Neo4J Grandchild Relationships Linked to Nodes

Question

I'm trying to model contractor relationships in Neo4J and I'm struggling with how to conceptualize subcontracts. I have nodes for Government Agencies (label: Agency) and Contractors (label:Company). Each of these have geospatial Office nodes with the HAS_OFFICE relationship. I'm thinking of creating a node that represents a Government Contract (label: Contract).

Here's what I'm struggling with: A Contract has a Government Agency (I'm thinking this is a "HAS CONTRACT" relationship) and one or more prime contractor(s) (I'm thinking this is a "PRIME" relationship). Here's where it gets complicated. Each of those primes contractors can have subcontractors under the prime contract only. Graphically, this is:

(Agency) -[HAS_CONTRACT]-> (Contract) -[PRIME]-> (Company 1) -[SUB]-> (Company 2)

The problem I'm struggling with is that the [SUB] relationship is only for certain contracts -- not all. For example:

Agency 1 -HAS-> Contract ABC -P-> Company 1 -S-> Company 2
Agency 1 -HAS-> Contract ABC -P-> Company 3 -S-> Company 4

Agency 2 -HAS-> Contract XYZ -P-> Company 1
Agency 2 -HAS-> Contract XYZ -P-> Company 4 -S-> Company 2

I want some way to search on that so I can ask cypher questions like "Find ways Agency 2 can put money on contract with Company 2." It should come back with the XYZ contract through Company 4, and NOT the XYZ contract through Company 1.

It seems like maybe storing and filtering on data within the relationship would work, but I'm struggling with how. Can I say Prima and Sub relationships have a property, "contract_id" that must match Contract['id']? If so, how?

Edit: I don't want to have to specify the contract name for the query. Based on @MarkM's reply, I'm thinking something like:

MATCH (a:Agency)-[:HAS]-(c:Contract)-[:PRIME {contract_id:c.id}]
                -(p:Company)-[:SUB {contract_id:c.id}]-(s:Company) 
RETURN s

I'd also like to be able to use things like shortestPath to find the shortest path between an agency and a contractor that follows a single contract ID.

Answer 1

I'd create the subcontractor by having two relationships, one to the contractor and one to the contract.

(:Agency)-[:ISSUES]->(con:Contract)-[:PRIMARY]->(contractor:Company)
(con:Contract)-[:SECONDARY]->(subContractor:Company)<-[:SUBCONTRACTS]-(contractor:Company)

Perhaps you can mode your use-case as a graph-gist, which is a good way of documenting and discussing modeling issues.

Answer 2

Okay take 2:

So the problem isn't captured well in the original example data — sorry for missing it. A better example is:

Agency 1 -HAS-> Contract ABC -P-> Company 1 -S-> Company 2
Agency 1 -HAS-> Contract XYZ -P-> Company 1 -S-> Company 3

Now if I ask

MATCH (a:Agency)-[:HAS_CONTRACT]-(ABC:Contract {id:ABC})-[:PRIME]
-(c:Company)-[:SUBS]-(c2) RETURN c2

I'll get both Company 2 and 3 even though only 2 is on ABC, Right?

The problem here is the data model not the query. There's no way to distinguish a company's subs because they are all connected directly to the company node. You could put a property on the sub relationship with the prime ID, but a better way that really captures the information is to add another contract node under company. Whether you label this as a different type depends on your situation.

Company1 then [:HAS] a contract which the subs are connected to. The contract can then point back to the prime contract with a relationship of something like [:PARENT] or [:PRIME] or maybe from the prime to the sub with a [:SUBCONTRACT] relationship

Now everything becomes much easier. You can find all subcontracts under a particular contract, all subcontracts a particular company [:HAS], etc. To find all subcontractors under a particular contract you could query something like this:

MATCH (contract:Contract { id:"ContractABC" })-[:PRIME]-(c:Company)
-[:HAS]->(subcontract:Contract)-[:PARENT]-(contract)
WITH c, subcontract
MATCH (subcontract)-[:SUBS]-(subcontractor:Company)
RETURN c, subcontractor

This should give you a list of all companies and their subcontractors under contract ABC. In this case Company 1, Company 2 (but not company 3).

Here's a console example: http://console.neo4j.org/?id=flhv8e I've left the original [:SUB] relationships but you might not need them.

Answer 3

This seems pretty simple; I apologize if I've misunderstood the question.

If you want subcontractors you can simply query:

MATCH (a:Agency)-[:HAS]-(:Contract)-[:PRIME]-(p:Company)-[:SUB]-(s:Company) RETURN s

This will return all companies that are subcontractors. The query matches the whole pattern. So if you want XYZ contract subcontractors you simply give it the parameter:

MATCH (a:Agency)-[:HAS]-(:Contract {contractID: XYZ})-[:PRIME]-(p:Company)-[:SUB]-(s:Company) RETURN s

You'll only get company 2.

EDIT: based on your edit:

"Find ways Agency 2 can put money on contract with Company 2"
This seems to require some domain-specific knowledge which I don't have. I assume Agency 2 can only put money on subcontractors but not primes?? I might help if you reword so we know exactly what your trying to get from the graph. From my reading it looks like you want all companies that are subcontractors under Company 2's contracts. Is that right?

If that's what you want, again you just give Neo the path:

MATCH (a:Agency: {AgencyID: 2)-[:HAS]
-(c:Contract)-[:PRIME]-(:Company)-[:SUB]-(s:Company: {companyID: 2)
RETURN c, s

This will give you a list of all contracts under XYZ for which Company 2 is a subcontractor. With the current example, it will one row: [c:Contract XYZ, s:Company 2]. If Agency 2 had more contracts under which Company 2 subcontracted, you would get more rows.

You can't do this: [:PRIME {contract_id:c.id}] [:SUB {contract_id:c.id}] because Prime and Sub relationships shouldn't have contract_id properties. They don't need them — the very fact that they are connected to a contract is enough.

One thing that might make this a little more complicated is if the subcontractors also have subcontractors, but that's not evident.