[elephant-devel] indexing in elephant

[Alex Mizrahi]

> 2. What we have decided is to make separate persistent class for each 
> predicate.

So, class is a predicate, right?

>3. (defpclass dependson ()
>             ((subject :accessor subject)
>             (predicate :accessor predicate)
>             (object :accessor object)))

Why do you need a predicate slot then? Predicate for dependson class is 
dependson.

> 4. How do I index a slot so that later if I have a query where I have been
provided with two slot values I should be able to get the third slot value.
For example: Force-dependson-? should return "mass" and "acceleration".

Elephant implements (on a low level) key-value pair store rather than a 
triple store.
If you want a triple store, there are basically two way to do it -- either 
use
compound keys, e.g. (subject, predicate)->object.
Or use nested key-value stores, something like
subject->(predicate->object).

Class-per-predicate essentially implements later approach with nested
key-value stores -- because each class in Elephant has its own btrees
for indices.

So, just use get-instances-by-value.  Like

(ele:get-instances-by-value 'dependson 'object value)

or

(ele:get-instances-by-value 'dependson 'subject value)

Pretty obvious, no?
Either you've got confused by your own constructs, or I've misunderstood 
something.