XML Schema testing a value and applying extra restrictions

Question

Hello all!

I have the following case: All boats have a boat type like shark , yatch and so on. I need to register which type of boat name and also how many feet the boat is, but this is where the problem arises. If the user types in a shark I need to validate that its between 15-30 feet, if he type in a yatch it needs to be between 30-60 for instance.

Any help on this?

<boat>
    <type>shark</type>
    <foot>18</foot> //validates
</boat>
<boat>
    <type>shark</type>
    <foot>14</foot> //fails
</boat>
<boat>
    <type>AnyOtherBoat</type>
    <foot>14</foot>//validates since its another type of boat than shark and yatch
</boat>

Help appriciated! Thx

Answer 1

Schematron ("a language for making assertions about patterns found in XML documents") might be able to do what you need. It allows specifying additional rules which cannot be expressed within a regular XML schema definition (XSD, RelaxNG).

Here are some articles to get you started:

1. Schematron on Wikipedia
2. Schematron: XML Structure Validation Language Using Patterns in Trees
3. Improving XML Document Validation with Schematron

Answer 2

To answer your question: No, you can't do that in XML Schema.

• Firstly, you can't use values to select which constraints to apply (but you could for elements like <shark>)
• Secondly, you can't do arithmetic tests (but you can use regex to specify the permissible strings... so you might be able to hack it.)