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the semantic web a gide to the future of XML, Web Services and Knowledge Management - Daconta M,C.

Daconta M,C. the semantic web a gide to the future of XML, Web Services and Knowledge Management - Wiley publishing , 2003. - 304 p.
ISBN 0-471-43257-1
Download (direct link): thesemanticwebguideto2003.pdf
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The second key accomplishment is that XML provides a simple, standard syntax for encoding the meaning of data values, or meta data. An often-used definition of meta data is "data about data." We discuss the details of the XML syntax later. For now what is important is that XML standardizes a simple, text-based method for encoding meta data. In other words, XML provides a simple yet robust mechanism for encoding semantic information, or the meaning of data. Table 3.1 demonstrates the difference between meta data and data. It should be evident that the data is the raw context-specific values and the meta data denotes the meaning or purpose of those values.
The third major accomplishment of XML is standardizing a structure suitable to express semantic information for both documents and data fields (see the sidebar comparing them). The structure XML uses is a hierarchy or tree structure. A good common example of a tree structure is an individual's filesystem on a computer, as shown in Figure 3.3. The hierarchical structure allows the user to decompose a concept into its component parts in a recursive manner.
Table 3.1 Comparing Data to Meta Data
Joe Smith 222 Happy Lane Sierra Vista AZ
Name Address City State Zip code
Understanding XML and Its Impact on the Enterprise
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[ CH technical
( CH xml-magazine
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Folders Organization Chart
Figure 3.3 Sample trees as organization structures.
The last accomplishment of XML is that it is not a new technology. XML is a subset of the Standardized Generalized Markup Language (SGML) that was invented in 1969 by Dr. Charles Goldfarb, Ed Mosher, and Ray Lorie. So, the concepts for XML were devised over 30 years ago and continuously perfected, tested, and broadly implemented. In a nutshell, XML is "SGML for the Web." So, it should be clear that XML possesses some compelling and simple value propositions that continue to drive its adoption. Let's now examine the mechanics of those accomplishments.
The Difference between Documents and Data Fields
An electronic document is the electronic counterpart of a paper document.
As such, it is a combination of both content (raw information) and presentation instructions. Its content uses natural language in the form of sentences, paragraphs, and pages. In contrast, data fields are atomic name/value pairs processable by a computer and are often captured in forms.
Both types of information are widespread in organizations, and both have strengths and weaknesses. A significant strength of XML is that it enables meta data attachment (markup) on both of these data sources. Thus XML, bridges the gap between documents and data to enable them to both participate in a single web of information.
^32 |Chapter3
What Is XML?
Chapter 3
XML is not a language; it is actually a set of syntax rules for creating semantically rich markup languages in a particular domain. In other words, you apply XML to create new languages. Any language created via the rules of XML, like the Math Markup Language (MathML), is called an application of XML. A markup language's primary concern is how to add semantic information about the raw content in a document; thus, the vocabulary of a markup language is the external "marks" to be attached or embedded in a document. This concept of adding marks, or semantic instructions, to a document has been done manually in the text publishing industry for years. Figure 3.4 shows the manual markup for page layout of a school newspaper.
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