Re: What's a system?
This is consistent with Alfred's Essential Dictionary of Musical Notation, pg 308:Two or more staves grouped together (with a systemic barline) form a system. The first system of music is usually indented about ½ inch.
Added 2007Sep20: By implication, I take this to mean that one staff cannot be a system and should not have a systemic barline, no matter how many layers were used to produce it.