The implementation of HyperRelationships needs another day of work, though the hard parts are finished now.
Time to explain the inner workings of HyperRelationships. HyperRelationships are a generalization of the binary relationships found in Neo4j. Instead of creating a relationship from a node to another node, we define a HyperRelationship as a set of Nodes each having a RelationshipRole within the HyperRelationship. For the binary case the RelationshipRoles are StartNode and EndNode. For HyperRelationships with an arity higher than 2, the Roles need to be defined for each HyperRelationshipType. A HyperRelationship is layed-out in the database as a regular relationship in the binary case. For HyperRelationship with an arity higher than 2, a Node is created subsuming the role of Relationship. >From this Node, binary relationships (regular Neo4J relationships) are created >for each Element of the relationship. The RelationshipTypes of these binary relationships are a concatenation of the name of the HyperRelationshipType used and the RelationshipRole of the attached Element. Example: Suppose we want to store the fact that Flo and Eddie give Tom, Dick and Harry a Book. This is a ternary relationship, with the following RelationshipRoles: Giver: Flo and Eddie Recipient: Tom, Dick and Harry Gift: Book The GIVE relationship is first created with a Set of Roles (Giver, Recipient and Gift). When the example relation is created the following binary relationships will be create: HyperRelationshipNode --GIVE/#/Giver--> Flo HyperRelationshipNode --GIVE/#/Giver--> Eddie HyperRelationshipNode --GIVE/#/Recipient--> Tom HyperRelationshipNode --GIVE/#/Recipient--> Dick HyperRelationshipNode --GIVE/#/Recipient--> Harry HyperRelationshipNode --GIVE/#/Gift--> Book We can now retrieve all Relationships where Flo is the Giver in a GIVE relationship, simply by concatenating GiVE and Giver into GIVE/#/Giver, and then ask all incoming Relationships with that RelationshipType. This fetches the HyperRelationship nodes and the other attached Elements of the HyperRelationship can be loaded. I added an extra interface FunctionalRelationshipRole, which restricts the number of Elements attached to a RelationshipRole within a HyperRelationship to one. The use of this amounts to something similar to having a getSingleRelationship method, which cannot throw an Exception, because multiple entries with the same RelationshipType cannot be created by design. Niels > From: [email protected] > To: [email protected] > Date: Mon, 25 Jul 2011 02:03:54 +0200 > Subject: [Neo4j] Enhanced API and HyperRelationships > > > Today I wrote a piece about the Enhanced API and about HyperRelationships, I > have been working on over the last couple of days. > > See: https://github.com/peterneubauer/graph-collections/wiki/Enhanced-API > > The API as presented in the graph-collections repo on Git is not feature > complete yet with respect to HyperRelationships. > The interfaces are there, but the implementation only works for binary > relationships at present. Need one more day for the implementation. > > I posted the Wiki page and the source code to open the discussion about these > new features. > > Niels > _______________________________________________ > Neo4j mailing list > [email protected] > https://lists.neo4j.org/mailman/listinfo/user _______________________________________________ Neo4j mailing list [email protected] https://lists.neo4j.org/mailman/listinfo/user
