Metadata and the Semantic Web - Web Standards: Mastering HTML5, CSS3, and XML - page 231

To browsers, web documents consisted of human-readable data only. In fact, information was confused with the
containers that contained them. In contrast to the conventional Web (the “Web of documents”), the Semantic Web is
the “Web of data” [1]. The Semantic Web provides machine-processable data, making it possible for software agents
to “understand” the meaning of information (in other words, semantics) presented by web documents. This feature
can be used for a variety of services [2], such as museums [3], community sites [4], podcasting [5], Big Data processing,
and search engines.

■ the word semantic is used on the Web in other contexts as well. For example, in htML5 there are semantic
(in other words, meaningful) structuring elements, but this expression refers to the “meaning” of elements. in this context,
the word semantic contrasts the “meaning” of elements, such as that of section (a thematic grouping), with the generic
elements of older htML versions, such as the “meaningless” div . the semantics of markup elements should not be
confused with the semantics (in other words, machine-processability) of metadata annotations and web ontologies used
on the Semantic Web. the latter can provide far more sophisticated data than the meaning of a markup element.

Caution

Conventional web documents can be extended with additional data that add meaning to them rather than
structure alone. Semantic Web is a new approach that is going to change the world of the Web. Surprisingly, Tim
Berners-Lee described the reason for the existence of the Semantic Web as early as 2001 [6]. On the Semantic Web,
data can be retrieved from seemingly unrelated fields automatically in order to combine them, find relations, and
make discoveries [7]. The machine-processability can also be used in huge and complex datasets that are considered
Big Data .
The Semantic Web should be considered an extension of the conventional Web [8]. Web 2.0 is an umbrella term
used for a collection of technologies that form the second generation of the Web, such as Extensible Markup Language
(XML), Asynchronous JavaScript and XML (Ajax), Really Simple Syndication (RSS), and Session Initiation Protocol
(SIP). They are the underlying technologies and standards behind instant messaging, Voice over IP, wikis, blogs,
forums, and web syndication.
The next generation of web services is denoted as Web 3.0 , which is an umbrella term usually referring to
customization and semantic contents and more sophisticated web applications toward artificial intelligence,
including computer-generated contents [9].
The Semantic Web is a major aspect of Web 2.0 [10] and Web 3.0 [11]. Web 3.0 can be considered a superset of the
Semantic Web that features social connections and personalization.
Several technologies contribute to the sharing of such information instead of web pages alone, and the number
of Semantic Web applications is constantly increasing.
All data controlled by conventional web applications are kept by the applications themselves, making a significant
share of data and their relationships virtually unavailable for automated processing. Semantic Web applications,
on the other hand, can access this data through the general web architecture and transfer structured data between
applications and web sites [12]. Semantic web technologies can be widely applied in a variety of areas, such as
data integration, resource discovery and classification, cataloging, intelligent software agents, content rating, and
intellectual property right descriptions [13]. A much wider range of tasks can be performed on semantic web pages than
on conventional ones; for example, relationships between data and even sentences can be automatically processed
(see the next sections). Additionally, the efficiency is much higher. For example, a very promising approach provides
direct mapping of relational data to RDF, making it possible to share data of relational databases on the Semantic Web
[14]. Since relational databases are extremely popular in computing, databases that are publicly unavailable can now
be shared on the Semantic Web. Commercial RDF database software packages are already available on the market
(5Store, AllegroGraph, BigData, Oracle, OWLIM, Talis Platform, Virtuoso, and so on) [15]. Semantic tools can also be
used in a variety of other areas, including business process modeling or diagnostic applications [16].