this is a very usual but quite tricky and simple ..
Using Regular Expressions
1) Select the element for which the validation is to be done.
2) Set the ‘Derived By’ property to ‘Restriction’.
3) Type the regular expression(s) in the ‘Pattern’ property.
if you want this Pattern in same schema on other elements you should do following
4) Add some text at Data_type at the Pattern element at property window. for example IEmail. This create new simple type.
5) All other elements you created, select its base data type as IEmail, instead of x:String.