May be it could just be that the "Traversal Context" (in simple form may be just a wrapper around a HashMap) be injected into all Traversal Controls like expander etc. And this could be accessed as a method parameter or as getter() or as member variable.
On Fri, Dec 24, 2010 at 9:14 AM, Guru GV <guru...@googlemail.com> wrote: > +1, > I think a "Traversal Context" would be of great help. May be the > thoughts have to be more refined as to how the API can expose the > context in a intuitive manner. > > On Thu, Dec 23, 2010 at 9:57 PM, David Montag > <david.mon...@neotechnology.com> wrote: >> Hi, >> >> Mattias, your solution works because Amos' algo was a special case where you >> can verify the path simply by looking one step back. It's a smart solution >> to his problem! >> >> However, what about traversals where you have more complex calculations >> going on and essentially want to carry a state along with you from hop to >> hop. That state would be different for each traversal branch. Is that >> something the traversal API should support? Community, WDYT? (sorry for >> thread hijack) >> >> David >> >> On Thu, Dec 23, 2010 at 12:48 PM, Mattias Persson <matt...@neotechnology.com >>> wrote: >> >>> Hi, interesting traversal... so you're saying that paths like this could be >>> returned: >>> >>> (start)-B->()-A[P=1]->()-A[P=1]->()-B->(end) >>> >>> but not paths like this: >>> >>> (start)-A[P=1]->()-B->()-A[P=2]->(end) >>> >>> am I correct? There are common path algorithms in >>> GraphAlgoFactory< >>> http://components.neo4j.org/neo4j-graph-algo/apidocs/org/neo4j/graphalgo/GraphAlgoFactory.html >>> >but >>> they don't support an evaluator as an argument, an evaluator which >>> could >>> look like: >>> >>> { >>> public Evaluation evaluate( Path position ) >>> { >>> Relationship rel = position.lastRelationship(); >>> if ( rel == null || !rel.isType( MyRelTypes.A ) ) >>> return Evaluation.INCLUDE_AND_CONTINUE; >>> >>> Object p = rel.getProperty( "P" ); >>> Object previousP = lookBackwardsForP( position ); >>> if ( previousP != null && !p.equals( previousP ) ) >>> return Evaluation.EXCLUDE_AND_PRUNE; >>> return Evaluation.INCLUDE_AND_CONTINUE; >>> } >>> >>> private Object lookBackwardsForP( Path position ) >>> { >>> int count = 0; >>> for ( Relationship rel : position.relationships() ) >>> { >>> // Skip the first one >>> if ( count++ > 0 ) >>> { >>> if ( rel.isType( MyRelTypes.A ) ) >>> return rel.getProperty( "P" ); >>> } >>> } >>> return null; >>> } >>> } >>> >>> You could probably create a breadth first traverser with such an evaluator >>> to get your paths. I don't know about performance since each evaluation >>> needs to go back one or more steps in the path, but you could try it out. >>> >>> 2010/12/23 Amos Ben Israel <lucis.domi...@gmail.com> >>> >>> > Hello, >>> > >>> > I'm trying to find all paths between two nodes when relations can be of >>> one >>> > of two types (A or B) without repeating the same node twice - so far >>> quite >>> > simple. >>> > the complication is that relations of type A have a property P and I want >>> > only paths where P has the same value all the way (but can have two >>> > different values in two different paths). >>> > I tried to have a variable that is reset every time the traverse "starts >>> > again from the beginning" but find it difficult to know when did this >>> > happen. position.length() helps when I only have relations of type A - it >>> > does not ignore relations of type B which can be on the path. >>> > iterating over the path at each position works but seems inefficient - >>> I'd >>> > like to hear ideas for a more efficient solution. >>> > >>> > Amos. >>> > _______________________________________________ >>> > Neo4j mailing list >>> > User@lists.neo4j.org >>> > https://lists.neo4j.org/mailman/listinfo/user >>> > >>> >>> >>> >>> -- >>> Mattias Persson, [matt...@neotechnology.com] >>> Hacker, Neo Technology >>> www.neotechnology.com >>> _______________________________________________ >>> Neo4j mailing list >>> User@lists.neo4j.org >>> https://lists.neo4j.org/mailman/listinfo/user >>> >> >> >> >> -- >> David Montag >> Neo Technology, www.neotechnology.com >> Cell: 650.556.4411 >> david.mon...@neotechnology.com >> _______________________________________________ >> Neo4j mailing list >> User@lists.neo4j.org >> https://lists.neo4j.org/mailman/listinfo/user >> > _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
