Thank you very much. I understand much better now.

I shall have a look at the specification but it is not a short document.

Thanks again.

Thanks, that does exactly what I want. It does not seems to do what w3schools says it does:

from http://www.w3schools.com/schema/schema_complex_indicators.asp

The <choice> indicator specifies...

I want to model a situation where you can have multiple children of an element, and the children can be different types and in any order. A simple example of what I mean is at [1]. I am trying to...

What are the performance implications of storing some data across 2
databases instead of duplicating this data in both databases? ie. is
example 1 significantly slower than example 2:

Example 1:...

I am a looking for recomendations for a book on database design. I have tried searching this site, and not found any good answers though I am sure this has been asked before.

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