stac-utils / pystac

To support the implementation of radiantearth/stac-spec#1213, we need to add support for the bands attribute on assets. This attribute should be a list of band objects, and each band object should have accessors for its spec-defined attributes. These accessors should look up the attribute value in the band, then in the asset, then in the item, in a "fall-up" mechanism. This is similar to how extensions currently "fall-up" to find their values:

pystac/pystac/extensions/projection.py

Lines 345 to 346 in 1849222

    
           if asset.owner and isinstance(asset.owner, pystac.Item): 
        
               self.additional_read_properties = [asset.owner.properties]

After discussion at the STAC sprint, our initial implementation plan is:

Abstract the current behavior, implemented in extensions, to fall back to item properties if the given property isn't present on an asset or band
Create a Bands class that extends the new abstracted behavior
Add bands to Asset
Refactor all extensions to use the new abstracted behavior

This may require close coordination with any resolutions proposed to #448, e.g. #1051.

Twists

Some attributes should not "fall-up", e.g. "created" ... do we need to handle this?

	if asset.owner and isinstance(asset.owner, pystac.Item):
	self.additional_read_properties = [asset.owner.properties]

Add `Asset.bands`

Twists