XML and Data Management

XML and

Data Management

• XML standards

• XML

• DTD , XML Schema

• DOM , SAX , XPath

• XSL

Overview of internet technologies for

document management and archiving

server technologies

database coupling

pure HTML

XML+XSL

Data centric XML - XML data storage

<doc>

<Auftrag>

<Kunde> Arm </Kunde>

<PC> pc400 </PC>

</Auftrag>

<Auftrag>

<Kunde> Meier </Kunde>

<PC> pc500 </PC>

</Auftrag>

<Auftrag>

<Kunde> Reich </Kunde>

<PC> pc500 </PC>

</Auftrag>

</doc>

%

Kunde

PC

auftrag(

).

).

).

auftrag(

auftrag(

Arm

pc400

Meier

pc500

Reich

pc600

doc

opening tag

closing tag

eXtended Markup Language (XML)

XML - a family of standards:

XML (eXtensible Markup Language)

data format exchangable accross different operating systems,

applications, and enterprises

often used for content

XPath

path expressions used for navigation in XML trees

used within other XML standards (e.g. XSL)

XSL (eXtensible Stylesheet Language)

used to describe layout of content / to convert data

many more standards: XQuery (

queries

) ,

Unique Standard for Content

DTD or XML Schema:

defines structure of all XML trees exchanged

=> unique data format for all participants

data formats exchangable accross company borders

New data exchange formats and languages based on XML

example:

ebXML (E-Business XML) as a basis for

OTA (Open Travel Association)

data exchange between travel agency , airline etc.

Consequence of these standards:

Separation of content and layout

content (product1.xml)

content (product2.xml)

layout (customer1.xsl)

layout ( technican2.xsl)

HTML file

Separation of content and layout (2)

Consequences:

• 1 (content) data source for different layouts

(technican, seller, customer, re-seller, ...)

• layout may change without changing content

( different logo, different seller or customer,

different employee or job, new view of data )

• reuse 1 layout for different content

( frame with company logo, ...)

• content may change without changing layout

XML on Java servers

• XML + XSL separate layout and content

• layout (.xsl file)

• content data (.xml file)

• combine them in the web server

Servlet

Browser

HTML-page

client

server

calls

generated

HTML page

input

transform

XML+XSL

Î HTML

XML

file

XSL

file

XML document as a data storage

<doc>

<Auftrag>

<Kunde> Arm </Kunde>

<PC> pc400 </PC>

</Auftrag>

<Auftrag>

<Kunde> Meier </Kunde>

<PC> pc500 </PC>

</Auftrag>

<Auftrag>

<Kunde> Reich </Kunde>

<PC> pc500 </PC>

</Auftrag>

</doc>

%

Kunde

PC

auftrag(

).

).

).

auftrag(

auftrag(

Arm

pc400

Meier

pc500

Reich

pc600

doc

opening Tag

closing Tag

XML syntax

XML - Prolog:

<?xml version="1.0" encoding="iso-8859-1" standalone="yes"?>

<?xml-stylesheet type="text/xsl" href="xmlbsp1.xsl"?>

XML - main part:

<Auftrag>

<Kunde> meier </Kunde>

<PC> pc500 </PC>

</Auftrag>

version

character set without DTD !

used stylesheet

(only inside ie5)

start tag

element

text node

/end tag

XML syntax (2)

In the XML main part:

<Angebote>

<Liefert wer=“vobis“ teil=“pc500“ >

</Liefert>

<Liefert wer=“IBM“ teil=“pc600“ / >

</Angebote>

attribute attribute value

end of tag (no text)

(arbitrarily) no text node

XML-Syntax (3)

all tags must be closed

(<tag> ... </tag> or <singleTag />)

incorrectly nested tags not allowed

( <tag1> <tag2> ... </tag1> </tag2> )

case-sensitive ( <tag> different from <Tag> )

attribute values must be quoted

( z.B. <p align="center"> )

text must be enclosed in elements

XML document as a tree

<doc>

<Kunde

name=“meier“

>

<Auftrag>

...

</Auftrag>

<Adresse>

</Adresse>

</kunde>

<Kunde>

<Auftrag/>

<Adresse/>

</Kunde>

</doc>

doc

Kunde

Kunde

Adresse

Auftrag

Auftrag

Adresse

name =

“meier“

XML node types

7 kinds of nodes:

root

- has no parent node

element

text

- leaf node (has no child node)

attribute

- leaf node (has no child node)

comment

- leaf node (has no child node)

name-space

- leaf node (has no child node)

processing-instruction

- leaf node (has no child node)

DTD and XML Schema

DTD ( the older standard ) :

+ defines the structure (nesting of tags) of the documents

<kunde>

<auftrag>

<teil> …

+ defines structural dependencies,

e.g. every auftrag contains at least one teil element

XML-Schema ( the newer standard ) additionally :

+ binds XML elements to types defined in the XML Schema

+ defines Domains

Document-Type-Definition (DTD)

