![Copyright © 2017, Oracle and/or its affiliates. All rights reserved. |
:Person
name = ‘John’
When does the semantic fails?
Isomorphism Cyphermorphism
4
MATCH (n:Function) -[:calls]-> (m)
WHERE n.name = ‘factorial’
RETURN m.name
:Function
name = ‘factorial’
100
:Function
name = ‘factorial_helper’
200
1 :calls
codeGraph0
:calls
m.name
‘factorial’
‘factorialHelper’
Result with isomorphism
m.name
‘factorialHelper’
Result with homomorphism
Query: which functions are
called by function ‘factorial’
:Person
name = ‘Ann’
200
100
familyTree
MATCH
(n:Person) -[:has_parent]-> () –[:has_parent]- (grandparent)
(m:Person) -[:has_parent]-> () –[:has_parent]- (grandparent)
WHERE n <> m
RETURN grandparent.name Query: “find common
grandparents”
300 400
:has_parent
:has_parent
0
:has_parent
1
2
:Person
name = ‘Klara’
:Person
name = ‘Amber’
grandparent.name
‘Amber’
Result with cyphermorphism
grandparent.name
Result with homomorphism](https://image.slidesharecdn.com/graphpatternmatchingsemantics-180115150742/85/Graph-pattern-matching-semantics-4-320.jpg)
Graph pattern matching semantics
- 1. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Graph pattern matching semantics First openCypher Implementers Meeting Oskar van Rest Oracle February 8, 2017
- 2. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Safe Harbor Statement The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle. 2
- 3. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Graph pattern matching semantics Isomorphism • Two query vertices may not map to the same data vertex – Semantic for multi-graphs is undefined Cyphermorphism • Two query edges may not map to the same data edge Homomorphism • No restriction 3 less restrictive (more powerful) easier to get started with For most queries, this works very well: users who are not aware of the semantic still get the desired result.
- 4. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | :Person name = ‘John’ When does the semantic fails? Isomorphism Cyphermorphism 4 MATCH (n:Function) -[:calls]-> (m) WHERE n.name = ‘factorial’ RETURN m.name :Function name = ‘factorial’ 100 :Function name = ‘factorial_helper’ 200 1 :calls codeGraph0 :calls m.name ‘factorial’ ‘factorialHelper’ Result with isomorphism m.name ‘factorialHelper’ Result with homomorphism Query: which functions are called by function ‘factorial’ :Person name = ‘Ann’ 200 100 familyTree MATCH (n:Person) -[:has_parent]-> () –[:has_parent]- (grandparent) (m:Person) -[:has_parent]-> () –[:has_parent]- (grandparent) WHERE n <> m RETURN grandparent.name Query: “find common grandparents” 300 400 :has_parent :has_parent 0 :has_parent 1 2 :Person name = ‘Klara’ :Person name = ‘Amber’ grandparent.name ‘Amber’ Result with cyphermorphism grandparent.name Result with homomorphism
- 5. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Pros and cons of the different semantics • They all have the same worst-case time complexity: O(nk) (n = num. data vertices, k = num. query vertices) – However, if we apply iso/cypher-morphism to recursive path queries, things blow up • Isomorphism & cyphermorphism have limitations (see previous slide) • Homomorphism may return more matches than expected and requires additional non-equality constraints • Isomorphism & cyphermorphism don’t translate as well to/from SQL 5
- 6. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Safe Harbor Statement The preceding is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle. 6