Lecture Introduction to XML: Introduction to Databases and XM

7/25/2019 Lecture Introduction to XML: Introduction to Databases and XM

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Copyright IBM Corporation 2004

Course materials may not be reproduced in whole or in part without the prior written permission of IBM.

Welcome to:

3.1

Introduction to Databases and XMLIntroduction to Databases and XML


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Unit Objectives

After completing this unit, you should be able to:

List the characteristics of an XML document that help determine theright type of database

Define and describe content management databases

Compare relational database structures to XML documentstructures

List the limitations of relational data tables with structured data

Define and describe what Object-Oriented databases provide

Describe the status of XML-based queries


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Considerations

Start with what you are using the database for.

What type of application are you supporting? Is XML being used asa transport between the database and the application?

Are you using legacy data?

Are you more interested in the data or in the document structure?

Are you storing Web pages or Web pages' content?

Is your data used by other, perhaps non-XML, applications?

Are you updating the DB from XML?

Consider whether your XML document is moredata-centric or document-centric.


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Types of Databases

Relational Database (RDB) structures are not hierarchical. Muchof the world's current data exists in RDBs.

Object-Oriented Databases (OODB) are slow to catch on, but showpromise of storing XML data objects. Existing OODBs may havecomplex relationships.

Native XML database or content-management systems aredesigned specifically to store XML. Oriented towards thedocument-oriented XML systems.

Existing database systems must use some type of attachment orfilter to deal with XML data. Many RDB vendors are building thiscapability into their products.

Remember: An XML document is a hierarchical,ordered, and untyped document.



XMLApps

Connect to Database using JDBC

Retrieve an SQL result set (text string) containingthe XML document

Use the XML parser to create XML DOM from theSQL result set

Use the XSLT processor to extract the requiredelement from the XML source tree

XML editing application to update theelement contents of the result DOM

Insert updated element object into source DOMUse XSLT to write DOM to SQL

Parse XML docs with SAX

Use JDBC to update the database

record

Java Application

Databaseback end

Typical Java-basedDatabase Interchange Solution


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XML to RDB - Where Should the Data Go?

X333

XML developers

Smith

John

250243

X333

Adams

Tom432453

X333

ID last first dept-nbr ...

250243 Smith John X333 ...

432453 Adams Tom X333

...

Employee

dept-nbr department-name

X333 XML developers

Z568 Human Resources

...

Department

Key XML_DocX333

X333XMLdevelopers

Smith ...Z568 Z568 ....

XML_Table

OR



XML to RDB - And If We Have Attributes?

XML developers

SmithJohn

533-4333

[email protected]

Adams Tom

544-4444

[email protected]

ID last first dept-nbr ...

250243 Smith John X333 ...

432453 Adams Tom X333

...

Employee

dept-nbr department-name

X333 XML developers

Z568 Human Resources

...

Department

Key XML_Doc

X333

XML developers ...Z568

...

XML_Table

OR


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O O



Object-Oriented Databases

Object-Oriented Database (OODB) features:

Persistence of objects.Extend semantics of O-O programming languages.

Unification of data model and database structure.

Requires less code.

Ease of code base maintenance.

Relational Database (RDB) comparison:

Data structures must be flattened to fit joined tables.

Structures maintained in memory.

No built-in object management.

OODB real-world applications:

Risk analysis systems, telecom systems, WWW documentstructures, design and manufacturing systems, hospital patientrecord systems with complex data interrelationships.

XML N ti



XML NativeDB/Content-management Systems (1 of 2)

Can be good for document-oriented XML, much less useful fordata-oriented XML.

Good for less structured data which could result in many nullcolumns in an RDB.

Preserves physical structure of document.

No need for schema or DTD.

Limited to XML interfaces.

Do not use for data serving a variety of applications.

And provide very fast retrieval speed for entire documents.

Search for specific views of data likely to be slower then RDB.

Can only return data as XML.

XML N ti


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XML NativeDB/Content-management Systems (2 of 2)

Two main categories:Text-based storage

Store the entire document.Provide limited DB function against the document.

Provide an exact roundtrip of the document.Model-based storage

Store a DOM presentation of the XML document into an existing orcustom data store. May use an RDB underneath.

Roundtrip at the level of the underlying model (can maintain order).

Wh t b t Ch t E di ?


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What about Character Encoding?

ASC II

EBCDIC

UTF-8

Convert?

Loss of

information?

CCSID

Different languages

SBCS

DBCS

Database

Unicode


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Other Uses of XML with Databases


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Other Uses of XML with Databases

Describe databases:

TablesColumns

Foreign Keys

And so forth

Database exchange format.

Format for loading a database.

Example, different vendors

Represent result sets from database queries and updates forprograms and for humans.

Storing XML documents in databases as objects.


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Database Schemas Example


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...

... Database Schema Example

CREATE TABLE employee

(emp_nbr Char(10)

NOT NULL PRIMARY KEY,

dept_nbr Char(6),

type Varchar(40),

last Varchar(40),

first Varchar(40));

Database Create Table

Database Schemas Example

XML Query Language (XQuery) (1 of 2)


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Goals

"The goal of the XML Query WG is to produce a data model forXML documents, a set of query operators on that data model, anda query language based on these query operators."

XQuery consists of six Working Drafts:

XQuery Requirements

XQuery Use Cases

XQuery 1.0 and XPath 2.0 Data Model

XQuery 1.0 Formal SemanticsXQuery 1.0: An XML Query Language

XML Syntax for XQuery 1.0 (XQueryX)



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XQuery Goals/Usage Scenarios

Human-readable documentsData-oriented documents

Mixed model documents

Administrative data

Stream filtering

DOM queries

Native XML repositories

Catalog searchMultiple syntactic environments


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Unit Summary


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In this unit we learned:

How to compare relational database structures to XML documentstructures.

The limitations of relational data tables with structured data.

What Object-Oriented databases provide.

The status of XML-based queries.

Unit Summary

Lecture Introduction to XML: Introduction to Databases and XM

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