Newbie: Question about XSD

Hi there,

 Please apologize if those are really simple questions. If someone
could suggest a beginer tutorial for XSD, I'd appreciate.

 I would like to convert from DICOM (a file format used in medical
fields) to XML, the goal being that I can then validate (using XSD)
this output XML. Thus I have the control over the XML layout to be
tailorded specifically for XSD validation.

A.
 In my document I have a set of entries defined by a pair of unsigned
short (unique within a document). How would one represent them in XML
?

1. Separate them:
<entry group="0010" element="0010" />
2. Group them:
<entry group-element="00100010" />
2. Group them with comma:
<entry group-element="0010,0010" />


B.
 I have to manipulate entry which value can be multiple, how would do that ?
1. As attribute:
<entry>1,2,3</entry>

2. As element:
<entry>
 <value>1</value>
 <value>2</value>
 <value>3</value>
</entry>

C.
 What if an entry contains other entry ? Should it be a different attribute ?

1.
<entry group-element="1234,5678"> <!-- special group-element value -->
 <entry group-element="0010,0010">foobar</entry>
</entry>

Or:
2.
<sequence group-element="1234,5678">
 <entry group-element="0010,0010">foobar</entry>
</sequence>


D. Is there a way to express that a particular entry (let say
0010,0010) must be present, but value is allowed to be empty.

E. Bonus question (might not be that important):
 What happen if one of the <entry> contains a jpeg file ? Is there
anything that can be done to validate it with some kind of external
codec ?

Thanks !
--
Mathieu