can pure ODD define an alternation of attribute patterns?

Hi all,

I would like to define an alternation of patterns of up to three 
attributes, where the datatype of attribute.2 and attribute.3 is uniform 
and depends on the value of attribute.1.

Something like the following (in **pseudo-markup**):

<rng:choice>
    <rng:group>  "pointer", data.pointer,                      
data.pointer </rng:group>
    <rng:group>  "character",   data.nonNegativeInteger, 
data.nonNegativeInteger </rng:group>
    <rng:group>  "byte_offset", data.nonNegativeInteger, 
data.nonNegativeInteger </rng:group>
    <rng:group>  "time_in_sec", data.integer,                    
data.integer </rng:group>
   .... etc.
</rng:choice>

I could do that in RNG, but can I do that in ODD as well?

If I understand correctly, ODD expects me to list the three attDef 
declarations in an <attList> for my new class, and to declare a new data 
type that groups the data types that I need for attribute.2 and 
attribute.3, and to make the value of attribute.1 a closed list, and 
then to slam a huuuge piece of Schematron onto this (hopefully inside 
this very class definition; I haven't checked that) that would attempt 
to rule out unwanted sequences.

Is my diagnosis correct? I probably wouldn't mind being wrong.

I also admit to having a rather hazy idea of the extent of the 
difference in "staticness" between listing potential patterns in an RNG 
schema on the one hand, and defining them in the ODD on the other. I 
mean, I am not really sure if I could <alternate> a series of 
<sequence>s containing <attDef>s. Would I end up defining a single 
attribute several times? Would/Should ODD allow me to do that?

Thanks in advance,

   Piotr