2. ObjectivesObjectives
History andMarkup languages
Comparison between XML and
HTML
XML Syntax
XML Design rationale
XML Elements and Attribute
XML DTD
XML Validation

3. HistoryHistory
SGML
HTML
XML
1985 1990
1995/98
Standardized General Markup Language
HyperText Markup Language
eXtensible Markup Language

4. Introduction of XML
 XML stands for EXTENSIBLE MARKUP
LANGUAGE.
 XML represent the text information in a
standard format .
 XML was designed to transport and store
information.
 It is used for documents containing structure
information in a reliable way.

5. What do mark up languages
do?
􀂄 Markup languages consist of a set of
markup
conventions used for encoding texts.
􀂄 A markup language specifies –
􀂄 What markup is allowed
􀂄 What markup is required
􀂄 How the mark up is distinguished from
text
􀂄 What the markup means

6. Features of XML
• XML files are text files, which can be managed
by any text editor.
• XML is very simple, because it has less than
10 syntax rules.
• XML tags are not predefined. You must define
your own tags
• XML is designed to be self-descriptive

7. ADVANTAGES OF XML
 It can represent common computer science data
structures: records, lists and trees.
 Its self-documenting format describes structure and
field names as well as specific values.
 The strict syntax and parsing requirements make the
necessary parsing algorithms extremely simple,
efficient, and consistent
 XML is heavily used as a format for document storage
and processing, both online and offline.

8. How is XML different from
HTML?
 HTML and XML have different sets of goals.
HTML was designed to display data and hence
focused on the ‘look’ of the data,
XML was designed to describe and carry data and
hence focuses on ‘what data is’.
 XML Does Not DO Anything
 HTML and XML are complementary to each
other.

9. XML Syntax Rules
 Now lets take a look at some of the
important rules of XML syntax.
 All XML Elements Must Have a Closing Tag
 XML Tags are Case Sensitive
<p>This is a
paragraph.</p>
<br />
. The tag <Letter>
is different from
the tag <letter>.

10. XML Syntax Rules
XML Elements Must be Properly Nested
XML Documents Must Have a Root Element
<b><i>This
text is bold
and
italic</i></b>
<root>
<child>
<subchild>.....</subchild>
</child>
</root>

11. XML Elements
 An Element is a technical term for a
textual unit, viewed as a structural
component.
 Different types of elements are given
different names
 The names do not express meaning and
meanings are application dependent
 XML elements are extensible

12. Authoring XML
Elements
An XML element is made up of a start tag, an end tag,
and data in between.
Example:
<director> Matthew Dunn </director>
Example of another element with the same value:
<actor> Matthew Dunn </actor>
XML tags are case-sensitive:
<CITY> <City> <city>

13. Authoring XML Attribute
(cont’d)
An attribute is a name-value pair separated by an
equal sign (=).
Example:
<City ZIP=“94608”> Emeryville </City>
Attributes are used to attach additional, secondary
information to an element.

14. XML Attributes
􀂄 XML elements can have attributes in
name/value pairs as in HTML.
􀂄 Attributes must always be in quotes.
Either single or double quotes are valid,
though double quotes are most common.
􀂄 Attributes are always contained within
the start tag of an element.

15. What is an XML DTD ?
􀂄 DTD stands for Document Type Definition.
􀂄 DTD is a formal model for defining the role
of each element
􀂄 It formally defines the relationship between
the various elements that form the documents.
􀂄 The purpose of a Document Type Definition is
to define the legal building blocks of an XML
document.

16. Document Type Definitions (DTDs 1)Document Type Definitions (DTDs 1)
XML document types can be specified using a DTD
DTD does not constrain data types
All values represented as strings in XML
DTD definition syntax
<!ELEMENT element (subelements-specification) >
<!ATTLIST element (attributes) >
… more details later
Valid XML documents refer to a DTD (or other
Schema)

17. Document Type Definitions (DTDs 2)Document Type Definitions (DTDs 2)
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE test PUBLIC "-//Webster//DTD test V1.0//EN"
<test> "test" is a document element </test>
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE test PUBLIC "-//Webster//DTD test V1.0//EN"
<test> "test" is a document element </test>
<!DOCTYPE test [
<!ELEMENT test EMPTY> ]>
<test/>
<!DOCTYPE test [
<!ELEMENT test EMPTY> ]>
<test/>
External Public DTD Declaration
Internal DTD Declaration
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE test SYSTEM "test.dtd">
<test> "test" is a document element </test>
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE test SYSTEM "test.dtd">
<test> "test" is a document element </test>
External DTD Declaration referring to a file or a URL
test =
name of
the root
element
DTD is
defined in
file test.dtd
DTD is
defined
inside XML
Application
should
know DTD

18. XML Validation
 There are two types of XML documents
 “Well formed” XML
 An XML document that conforms to the
syntax of XML is called ‘well formed’
 “Valid” XML
 An XML document that conforms to a
DTD
 Is called a ‘Valid’ DTD

19. What is a well-formed XML document ?What is a well-formed XML document ?
Well-formed documents follow basic syntax rules e.g.
there is an XML declaration in the first line
there is a single document root
all tags use proper delimiters
all elements have start and end tags
But can be minimized if empty: <br/> instead of
<br></br>
all elements are properly nested
<author> <firstname>Mark</firstname>
<lastname>Twain</lastname> </author>
appropriate use of special characters

20. XML Validator
Use our XML validator to syntax-check your XML.
XML Errors Will Stop You
Syntax-Check Your XML
Syntax-Check an XML File
Validate Your XML Against a DTD

21. Viewing XML Files
Raw XML files can be viewed in all major browsers.
Don't expect XML files to be displayed as HTML pages.
Viewing XML Files
Viewing an Invalid XML File
Look at this
XML file:
note.xml
Look at this
XML file:
note_error.xml

22. XML applications
􀂄 B2B
􀂄 EDI
􀂄 Journal publishing
􀂄 Database development

23. XML future
Given the direction in which
it is growing and the level of support that
XML has received the XML appears to
be the
future of Web publishing

24. SummarSummarYY
XML has a wide range of applications
XML is just a formalism (meta-language), unlike HTML
The W3C framework includes
General purpose (accessory, transducing, ..) languages such as XML
Schema, XSLT, XPath, XQuery, Xlink, RDF, …
Useful languages for contents (vector graphics, multimedia animation,
formulas
Other organizations
Define domain-specific vocabularies
Define alternative XML-based general purpose languages
XML is mostly used “behind the scene”, but increasingly
directly for web contents (via XSLT mostly)