2010/4/7 Alastair James <al.ja...@gmail.com>
> >
> > > These two ways of traversing a graph complement each other, it's not
> that
> > > one is "better" than the other. Would you agree on this?
> >
>
> I think I agree. I would hope to be able to use XPath/Gremlin style
> querying
> for most things, and a more programatic system for more complex ones.
>
Something like this will come along as well rather soon (I suspect)
>
> > a JSON document describing the traverser, like:
> >
> > { "order": "depth first",
> > "uniquness": "node",
> > "return evaluator":
> > { "language": "javascript",
> > "body": "function shouldReturn( pos ) {...}" },
> > "prune evaluator":
> > { "language": "javascript",
> > "body": "function...." },
> > "relationships": [
> > { "direction": "outgoing",
> > "type": "KNOWS" },
> > { "type": "LOVES" }
> > ],
> > "max depth": 4 }
>
> Looks good for my needs. Using javascript in this form looks sensible.
>
> Any idea about the performance implications of using a javax.scripting
> language here? I guess not too severe.
>
As for javascript (Rhino engine at the moment) the code snippet will be
compiled into java code the first time and then just rerun for consecutive
calls.
>
> Is there any need for a shared context between calls to the evaluators? So
> I
> could store custom information and access it again when traversing further
> nodes. So, you could passing a 'context' object (with its initial values)
> that gets passed in as a second parameter to each evaluator function. Then
> again, this is probably bad practice....
>
We'll see what can be done about context and storing information in between
calls, there's definately a need for that.
>
> Any idea how you will handle pagination? Obviously sorting is an issue as
> you are unlikely to want the nodes in the traversal order. In my mind it
> would be nice to allow the return evaluator to return a 'sorting value'
> that
> indicates that nodes rank in the result set. E.g. sorting on a score
> attribute of the node:
>
> function shouldReturn(pos)
> {
> if (!some_condition) return false;
>
> return pos.currentNode().score;
> }
>
> But I guess this is a comment on the Neo API as a whole?
>
> Cheers
>
> Al
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--
Mattias Persson, [matt...@neotechnology.com]
Hacker, Neo Technology
www.neotechnology.com
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