than marketing hype, the name can in truth be used to convey a sense of the natural evolution of the Web.
In the mid-1990s, the burgeoning Web 1.0 was largely a read-only Web; a small number of content producers published websites to be consumed by a much larger number of users.
Web 2.0 flourished in the early-to-mid 2000s, transforming the static document-based Web into a dynamic and interactive social space.
If we view Web 2.0, then, as an evolution of the Web linking together not only documents but also people, then Web 3.0 might be considered a further evolution of the Web to link together not only documents but also data.
As if the confusion between these terms were not enough, this is not even close to the end of the story. People have been working with semantic technologies since long before the first Semantic Web technology was ever conceived. So what is the relationship between semantic technologies and the Semantic Web? More on that in future lessons.