Say you have a XML like this:

:
20110506
:

Where <date> is allowed to be empty OR follow pattern ’19|20[0-9]{2}[0-1][0-9][0-3][0-9]’. How do you validate it? The solution is too simple and that is why I didn’t figure it out myself. I googled it and soon found a much smarter guy than me that said to do it like this:

:

    
                   
            <xs:pattern value="(19|20[0-9]{2}[0-1][0-9][0-3][0-9])|"/>
        
    

:

This validates YYYYMMDD type dates and also validate an empty date tag. The solution lies in the last OR operand ‘|’. You see, either the left one (the pattern) is true or the right one (which is empty). Cleaver ah? I certainly thinks soo

I have this XML snippet that I need to validate:

  Volvo

I want to validate both the attribute ‘model’ content and the element content ‘Volvo’. Here is one way of doing it (thank you Alex):

:

  <xs:complexType>
    <xs:simpleContent>
      
        <xs:attribute name="model" type="xsd:string"/>
      
    </xs:simpleContent>
  </xs:complexType>

:

The base attribute will validate the element content ‘Volvo’ and the attribute type will validate the ‘model’

Every now and then you need to validate an element or attribute agains multiple patterns.
Say an element is allowed to contain a date both in ‘YYYYnn’ format (where nn is the week number) and ‘seasonYY’ format. To solve this I use the following xsd pattern:

:
   
       
           <xs:pattern value="(19|20[0-9]{2}[0-5][0-9]) | (summer[0-9]{2}) | (winter[0-9]{2}) | (fall[0-9]{2}) | (spring[0-9]{2})"/>
       
   
:

The solution to my problem lies in the ‘|’ and parenthesis. I group the different patterns in parenthesis and separate the patterns with the OR-operator ‘|’. This way I can validate both syntaxes YYYYnn and seasonYY – only one needs to be true

There are of course other ways (shorter) to write the pattern but I choose this way because I believe it is easier to understand.