xml and oracle an overview

XML and Oracle: An Overview
Roger Schrag
Database Specialists, Inc.
www.dbspecialists.com

XML and Oracle: An Overview
•
XML Basics
•
XML’s Potential
•
Support for XML in Oracle Products

What Is XML?
•
A standard for representing structured data in
human-readable text form
•
Any type of data can be represented in XML
•
Syntax uses open and close tags similar to
HTML
•
Use tags common in your industry or make up
your own
Extensible Markup Language

XML Basics
•
XML Documents
•

Document Type Definitions
•
Document Object Model
•
Simple API for XML
•
Transformations

XML Documents
An XML document is one logical unit of data
marked up in XML, such as a purchase order or a
stock quote.
An XML datagram is a packet of data containing an
XML document that is being transported between
systems.
An XML document is said to be well formed if it
adheres to all of the syntax rules of XML.

A Sample XML Document
<?xml version="1.0"?>
<!DOCTYPE drink-recipe SYSTEM "drink-recipe.dtd">
<drink-recipe name="Fuzzy Navel">
<ingredients>
<ingredient quantity="1" unit="ounce">
Vodka </ingredient>
<ingredient quantity="1" unit="ounce">
Peach schnapps </ingredient>
<ingredient quantity="4" unit="ounce">
Orange juice </ingredient>
</ingredients>

<preparation>
<step>
Pour ingredients into a highball glass almost filled with ice.
</step>
<step>
Stir.
</step>
</preparation>
</drink-recipe>

Document Type Definition
(DTD)
•
What tags are allowed
•
What attributes are allowed within each tag
•
Which elements are required and which are
optional
•
Which tags may be nested inside of other
tags
A roadmap for how to interpret a specific
type of XML document:

A Sample DTD
<!ELEMENT drink-recipe (ingredients, preparation)>
<!ATTLIST drink-recipe name CDATA #IMPLIED>
<!ELEMENT ingredients (ingredient+)>
<!ELEMENT ingredient (#PCDATA)>

<!ATTLIST ingredient quantity CDATA #IMPLIED
unit CDATA #IMPLIED>
<!ELEMENT preparation (step+)>
<!ELEMENT step (#PCDATA)>

What Can You Do
With An XML Document?
Anything you can do with a plain text file:
•
Edit it with vi or Notepad
•
Move it between servers with FTP or HTTP
•
Store it in a VARCHAR2 or CLOB column in
your Oracle database

What Else Can You Do
With An XML Document?
•
Store it in a SYS.xmltype column in your
Oracle 9i database
•
View it with a web browser (IE 5 or Netscape 6)
•
View and edit it with JDeveloper
•
Validate it against a DTD

Document Object Model
(DOM)

•
Uses a tree structure known as a document’s infoset
•
Extract the infoset from an XML document
•
Query the infoset using a search API called XPath
•
Make changes to the infoset
•
Write the infoset back to an XML document
An API for querying and updating XML
documents
A “tree-based” API

Simple API for XML (SAX)
•
Documents are represented as a linear sequence
of parse events
•
Events occur at the start and end of elements
and text
•
Application provides custom event-handlers
•
Application code gets executed at specified
events in document
An API for scanning XML documents
An “event-based” API

XML Stylesheet Language for

Transformation (XSLT)
A process for transforming XML documents:
•
From one DTD to another
•
Between XML and other formats such as
HTML or proprietary flat file formats
An XML document using the XSLT
vocabulary defines the transformation.

XML’s Potential
Why all the excitement over XML?
•
Strict yet extensible standards
•
XML + HTTP

XML Standards
•
XML 1.0 specification defines XML and
DTD syntax
•
DOM, XPath, and XSLT are covered by a
separate specification
World Wide Web Consortium
recommendations set forth in 1998:

Standards Both
Strict and Extensible
Strict:

•
Unambiguous and unforgiving rules leave little
to the imagination
•
Vendor neutral, platform neutral, language
neutral
Extensible:
•
New industry-specific DTDs being developed
all the time
•
XSLT facilitates organizations developing
their own custom DTDs

The Synergy Between
XML and HTTP
•
HTTP is now commonplace for moving content
between systems without concern for vendor or
platform of sender or recipient.
•
Since XML documents are plain text, they can
easily be transported via HTTP.
•
While HTTP and HTML make it easy to transport
simple content, HTTP and XML together make it
easy to transport data of any structure and
complexity.

The Value of XML:

The Bottom Line
•
Vendor and platform independence in the XML
standard enables data transfer between disparate
systems.
•
DTDs and XSLT facilitate converting published data
from one format to any other.
•
XML allows you to decouple the data from the
presentation.
XML enables you to publish your complex data in the
same way that HTML enables you to publish presentation
content.

Support for XML
in Oracle Products
XML Developer Kit
–
XML Parser
–
XSLT Processor
–
XSQL Pages
–
XML SQL Utility
Oracle 9i SYS.xmltype Datatype
Oracle Text
JDeveloper
PLSXML

XML Developer Kit (XDK)
A single Oracle module that XML-enables
your Oracle database
Features based on XML standards:
–
XML parser
–
DOM and SAX support
–
XSLT processor
Oracle-specific features:
–
XSQL pages
–
XML SQL utility

XDK Availability
and Compatibility
•
Installs automatically with Oracle 9i and Oracle 8i
Release 3 (8.1.7) databases
•
Available for Oracle 8i Release 1 and 2 from the
Oracle Technology Network at technet.oracle.com
•
Not available for Oracle7 or Oracle8
Oracle’s XDK is evolving rapidly. Check OTN
periodically to see if a newer version of the XDK is
available for download.

XDK Supported Languages
Oracle’s XDK XML-enables applications
written in:
– Java – PL/SQL
– Java Beans – C and C++
Install a separate XDK for each language.

XDK Fun Facts
•
Java applications can run inside or outside
the database.
•
You must install Oracle’s JVM in the
database in order to run PL/SQL
applications that use Oracle’s XDK.
•
Some XDK features (such as SAX support
and XSQL pages) are only available in the
XDK for Java.

Features Based
on XML Standards
XML Parser, DOM, SAX, XSLT Processor
•
Multitude of Java classes.
•
PL/SQL packages such as xmlparser and
xmldom. These are really PL/SQL
wrappers encapsulating Java code.

•
Command line utilities such as oraxml and
oraxsl. These are really shell script
wrappers encapsulating Java code.

XSQL Pages (Java XDK only)
A facility for quickly publishing data in XML
•
Prepare an XML document encapsulating a SQL query using
the XSQL DTD.
•
Call a URL or enter a command at operating system prompt
to invoke the XSQL page processor.
•
Pass in criteria for the query in the URL or as command-line
arguments.
•
An XML document is created based on the query results.
•
An XSLT can be applied to the query results to transform
the output to HTML, a different DTD, or any format desired.