Need to implement eo extension for collections

[schwehr]

https://github.com/stac-extensions/eo

Electro-Optical Extension Specification says:

• Title: Electro-Optical
• Identifier: https://stac-extensions.github.io/eo/v1.0.0/schema.json
• Field Name Prefix: eo
• Scope: Item, Collection

pystac only implements EOItemExt

[lossyrob]

I believe that's a bug in the spec. What does Collection implement? There is no mention of collections elsewhere; I think this may be a holdover from when Collections had properties that could hold common item properties, and eo information was often held there.

[schwehr]

Earth Engine currently only has stac collections and we need the band info in collections

[lossyrob]

I think what you're looking for is summaries and/or item_assets.

Summaries for the eo extension are implement on the branch here. item_assets are implemented here. This makes me think we may want to include AssetDefinitions as objects that can be wrapped in an extension so that the extension objects can be used to retrieve extension properties from asset definitions.

[lossyrob]

Based on radiantearth/stac-spec#1078 I think my understanding may be outdated (by 18 days). Asking some clarifying questions on Gitter about how collection (and now catalog) summaries are handled with stac_extensions, and how item_assets may play into this as well. If a Collection/Catalog is supposed to extend for example eo if summary information contains eo fields, then I agree we need a way to enable it on Collections/Catalogs

[lossyrob]

As described in radiantearth/stac-spec#1120, both Collection and Catalogs need implementation for most extensions as the summary information can contain extension information. This issue is resolved when extensions are implemented for each of the object types that they apply. Related to #327

[lossyrob]

Note that Catalogs are now dropping summaries (radiantearth/stac-spec#1122), so this only needs to account for Collection extensions

[duckontheweb]

@schwehr If you're game, this is something we would love to get into the 1.0 release. Any chance you'd have some availability to work on it in the next few weeks?

[schwehr]

I can try to give it a go next week. It would be nice to have.

[schwehr]

Starting to look at doing the Collection part. I'm totally not familiar with mixin stuff, but the pystac.Item Mixin seems wrong. I need to dig deeper into it to understand now ExtensionManagementMixin works

class EOExtension(
    Generic[T], PropertiesExtension, ExtensionManagementMixin[pystac.Item]
):

When the concrete classes have pystac.Item:

class ItemEOExtension(EOExtension[pystac.Item]):
class AssetEOExtension(EOExtension[pystac.Asset]):
class SummariesEOExtension(SummariesExtension):

[schwehr]

Ok... looking at datacube.py, I am starting to get it.

class EOExtension(
    Generic[T],
    PropertiesExtension,
    ExtensionManagementMixin[Union[pystac.Collection, pystac.Item]]
):

[duckontheweb]

@schwehr I'm aiming to get an RC1 release out in the next couple of days and would love to include this. Does that seem feasible?

[schwehr]

@schwehr I'm aiming to get an RC1 release out in the next couple of days and would love to include this. Does that seem feasible?

I gave it an initial look and ended up with more questions than answers. Am about to be OOO on leave for a week or two

[duckontheweb]

Okay, no worries. I'll take a crack at it and see how far I get.

[duckontheweb]

Moving this out of the RC1 release since it will represent a feature add rather than a breaking change.

[duckontheweb]

@lossyrob @schwehr I'm looking at this in more detail right now and I think I'm still confused about what exactly needs to be implemented. We have already implemented this extension for both Items and Assets, and we already have Collection-level summaries implemented. Is anything further needed?

[schwehr]

I'm confused too. I think we need someone to create a Collection example here: stac-extensions/eo#6

[duckontheweb]

I'm confident that no change is needed for this issue. My understanding is that the scope of the Electro-Optical Extension includes Collection only because extension properties can be summarized at the Collection level. We have implemented this in PySTAC, so no further changes should be necessary.