XML Fundamentals

XML Fundamentals
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During 70's big companies make a lot
of integrations among them using flat
files.

The solution
How to know what is the data type?
1

The solution
Report relational data (master detail)
2

The companies had to build hugh
validators and loading process.
3

IBM invented GML (generic markup
language) and ISO adopted as SGML then
this standard was the base to define HTML
and many developers adopted it as a
exchange language.

XML stands for EXtensible Markup Language
XML is a markup language much like HTML
XML was designed to store and transport data
XML was designed to be self-descriptive
XML is a W3C Recommendation
What is XML?

It is based on tags related by nodes in a hierarchical way

XML Simplifies things
Data Sharing Data Transport Platform Changes Data Availability

XML Prolog
<?xml version="1.0" encoding="UTF-8"?>

All XML Elements must have a closing tag
<p>This is a paragraph.</p>
<br />

The tags elements are case sensitive
<table></table>
<Table></Table>

The tag elements must be properly nested
Incorrect
<b><i>This text is bold and italic</b></i>
Correct
<b><i>This text is bold and italic</i></b>

The attribute Values must be quoted
incorrect
<note date=12/11/2007>
<to>Tove</to>
<from>Jani</from>
</note>
Correct
<note date="12/11/2007">
<to>Tove</to>
<from>Jani</from>
</note>

Comments in XML

If the xml accomplish with these
rules the xml is well formed.

XML Element Text
Attributes
Other Element
Also a combination

XML Namespaces
<table>
<tr>
<td>Apples</td>
<td>Bananas</td>
</tr>
</table>
<table>
<name>African
Coffee Table</name>
<width>80</width>
<length>120</length>
</table>

Adding a prefix
<h:table>
<h:tr>
<h:td>Apples</h:td>
<h:td>Bananas</h:td>
</h:tr>
</h:table>

How to define the prefix?
<h:table
xmlns:h="http://www.w3.org/TR/html4/">
<h:tr>
<h:td>Apples</h:td>
<h:td>Bananas</h:td>
</h:tr>
</h:table>

How to constraint the data and
validate the XML Content?
Using a Xml Schema Definition File (XSD) or a Data Type
Definition file DTD
The most used is the XSD.

<?xml version="1.0" encoding="UTF-8" ?>
<xs:schema
xmlns:xs="http://www.w3.org/2001/XMLSchema">
...
</xs:schema>
We will start with the standard XML declaration followed by the xs:schema
element that defines a schema:

XSD describe the elements and attributes that an xml could
use.
It can be defined three kind of data types and with these
definitions the elements will be composed.
● Attribute
● Simple Type
● Complex Type

Attribute
<xs:attribute name="xxx" type="yyy"/>
<xs:attribute name="lang" type="xs:string" default="EN"/>
<xs:attribute name="lang" type="xs:string" use="required"/>

Simple Type
<xs:element name="idElement" type="id"/>
<xs:simpleType name="id">
<xs:restriction base="xs:integer">
<xs:minInclusive value="0"/>
<xs:maxInclusive value="100"/>
</xs:restriction>
</xs:simpleType>

Complex Type
<xs:element name="note" type="noteType"/>
<xs:complexType name="noteType" >
<xs:sequence>
<xs:element name="to" type="xs:string"/>
<xs:element name="from" type="xs:string"/>
<xs:element name="heading" type="xs:string"/>
<xs:element name="body" type="xs:string"/>
</xs:sequence>
</xs:complexType>

Commons Data types
xs:string
xs:decimal
xs:integer
xs:boolean
xs:date
xs:time

Restrictions of Values
<xs:element name="age">
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:minInclusive value="0"/>
<xs:maxInclusive value="120"/>
</xs:restriction>
</xs:simpleType>
</xs:element>

Set of Values
<xs:element name="car">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="Audi"/>
<xs:enumeration value="Golf"/>
<xs:enumeration value="BMW"/>
</xs:restriction>
</xs:simpleType>
</xs:element>

Using REGEXP
<xs:element name="letter">
<xs:simpleType>
<xs:pattern value="[a-z]"/>
</xs:restriction>
</xs:simpleType>
</xs:element>

Restriction of Length
<xs:element name="password">
<xs:simpleType>
<xs:length value="8"/>
</xs:restriction>
</xs:simpleType>
</xs:element>

DOM
Using the Document Object Model that
process the xml file as a tree structure
this method is used by HTML
The understanding and handling the xml
with this method could be easier but add
an overhead.

DOM Properties
These are some typical DOM properties:
* x.nodeName - the name of x
* x.nodeValue - the value of x
* x.parentNode - the parent node of x
* x.childNodes - the child nodes of x
* x.attributes - the attributes nodes of x

DOM Methods
● x.getElementsByTagName(name) - get all elements with a specified
tag name
● x.appendChild(node) - insert a child node to x
● x.removeChild(node) - remove a child node from x

SAXSimple API for XML is an algorithm
alternative to process a xml file sequentiality
this method could be faster but depend on
some events so could be more difficult to
manage.

Andres Felipe Rincon
PMP, TOGAF

XML Fundamentals

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