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?
Extensible Markup Language
• 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
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)
A roadmap for how to interpret a specific
type of XML document:
• 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 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)
An API for querying and updating XML
documents
•
•
•
•
•
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
A “tree-based” API
Simple API for XML (SAX)
An API for scanning XML documents
• 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 “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
World Wide Web Consortium
recommendations set forth in 1998:
• XML 1.0 specification defines XML and
DTD syntax
• DOM, XPath, and XSLT are covered by a
separate specification
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
XML enables you to publish your complex data in the
same way that HTML enables you to publish presentation
content.
• 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.
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
– Java Beans
– PL/SQL
– 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.
Components of the
XSQL Pages Framework
• Java servlet that runs under Apache (Oracle
9iAS, Oracle 9i database, or Oracle 8i Release 3
database)
• Command-line program called xsql
• XSQL page processor that gets called by either
of the above
Sample XSQL Page Output
<ROWSET>
<ROW num="1">
<ENAME>King</ENAME>
<EMPNO>7839</EMPNO>
<JOB>President</JOB>
</ROW>
<ROW num="2">
<ENAME>Blake</ENAME>
<EMPNO>7698</EMPNO>
<JOB>Manager</JOB>
</ROW>
</ROWSET>
XML SQL Utility
A facility for loading XML documents into the database and
retrieving data from the database into XML documents,
without storing the XML text in one large CLOB column
• Invoke an XSLT to transform data from any format into a
<ROWSET><ROW> style XML document.
• Convert the <ROWSET><ROW> document into a SQL
INSERT statement and load the data into a table.
• Capabilities exist for updating and deleting data as well.
• Extract data from the database into a document of any
format by reversing the process.
Oracle 9i SYS.xmltype Datatype
A new datatype that you can use on columns in tables
in an Oracle 9i database
• Oracle creates a hidden CLOB column in the table and
stores the XML document there.
• You access the XML document in ordinary SQL
statements using built-in member functions of the
SYS.xmltype datatype such as createXML, extract, or
existsNode.
• You can insert and update XML documents as a whole,
and even reference them in the WHERE clause.
• You cannot piece-wise update an XML document.
Oracle Text (interMedia)
• An Oracle facility for searching text documents stored in
CLOBs, BFILEs, or referenced by URLs.
• Adds new SQL functions CONTAINS and SCORE.
• Includes support for many document types, and linguistic
capabilities such as stemming and fuzzy matching.
• Text indexes can be created in Oracle 9i on SYS.xmltype
columns in order to index XML documents for intelligent,
XML-aware searching. New SQL functions such as
HASPATH and INPATH become available.
JDeveloper
Oracle’s interactive application development
environment
XML-aware capabilities:
• XML document editing and syntax checking
• XSLT manipulation
• XSQL page development and viewing
PLSXML
A simple PL/SQL package that returns the
result of a SQL query as an XML document
• Download PLSXML from technet.oracle.com
(search for “PLSXML”).
• A very simplistic script that demonstrates
converting table data to XML documents, but
probably has little value beyond a
demonstration.
• Oracle’s one XML offering for Oracle7 and
Oracle8 users.
Wrapping Up
• XML is a platform independent, vendor
independent method for transporting structured
data.
• XML is defined by rigid yet extensible
standards.
• Oracle has shown a huge commitment to XML
support in the Oracle 8i and Oracle 9i database.
Further Reading
• “Building Oracle XML Applications” from O’Reilly by Steve Muench
• “Oracle 9i Application Developer's Guide – XML” in the Oracle 9i
server documentation set
• http://technet.oracle.com/tech/xml (XML home page on Oracle
Technology Network)
• http://www.w3org.XML (various XML specifications including the
XML 1.0 specification)
• http://www.xml.org (Registry of XML schemas, applications, and
resources)
• http://www.xml.com (Collection of articles and information about
XML, co-founded by Tim Bray, one of the editors of the XML 1.0
standard)
• http://www.orafaq.org/faqxml.htm (XML Oracle FAQ)
Contact Information
Roger Schrag
rschrag@dbspecialists.com
http://www.dbspecialists.com
Database Specialists, Inc.
388 Market Street, Suite 400
San Francisco, CA 94111
415-344-0500