70-461 Training Kit Chapter 7, Lesson 1: XML Basics Part I

This post we summarize the XML terminologies. This is the foundation for working with XML; Next few posts we'll explore how to convert SQL table to XML format and vice versa.

A simple XML document:

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

<Customers>

    <Customer custid="1" contactname="Allen, Michael" />

    <Customer custid="2" contactname="Hassall, Mark" />

</Customers>

XML(eXtensible Markup Language) Document

Is not relational

Is Case sensitive

Is ordered (the position of elements is important)

Is well-formed when every begin tag has a matching  end tag, and if tags are nested properly such as no nested element.

Example: this is not a well formed because the elements are not nested.

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

 <Customers>

       <Customer>

           <custid>1

                                <order>2

          </custid>

     </order>    

       </Customer>

</Customers>

Has a single root node

Contain both actual data & metadata

Can contain only element, only attributes or both

Is flexible; convenient for exchange data between different systems/platforms.

XML Fragment

Doesn't have a single root node

Root Node

Encloses all other elements within a xml document.

Example:

<Root>

    <Customer custid="1" contactname="Allen, Michael" />

    <Customer custid="2" contactname="Hassall, Mark" />

</Root>

XML Tags

Begin/start tag. Example <Employees>

End tag.            Example </Employees>

XML Element

The actual tags

Example: customer is an element name.

  <Customer>

      <custid>1</custid>

      <contactname>Allen, Michael</contactname>

  </Customer>

Note white space is not allowed in an element name. example: this is invalid

<custid   >1</custid>

Tag may contain data within the tags, these are attributes

Element Data

Data between the tags

Example: 

<Customer>John Doe</Customer>

Attribute data

The data inside of a xml element tag.

     Example:

     <Customers>

         <Customer custid="1" contactname="Allen, Michael" />

         <Customer custid="2" contactname="Hassall, Mark" />

     </Customers>

Attribute data must be enclosed with single or double quotes.

Attribute names must be unique inside an element tag .

Example: this is invalid since the 2 attribute names are the same

<Customer custid1='1' custid1='2' />

Attributes within an element form a set with no order.

Always parsed as text, not XML

Example: the &lt is interpret as '&lt' not < symbol

<Customer custid="&lt 7" />

Actual Data

The data itself

Metadata

Data about the actual data. Describe the data such as properties, relationship.

Reference: Microsoft 70-461 Training Kit