XML DOM and SAX

2. XML: Extensible Mark-up Language T.Srinath Vidya Sagar Seema

3. XML : XML is a standard technology protocol proposed by W3C.Current version of XML is 1.0. XML stands for Extensible Mark Up Language .XML is a platform independent, language independent firewall friendly database.. The XML is text representation of data between mark ups. XML document’s extension is .xml.

4. XML document are of two types. 1.Well formed XML documents. 2.Validated XML documents.

5. 1.Well-formed XML Document: Any XML document is called a well-formed XML documents if it satisfies the following rules *It should contain only one root element. *Tag sensitive. *case sensitive.

6. 2.Validated XML Documents : If the XML documents is satisfying all the rules specified in the referred DTD , then it is called as validated XML documents.

7. DTD :(Document Type Definition) This specification is used to validate and to define the rules for the XML documents.

8. Rules of DTD : *What elements an XML document can contain. *Number of occurrences of an element. *Sequence of elements. *The attributes of an element. *Custom entities which can be used in XML document.

9. DTDs can be of 2 types : Internal DTDs-If the XML document contains the DTD inside in it, then it is called as internal DTD. External DTDs-If the XML document doesn't contains the DTD inside it but the DTD is referred from other DTD file the extension for DTD file is .dtd.

10. XML Processors or Parsers

11. What is parsing? Parsing is the process of reading an XML document and reporting its content to a client application while checking the document for well-formedness. The specific class that implements this interface varies from parser to parser.

12. Purpose of parsers : *The processor must check the basic syntax of the document for well-formedness. *the processor must replace all references to entities in an XML document by their definitions.

13. *DTDs and XML schemas can specify that certain values in an XML document during processing. *When a DTD or an XML schema is specified and the processor includes a validating parser,the structure of the XML document must be checked to ensure that its structure is legitimate.

14. *Parsers allow interpretation of XML documents. *Parsers allow processing of XML data in the XML documents. *To build XML parsers, we can use either DOM specification or SAX specification.

15. *DOM specification is given by W3C, SAX is given by SUN Micro Systems. *All the parsers that are built according to the DOM specification are called as DOM parsers, and the parsers that are built according to the SAX specification are called as SAX parsers.

16. DOM Parser (Document Object Model) : The XML DOM defines a standard way for accessing and manipulating XML document the DOM presents an XML document as a tree structure. The DOM is a W3C standard ie “World Wide Web Consortium”.

17. DOM Parser:

18. Structure of the DOM tree : *The DOM tree is composed of Node objects. *Node is an interface -some of the more important sub interfaces are Element,Attr,and Text. -An element node may have children. -Attribute and Text nodes are leaves. -Additional types are Document, comment,Entity,CDATA,Processing.

19. *The XML DOM uses an XML doc as tree structure the tree structure is called a node tree. All nodes can be accessed through the tree. The contents can be modified or deleted and new elements can be created. *The node tree shows the set of nodes and the connection between them. The tree starts at root node.

20. *The tree starts at root node and branches out to the text nodes at the lowest level of tree. In a node tree the top node is called the root -Every node except the root has exactly one parent node. -A node can have any number of children. -A leaf is node with no children. -Siblings are nodes with a same parent.

21. XML DOM:Node Tree

22. SAX parser Simple API for XML SAX :-

27. 5.Xml element end tag </first element> 6. Xml element start tag called <second element> 7.Xml text is ‘world’. 8.Xml element end tag</second element> 9.Xml element end tag </root element>

30. No structure manipulation : Because only a portion of the XML document is in memory at any one time, it is difficult to add or edit nodes using SAX. If this functionality is required, then DOM should be considered.

36. Difference between SAX and DOM SAX DOM 1.Import javax.xml.parser.*; import org.xml.sax.*; import org.xml.sax.helper.*; 1.Import javax.xml.parser.*; import org.w3c.dom.*; 2.Parses node by node. 2.Storesthe entire xml document into memory before processing. 3.Does not store the xml in memory. 3.Occupies more memory. 4.We can’t insert or delete a node. 4. 4.We can insert or delete a node. 5.Top to bottom traversing. 5.Traverse in any direction.

37. 6.SAX is an event based parser. 6.DOM is a tree model parser. 7.SAX doesn’t preserve comments. 7.DOM preserves comments. 8.SAX parser serves the client applications always only with pieces of the document. 8.DOM parser always serves the client application with the entire document.

38. SAX Parser:

39. Thank You