[Dev] Item Collection Spec 0.2

[John Anderson]

Hi Morgen:

The plan, as I understand it (and it is in flux), is to use a new 
attribute that Andi is adding to the repository, called a set. According 
to Andi's vision, not all sets carry a cache, e.g. ref collection around 
with them, although they still look like an array from an API point of 
view. Looking up an item in these cases would involve a calcluation of 
an expression of other sets in an expression tree. So there isn't a 
bidirectional reference which would allow an item to know what sets it 
belongs in. However, it might be possible to specify that some sets have 
ref collection caches and in those cases a bidirectional reference could 
be maintained. In practice this might work for our needs, since not all 
the sets that exist map onto the user's notion of ItemCollections. I'm 
hoping sets, or a yet unnamed Item with a set attribute, eventually 
replace ItemCollections in the programmer's lexicon and the terminology 
of ItemCollections, inclusions, exclusions become more of a user 
terminology.

John

Morgen Sagen wrote:

> Ted,
>
> In the new implementation, given an item will it be easy/efficient to  
> determine all the ItemCollections that item is a member of?  Is there  
> a bi-directional reference between an ItemCollection and its member  
> items?
>
> Thanks,
> ~morgen
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