But you might want to compose various methods on the server in order to filter, just like you might want to compose various methods on the server in order to transform. Why is `collection.map(server.lookupByInternalizedId)` a special case that doesn't require `server.lookupCollectionByInternalizedId(collection)`, but `collection.filter(server.isOperationSensibleForATuesday)` is a bridge too far and for that you need `server.areOperationsSensibleForATuesday(collection)`?

I agree that, in the abstract, it's inconsistent.

But in the concrete:

* Looking up some additional data for each array element is a particularly common thing to want to do.

* We can support it nicely without having to create a library of operations baked into the protocol.

I really don't want to extend the protocol with a library of operations that you're allowed to perform. It seems like that library would just keep growing and add a lot of bloat and possibly security concerns.

(But note that apps can actually do so themselves. See: https://news.ycombinator.com/item?id=45339577 )