Lesson 8

As you learned in this module, XML promises to meet needs which HTML can never fulfill, and for which SGML may be too complex. As a metalanguage, XML is not a set of tags, but a specification for creating customized tags.
By using XML, machines will begin to understand Web pages as well as humans do. In addition, XML has uses beyond the Web that enable pervasive computing.

Now that you have completed this module, you should be able to:

1. Describe markup languages
2. Describe metalanguages
3. Describe the limitations of HTML
4. Define XML
5. List the goals of XML
6. Describe approaches to using XML

This module discusses the following terms in relation to XML:

1. DTD: The purpose of a DTD (Document Type Definition) is to define the legal building blocks of an XML document. A DTD defines the document structure with a list of legal elements and attributes.
2. Entities: In XML you can define entities to make authoring easier, or to reference the content of external documents. Entities are also useful when you create a Document Type Definition (DTD) and want to reduce its apparent complexity to keep it readable by humans.
3. Logical markup: Markup which indicates the structural meaning of a document element. Logical markup specified what the element is, not how it should look. For example, indicating that a phrase is a heading or a quotation from another source is logical markup.
4. Markup: A markup language combines text and extra information about the text. The extra information, for example about the text's structure or presentation, is expressed using markup, which is intermingled with the primary text.The best-known markup language in modern use is HTML (Hypertext Markup Language), one of the foundations of the World Wide Web.
   Historically, markup was (and is) used in the publishing industry in the communication of printed work between authors, editors, and printers.
5. Metalanguage: metalanguage is language or symbols used when language itself is being discussed or examined.
6. Parsed
7. Pervasive computing: Pervasive computing (ubicomp, or sometimes ubiqcomp) integrates computation into the environment, rather than having computers which are distinct objects. Other terms for ubiquitous computing are pervasive computing, calm technology, and things that think.
8. Procedural markup:Text with such markup is often edited with the markup visible and directly manipulated by the author. Popular procedural-markup systems include programming constructs. Therefore, macros or subroutines can be defined and invoked by name.
9. Recommendation
10. SGML: The Standard Generalized Markup Language (ISO 8879:1986 SGML) is an ISO-standard technology for defining generalized markup languages for documents.
11. Validity
12. W3C
13. Well-formedness: In XML, the phrase well-formed document is often used to describe a text that follows all the syntactic rules labelled as well-formedness rules in the XML specification: strictly speaking the phrase is tautological, since a text that does not follow these rules is not an XML document.
14. XML document instance
15. XML parser:An XML parser converts an XML document into an XML DOM object, which then can be manipulated with some other programming language such as Perl, PHP, Perl, Javascript, or Java.

Click the Quiz link below to test your understanding of the definition of XML.
XML - Quiz