[dwm] Determining client's title, class, and instance

I just started with dwm yesterday, and I'm enjoying it greatly, but have a
question concerning configuration:

Rule definition in config.def.h allows for specification of a client's
"class", "instance", and "title". I would like to be able to determine
these attributes, and have found that I can get "class" from xprop
(WM_CLASS).

Howver, xprop's output lists nothing referring to "title" or "instance". I
surmise that either "WM_NAME" or "WM_ICON_NAME" serves as "title", and have
no idea regarding "instance". I would be most appreciative if someone could
clear this up for me.

Regards and thanks,

John

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