In order to work around real attributes difficulties, obscure formats, ...
Virtual attributes accessors would get/set one or multiple real attributes in a cleaner or simpler way (can accept several kind of inputs and canonicalize for exemple).
Updated by Marc Dequènes over 13 years ago
Searching vattrs is quite difficult. Even if you know which kind of objects or aspects you want, still an attribute could be real in certain objects and virtual in others, so it is impossible to guess what to find if we don't show vattrs as special attributes. The only simple way i see would be to allow post-filter of any kind of attributes, using a prefix like "filter:", which would then match real and virtual attributes without having to care of their type.