24-07-2012, 11:42 AM
eXtensible Markup Language
Markup Language.ppt (Size: 579 KB / Downloads: 26)
Introduction
XML stands for eXtensible Markup Language.
XML is the standard for structuring and exchanging data over the web
XML was designed to transport and store data, with focus on what data is, rather than how it is displayed.
XML Data Model
It is possible to characterize three main types of XML documents:
[b]Data-centric XML Documents: [/b]These documents have many small data items that follow a specific structure and hence may be extracted from a structured database.
Document-centric XML: These are documents with large amounts of text, such as news articles or books. These are few or no structured data elements in these documents.
Hybrid XML Documents: These documents may have parts that contain structured data and other parts thar are predominantly textual or unstructured.
Structure of XML data
The fundamental construct in an XML document is the element.
An element is simple a pair of matching start and end tags and all the text that appears between them.
In addition to elements, XML specifies attributes.
Attributes provide additional information about an element.
What is a schema?
- The Description of Database.
- Specified during Database Design.
- can be oriented differently: as Diagrams or Documents.
- XML follows Document oriented schema mechanism.
Using a DBMS to store the documents as text:
An object DBMS can be used to store whole XML documents as text fields within DBMS records
This approach is used if DBMS has a special module for document-processing and would also work for document-centric XML documents.
Using to store the document content as data elements:
It works for storing a collection of documents that follow a specific XML.DTD or XML schema.
Designing object database to store leaf-level data elements within XML documents.
Mapping algorithms are required to design a database schema that is compatible with the document.