Any suggestions or tips to the questions below I have been wrestling with
would be most welcome:

I have an example XSD file I have been experimenting with.  Suppose a
user can select from 1 to 4 checkboxes on a web form:

Select your favorite sport(s):

   (checkbox) baseball
   (checkbox) football
   (checkbox) soccer
   (checkbox) golf

Futhermore, suppose a user selects all the above sports:
The xml generated from the program that reads the form variables would be:

<sport>baseball\n\football\n\soccer\n\golf</sport>

Questions:

1. what is the most effective schema statement to handle the
possiblity of the user selecting either baseball or baseball and football
or baseball, football, soccer etc..? In other words, any permutation of
checkboxes.  

I would think you would use the logical or operator (|).
I was thinking something like below, but I am getting errors such as
"Datatype error: In element 'sport': Value ........ does not match regular 
expression facet ................
   
<xsd:simpleType name="sport">
<xsd:restriction base="xsd:string">
<xsd:pattern value="baseball\\n|\\nfootball\\n|\\nsoccer\\n|golf"/>

2. Does anyone recommend any books that explain XML Schema Regular Expressions
with some good examples?  I have read Definitive XML Schema, by Walmsley.

Thanks for any tips on the above,

Fred