Introduction to XML Database

1
Introduction to XML Database

• National Cheng Kung University
• Department of Electrical Engineering
• Shang-Rong Tsai

2
Outline

• Background
• XML-based databases and information system
• An XML-based Information Server

3
Background

• What is XML?
• What is a database?
• Is XML a Database?
• What is an XML Database?
• What is the goal of XML Database?
• What is the difference between RDB and XDB?
• XML in the Web

4
What is XML?

• XML stands for eXtensible Markup Language
• XML is a textual encoding system for describing
  structured documents 
• HTML documents are SGML documents which conform
  to the HTML DTDs
• DTDs (Document Type Definitions) are the syntax
  defined in SGML to describe the tag structure for
  a particular type of document.

5
What is XML? (cont.)

• XML is a subset of Standard Generalized Markup
  Language (SGML)  defined by the World Wide Web
  Consortium (Use only 10 of SGML to express 90
  power of SGML)
• HTML is for presentation only
• XML allows developers to define their own markup
  languages to express their information more
  meaningfully 
• XML lets developers describe, deliver and
  exchange structured data between applications,
  including Web servers and browsers. 

6
The features of XML

• Extensible
• Self-described
• Separate data from presentation
• Text based, platform neutral
• Unified if confirm to schema of specific domain
• Integration

7
XML Technologies

• XML/DTD
• XML Namespaces
• XSL/XSLT
• XLink/XPointer/XPath
• XML Schema
• XML data query
• XHTML

8
Definition of Database

• A database is a collection of related data
• A database represent some aspect of real world.
• A database is logically coherent collection of
  data with some inherent meaning.
• A database is designed, built, and populated with
  data for specific purpose.

9
XML and Database

• XML is basically a data format, we still need
  persistent store
• Lots of the information on the Web come from
  databases
• Data model of XML and RDBMS / OODBMS
• XML mismatches with relational databases

10
XML and Database (cont.)

• Schema mapping between XML documents and RDBMS
• data unit as XML document/element/attribute
• keys for relational tables
• data type mapping
• relationship between the stored tables

11
XML and Database (cont.)

• Query/update languages
• Indexing and search
• A new database system for XML ?
• XML-enabled database.
• native XML database (the data is actually stored
  as XML internally)

12
Is XML a Database?

• Something similar
• data storage (XML documents)
• DTD/Schema
• Query languages (XQuery, XPath, XQL, XML-QL,
  QUILT, etc.)
• Programming interface (DOM/SAX)

13
Is XML a Database? (cont.)

• Something it lacks
• transaction
• security
• indexing
• concurrent access
• query from multiple data objects
• data integrity

14
XML as platform independent data format
15
Data integration with XML
16
What is an XML Database?

• Databases that store XML documents and provide a
  view of operational data, generally either as
  indexed text or as some variant of the DOM mapped
  to an underlying data store.

17
The Goal of XML Database

• Solve the problem of mismatches between the
  XML-structure data and data model RDB products
  support
• Provide a complete solution for storing,
  accessing and manipulating XML documents
• Make the data integration and exchange easier
• Support the original goal of Web
• Human communication thru shared knowledge
• The Universe of network-accessible information

18
Difference between RDB and XDB

• Data
• Table vs. XML
• Modeling
• Logical Model
• ER vs. XML
• Physical Model
• Interface
• SQL vs. XQuery
• Application
• Transaction-based vs. Document-based

19
Storing and Retrieving XML Documents

• File System
• BLOB (Binary Large OBject)
• Native XML Databases
• Persistent DOMs (PDOMs)
• Content Management Systems
• Systems for managing fragments of human-readable
  documents and include support for editing,
  version control, and building new documents from
  existing fragments.

20
Data oriented vs. Document oriented

• Data oriented
• Documents that use XML as a data transport
• Designed for machine consumption
• Regular structure, fine-grained data, little or
  no mixed content
• Document oriented
• Designed for human consumption
• Irregular structure, larger grained data , lots
  of mixed content

21
Two typical examples of XML instances
22
Taxonomy of XML Database

• Native XML Database (NXD)
• A database fundamentally designed to store and
  manipulate XML data.
• Defines a (logical) model for an XML document and
  stores and retrieves documents according to that
  model.
• Has an XML document as its fundamental unit of
  (logical) storage, just as a relational database
  has a row in a table as its fundamental unit of
  (logical) storage.
• It is NOT required to have any particular
  underlying physical storage model.

23
Taxonomy of XML Database

• XML Enabled Database (XEDB)
• A database that has an added XML mapping layer
  provided either by the database vendor or a third
  party.

24
Applications of XML Database

• Corporate information portals
• Membership databases
• Product catalogs
• Parts databases
• Patient information tracking
• Business to business document exchange

25
Some related standard

• W3C
• XML Schema
• XPath
• XQuery
• XMLDB ORG
• XMLDB API
• XUpdate

26
XML Schema

• The purpose of a schema is to define a class of
  XML documents, and so the term "instance
  document" is often used to describe an XML
  document that conforms to a particular schema.

