How to use Pattern to restrict data

[Sean Zhang <Sean.Zhang@ins.gte.com>]

Hi,

I'm developing an XML schema and I'm using "pattern" to restrict the valid
values for certain attributes.

One specific case is the phone number, I want to exclude telephone number
starting with 800, 888, 866, etc.  How should I do this?

I was using <pattern value="[0-9]{10}"/> so that only 10 digits will be
acceptable. But I cannot find a way to exclude those numbers.  
I looked on the web and cannot find a complete reference as how to use
"pattern" and what are the possible symbols can be used in the "value"
And what does each symbol mean.  (for example, I found some schema with "?"
in value which means optional, also there are schemas specify "*", "|", etc
in value but there are no explanation as what does each mean)

Can someone point me to a good reference with full explanation?

Thanks,

Sean