Composed UID -- beginner's question



hello,

when reading Oracle's manual for students I saw the following example on composed unique identifiers:

http://tinyurl.com/jc7ra

could anybody give me a hint what a query for extracting a row from LIST ITEM table should look like, and exemplify what its colums could be to fullfill this EM diagram? I have a problem understanding "composed UID" issue, I'd appreciate any explanation of it with some examples if posssible.

thanks,
geos
.