SAX and DOM parser

1. Seminar On:
XML & XML
Processor
Submitted By: Himanshu Soni
Branch: CS
Roll No: 1301410040
Subject: Web Technolgy
(NCS-504)
 Introduction to XML
 HTML Vs XML
 Structure of XML Document
 XML Processor
 Parser
 DOM & SAX
 References

2. Introduction to XML
What is XML ?
 XML is an acronym for “eXtensible Markup
Language”.
 XML is a markup language derived from
SGML (Standard Generalised Markup
language).
 It is used to store data in structured format.

3. HTML vs XML
HTML XML
HTML document formats and
displays web page data.
XML document carry data along
with their description.
Predefined tags (Predefined
markup language).
Not have predefined tags.You
can create and define new tags
as per your needs.(Meta
Language).
May not have closing tag. Must have closing tag.
Not Case Sensitive. Case Sensitive.
Directly Viewable in browser. Viewable if proper Stylesheet
provided.

4. HTML
Browser
StylesheetXML

5. Structure of XML Document System
 A style sheet presentation through CSS or XSL.
 A grammer structure through DTD.
 A semantics of data through XML file.
Semantics and
data,
XML file
Grammer
Structure,
DTD
Syle-sheet,
CSS or XSL

6. Structure of XML file
XML file has –
-a logical structure and
- a physical structure
Logical Structure:
It refers to different parts of
document i.e., how document is built.
Physical Structure:
It refers what document actually
contains.

7. Logical Structure
-prolog (preface or introduction to XML document)
-data instance (the real or actual data)
Prolog Data Instance
 An XMl declaration
 Processing Instruction
 A document type definition
 Comments
 White Spaces
 Element types, tags and
names
 White Spaces

8. Prolog
XML declaration
<? xml version=“1.0” encoding= “UTF-8” standalone=“no” ?>
Processing Instruction
<? xml-stylesheet type=“text/css” href=“main.css” ?>
Document Type Declaration (DTD)
<! DOCTYPE rootElement SYSTEM DTD_File_Name.dtd>
Comments
<!– Listen Here -->
White Spaces
Spaces, tabs, linebreak

9. XML Processor
 When a software program reads an XML
document and takes actions accordingly, this
is called processing the XML.
 Any program that can read and process XML
documents is known as an XML processor.
 An XML processor reads the XML file and
turns it into in-memory structures that the
rest of the program can access.

10. What is Parser?
The word parser comes from compilers. In a
compiler, a parser is the module that reads and
interprets the programming language.
Parsers are software components that decode XML
files on behalf of the application
There are two basic ways to interface a parser with
an application:
-object-based interfaces
-event-based interfaces

11. Architecture of XML Program
Divided into two parts:
• The parser deals with the XML file.
• The application consumes the content of the file through the
parser.
Here application can be very simple (such as printing information on
the screen), or quite complex (such as a browser or an editor)

12. Object-based Interface
 Using an object-based interface, the parser explicitly builds
a tree of objects that contains all the elements in the XML
document.
 Tree-based parsers deal generally small documents
Example-
<?xml version=”1.0”?>
<products>
<product>
<name>XML Editor</name>
<price>499.00</price>
</product>
<product>
<name>DTD Editor</name>
<price>199.00</price>
</product>
<products>

13. Building the tree of objects

14. Event-based Interface
 With an event-based interface, the parser does not explicitly
build a tree of objects.
 Instead, it reads the file and generates events as it finds
elements, attributes, or text in the file.
 There are events for element starts, element ends,
attributes, text content, entities, and so on.
 Event-based parsers deal generally used for large
documents
An event-based API

15. DOM
 The Document Object Model (DOM) is an
application programming interface (API) for HTML
and XML documents.
 It defines the logical structure of documents and
the way a document is accessed and manipulated
 Programmers can build documents, navigate their
structure, and add, modify, or delete elements and
content i.e.
The API allows for constructing, accessing and
manipulating the structure and content of XML
documents
 Basically, DOM is object based parser

16. DOM
DOM Parser DOM TreeXML File
A
P
I
Application

17. SAX
 SAX (Simple API for XML) is an event-
driven algorithm for parsing XML documents.
 SAX provides a mechanism for reading data from
an XML document.
 SAX parsers operate on each piece of the XML
document sequentially.
 SAX parsing is unidirectional; previously parsed
data cannot be re-read without starting the
parsing operation again

18. SAX vs DOM Parsing: Efficiency
The DOM object built by DOM parsers is usually
complicated and requires more memory storage than
the XML file itself
A lot of time is spent on construction before use
For some very large documents, this may be
impractical
SAX parsers store only local information that is
encountered during the serial traversal.
Hence, programming with SAX parsers is, in
general, more efficient but difficult to implement
sonetime.

19. References
 Benoit Marchal. XML by Example. 1 edition. QUE
(14 December 1999)
 Pankaj Sharma. Introduction to Web Technology.
S.K. Kataria & Sons
 Sumita Arora. Informatics Practices. Dhanpat Rai &
Co. (P) Ltd., Delhi 2010
 https://en.wikipedia.org/wiki/XML