Globale linker
Book 1
- Chapter 1
- Chapter 2
- Chapter 3
- Chapter 4
- Chapter 5
- Chapter 6
- Chapter 7
- Chapter 8
- Chapter 9
- Chapter 10
- Chapter 11
- Chapter 12
- Chapter 13
- Chapter 14
- Chapter 15
- Chapter 16/17
- Chapter 18/19
- Chapter 20
- Chapter 21
- Chapter 22/23
Book 2
Book 2 Ch. 4 Extensibel Markup language (XML)
XML will enable users to create documents that contain more specific information about content.
XML is derived from SGML.
Markup specifically designed to affect the appearance of a document is commonly called «procedural» markup because it instructs the computer on how to render the text. Although HTML was originally created to define structure, not formatting, HTML has become somewhat procedural, with tags like <b>,<i> and <font>.
HTML was designed to display data, and to focus on how data looks.
XML was designed to describe data, and to focus on what data is. XML was developed to separate format from structure.
XML-tagged documents can be more accurately indexed by search engines.
The design goals for XML are:
- XML shall be straightforwardly usable over the Internet.
- XML shall support a wide variety of applications.
- XML shall be compatible with SGML.
- It shall be easy to write programs which process XML documents.
- The number of optional features in XML is to be kept to the absolute minimum, ideally zero.
- XML documents should be human-legible and reasonably clear.
- The XML design should be prepared quickly.
- The design of XML shall be formal and concise.
- XML documents shall be easy to create.
- Terseness in XML markup is of minimal importance.
A XML-document must be well-formed to be viewed. If it is not well-formed it will not be displayed in the browser.
Five basic rules for well-formedness:
- Tags cannot be inferred; they must be explicit. All opening tags must have corresponding end tags. All closing tags must have corresponding opening tags.
- Empty tags require a forward slash (/) character before the closing angle bracket. For example <br />
- All attribute values must be enclosed in single or double quotation marks
- Tags must nest correctly
- Tags are case sensitive and must match each other in every implementation.
A XML document can also be «valid» by following the rules set in the DTD.
A XML document must start with:
<?xml version="1.0"?>
Resources
XHTML
XHTML is the latest recommendation from W3C. XHTML combines HTML and XML to create a transition from HTML towards XML, while still providing current browsers with backward-compability.
This means that the XHTML developer who adheres to the requirements of XML well-formedness can use HTML tags and XML tags within the same document and have it be valid.
