Mattias Persson schrieb am 30.03.2010 um 16:06:49 (+0200):
> 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 }
> Looking at the "prune evaluator" and "return evaluator" it'd be nice
> to define them in some language, f.ex javascript, ruby or python or
> whatever. We're initially thinking of using javax.script.* stuff
> (ScriptEngine) for that, it'd probably be enough, at least to get
> things going.
XSLT, which builds on XPath, works by having the processor traverse the
tree and the user define templates featuring a match pattern. For every
node, the processor dispatches to the best matching template, from where
you can control further processing.
Now those match patterns are a subset of XPath, and rightly so: If the
user were given the full power of XPath, it would easily get horribly
expensive to determine the best matching template for a given node.
Likewise in a graph traversal, wouldn't it be reasonable to only allow
something with restricted expressive and imperative power, like the
match patterns in XSLT?
--
Michael Ludwig
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