<!-- DTD xmlbsp2d.dtd for example xmlbsp2d.mxl -->

<!ELEMENT Auftraege (Auftrag)* >

<!ELEMENT Auftrag ( Kunde , PC ) >

<!ELEMENT Kunde (#PCDATA) >

<!ELEMENT PC (#PCDATA) >

<?xml version="1.0" encoding="iso-8859-1" standalone="no"?>

<!DOCTYPE Auftraege SYSTEM "

xmlbsp2d.dtd

">

<?xml-stylesheet type="text/xsl" href="xmlbsp2.xsl"?>

<Auftraege>

<Auftrag>

<Kunde>Meier</Kunde>

<PC>pc500</PC>

</Auftrag>

<Auftrag> ... </Auftrag>

parsed char data

sequence

required

arbitrary many

Element declarations in DTDs

<!ELEMENT PC (#PCDATA) >

<!ELEMENT Liefert (EMPTY) >

<!ELEMENT Angebot (Liefert) >

<!ELEMENT Angebote (Liefert)* >

<!ELEMENT Auftrag (Kunde,PC) >

<!ELEMENT Zahlung (Bar|Karte) >

<!ELEMENT E ((A|B)*,C,(D)?)+ >

text (no elements)

empty

1 sub-element

? 0 or 1

* arbitrary many

+ al least 1

sub-element

sequence

choice

paranthesis

Attribute declarations in DTDs

<!-- DTD xmlbsp2d.dtd for the example xmlbsp2d.xml -->

<!ELEMENT Angebote (Liefert)* >

<!ELEMENT Liefert (EMPTY) >

<!ATTLIST Liefert wer CDATA #REQUIRED

teil CDATA #REQUIRED >

<Angebote>

<Liefert wer=“vobis“ teil=“pc500“ >

</Liefert>

<Liefert wer=“IBM“ teil=“pc600“ / >

type

(char data)

attribute

must occur

arbitrary many

root element

Axes in XML document trees

XML document

Axes:

child-axis

/child::doc/child::Kunde/child::Auftrag

/ doc / Kunde / Auftrag

attribute-axis

/child::doc/child::Kunde/

attribute::name

/ doc / Kunde

/ @ name

doc

Kunde

Kunde

Adresse

Auftrag

Auftrag

Adresse

name =

“meier“

Axes in XML document trees (2)

doc

Kunde

Adresse

Auftrag

parent

ancestor

following

following-sibling

PC

Handbuch

@nr

attribute

descendant

child

self

ancestor-or-self

descendant-or-self

Axes in XML document trees (3)

doc

Kunde

Kunde

Adresse

Auftrag

<doc>

<Kunde> … </Kunde>

<Kunde>

<name> … </name>

<Auftrag>

...

</Auftrag>

<Adresse> …

</Adresse>

</Kunde>

<Kunde> … </Kunde>

</doc>

name

Kunde

ancestor::

descendant::

following::

preceding::

self::

Axes in XML document trees (4)

Die following axes select for a given context node:

• child::

its child nodes

• descendant::

its descendants (=children and their descendants)

• parent:: the parent node (only root does not have a

parent).

• ancestor::

nodes on the path to the root (=parent and its anc's).

• following-sibling::

siblings have identical parent , following in doc order

(empty for attribute and namespace nodes).

• preceding-sibling:: inverse to

following sibling

(empty for attribute and namespace nodes).

• following::

all nodes following in doc order after context node

(excluding descendant-, attribute- & namespace-nodes).

• preceding::

all nodes preceeding in doc order before context node

(excluding ancestor-, attribute- & namespace-nodes).

• attribute:: its attributes (empty for each non-element node).

• namespace::

its namespace-nodes

Axes in XML document trees (5)

the following axes select for a given context node:

• self:: the context node itself

• descendant-or-self:: the context node and its descendants

• ancestor-or-self:: the context node and

its ancestors

When ignoring attribute nodes and namespace nodes,

the following holds for everey document node:

the axes ancestor::, descendant::, following::, preceding:: and self::

partition a document fully, i.e., the selected node sets do not overlap

but the union of all partitions contain all nodes of the document.

XML Schema example (1)

<xsd:element name="address" …>

…

<xsd:sequence>

<xsd:element name="fullname" maxOccurs="1">

…

<xsd:sequence>

<xsd:element name="firstname"/>

<xsd:element name="lastname"/>

</xsd:sequence>

…

</xsd:element>

<xsd:choice>

<xsd:element name="street"/>

<xsd:element name="POB"/>

</xsd:choice>

</xsd:sequence>

…

XML Schema example (2)

<xsd:element name="shipTo" type="CoAddress"/>

<xsd:complexType name="Address">

<xsd:complexContent>

<xsd:sequence>

<xsd:element name="fullname"/>

<xsd:element name="street"/>

</xsd:sequence>

</xsd:complexContent>

</xsd:complexType>

<xsd:complexType name="CoAddress">

<xsd:extension base="Address">

<xsd:sequence>

<xsd:element name="countrycode"/>

</xsd:sequence>

</xsd:extension>

</xsd:complexType>

</xsd:element>

XML summary

• XML :

tree structure for content

• DTD :

structure definition

• XML-Schema

additionally:

type checking and

logic consistency checking

well documented standards