Redundant artist credits

[Kaleb.G]

I would like to know the policy on redundant artist credits. For example, if an artist completely writes an album by himself, should he be credited as both composer and arranger? Also, should he be credited as performer if he plays live instruments and/or sings, lyricist if he writes the lyrics?

On a tangent, I'm wondering if there could eventually be a way to designate between "composer of new material" and "original composer of newly arranged material". I feel it would be very informative, as some artists have their work arranged for new official releases, but aren't directly involved with "composing" for it.