27
XML Schema

• XML Schema is to define and describe a class of
  XML documents by using schema constructs to
  constrain and document the meaning, usage and
  relationships of their constituent parts.
• Structure
• Data type

28
An example of XML Schema
Double Click ME!
29
XPath?

• The primary purpose of XPath is to address parts
  of an XML document.
• XPath is also designed so that it has a natural
  subset that can be used for matching.
• XPath models an XML document as a tree of nodes.
• Element nodes
• Attribute nodes
• Text nodes

30
Examples of XPath

• Collections element and .
• ./first-name
• Selecting children and descendants / and //
• author/first-name
• bookstore//title
• Collecting element children
• author/
• book//last-name
• Finding an attribute _at_
• _at_style
• price/_at_exchange

31
XQuery

• A query language that uses the structure of XML
  intelligently can express queries across all
  these kinds of data, whether physically stored in
  XML or viewed as XML via middleware.

32
An example of XQuery
List each publisher and the average price which
is greater than 100 of its books
33
XMLDB API

• XMLDB API is being developed by the XMLDB
  Initiative to facilitate the development of
  applications that function with minimal change on
  more then one XML database.
• This is roughly equivalent to the functionality
  provided by JDBC or ODBC for providing access to
  relational databases.

34
An example of XMLDB API
Double Click ME!
35
XUpdate

• XUpdate is a specification under development by
  the XMLDB Initiative to enable simpler updating
  of XML documents.
• XUpdate gives you a declarative method to insert
  nodes, remove nodes, and change nodes within an
  XML document.

36
An example of XUpdate
Double Click ME!
37
Some XML database products

• Commercial
• Tamino
• X-Hive
• Excelon
• Open Source (All Java based)
• Xindice (dbXML Core)
• eXist
• Ozone

38
Apache Xindice (dbXML Core)

• Apache Xindice is a database designed from the
  ground up to store XML data or what is more
  commonly referred to as a native XML database.
• At the present time Xindice uses XPath for its
  query language and XMLDB XUpdate for its update
  language.

39
Feature Summary

• Document Collections
• XPath Query Engine
• XML Indexing
• XMLDB XUpdate Implementation
• Java XMLDB API Implementation
• XMLObjects
• Command Line Management Tools
• CORBA Network API
• Modular Architecture

40
Collections and XML Object

• The Xindice server is designed to store
  collections of XML documents. Collections can be
  arranged in a hierarchy similar to that of a
  typical UNIX or Windows file system.
• A collection is a container for documents and
  other collections.
• XMLObjects are how dbXML provides server side
  dynamic logic. They are roughly equivalent to
  stored procedures in a traditional relational
  database.

41
An Example of Collection Path

• If you had a collection created under 'db' called
  my-collection and a collection under that called
  my-child-collection the path used when accessing
  the my-child-collection collection would be
• /db/my-collection/my-child-collection

42
Managing Documents The format of Command line
tool
Double Click ME!
43
Managing Documents Examples of Command line tool

• Adding a Document With a Given Key
• dbxml add_document -c /db/data/products -f
  fx102.xml -n fx102
• Adding a Document Without a Key
• dbxml add_document -c /db/data/products -f
  fx102.xml
• Retrieving a Document Using an ID
• dbxml retrieve_document -c /db/data/products -n
  fx102 -f result.xml
• Deleting a document using an ID
• dbxml delete_document -c /db/data/products -n
  fx102

44
Querying the Database

• Original Document
• Query
• dbxml xpath_query -c /db/data/products -q
  /product_at_product_id"120320"
• Result

lt?xml version"1.0"?gtltproduct product_id"120320"
gt ltdescriptiongtGlazed Hamlt/descriptiongtlt/produc
tgt
ltproduct product_id"120320 xmlnssrc"http//www
.dbxml.org/NodeSource"
srccol"/db/data/products" srckey"120320"gt
ltdescriptiongtGlazed Hamlt/descriptiongtlt/productgt
45
XML Object URI

• The XMLObject, associated document and method to
  execute are specified as part of the URI.
• http//localhost8080/local/test/document.xml/MyXM
  LObject/method?param1value

46
XML Object URI cont.
47
Auto Linking

• dbXML provides a facility for automating
  relational links between managed documents called
  AutoLinking.
• dbhref attribute
• Define the location of resource
• dbtype attribute
• Define the type of link replace, append, insert

48
Example of Auto Linking
49
Present Web System
50
The Original Goal of Web

• Human communication thru shared knowledge.
  Working together
• Social efficiency, understanding and scaling
• The Universe of network-accessible information

51
The problems of Current Web

• HTML is for presentation only
• Not agent and search engine friendly
• Web Automation is difficult
• Enter, search and click
• Integration is difficult
• Data format is not unified and extensible

52
The Web System in the future
53
Motivation

• There are too much useless information on
  Internet
• Solve the problems of search engine on Web
• Find out useful information for users
• Information sharing

54
XML-based Information Center
55
Four types of users
56
The Architecture of XML Storage
57
The Architecture of XML Input Tools
58
The Data Capture Template Editor
59
The Schema Editor for the DB Designer
60
The GUI for the Information Provider
61
The Input form generated by the Data Capture
Template Processor
62
Data Presentation generated by XSL and XSL
Processor
63
Epilogue

• XML make the web more automatic
• More and more Internet applications use XML
  technology
• XML can describe data in a more appropriate way
  than using Relational model
• XML plays an important role in the database area
• Information sharing using XML would be more
  efficient than HTML approach

64
Reference

• XML Database Overview
• Oasis XML and Databases, http//www.oasis-open.or
  g/cover/xmlAndDatabases.html
• XML and Database, http//www.rpbourret.com/xml/XML
  AndDatabases.htm
• Programming
• Java XML Tutorial, http//java.sun.com/xml/tutoria
  l_intro.html
• Java World, http//www.javaworld.com
• http//xml.apache.org
• http//jakarta.apache.org