Configurable pattern matching semantics in response to #174 #175

boggle · 2017-01-25T20:17:18Z

View it here:
https://github.com/boggle/openCypher/blob/isomatch/cip/1.accepted/CIP2017-01-18-configurable-pattern-matching-semantics.adoc

…r#174

Mats-SX

I like the direction of this.

Mats-SX · 2017-01-26T14:01:02Z

cip/1.accepted/CIP2017-01-18-isomorphic-matching.adoc

+The default uniqueness mode used by `MATCH` (without a further specification of the preferred uniqueness mode) is relationship-unique matching.
+
+`MATCH ALL` does not reject any paths - not even paths containing cycles - and hence can lead to infinite result sets for the whole query.
+It is recommended that implementations generate at least a warning when static analysis is not able to proof query termination due to the chosen uniqueness mode.


proof -> prove

Mats-SX · 2017-01-26T14:01:14Z

cip/1.accepted/CIP2017-01-18-isomorphic-matching.adoc

+
+=== Proposal: Default uniqueness mode
+
+Additionally, it is proposed that a conforming implementation should provide a pre-parser option for defining a default uniqueness level for use with regular pattern matching.


I'm not convinced this kind of recommendation belongs in a CIP. Is it not well understood that an implementing system would provide ways of changing defaults?

Mats-SX · 2017-01-26T14:03:22Z

cip/1.accepted/CIP2017-01-18-isomorphic-matching.adoc

+* `closed(p)`: true if the start and the end node of `p` are the same node
+* `trail(p)`: true if `p` contains no duplicate relationships
+* `simple(p)`: true if `p` contains no duplicate relationships and either no duplicate nodes at all or the start node and the end node are the same node
+* `trek(p)`: true if `p` contains two identical consecutive relationships


What does identical mean here? Same rel-type? Same type and properties? Equal?

Mats-SX · 2017-01-26T14:04:20Z

cip/1.accepted/CIP2017-01-18-isomorphic-matching.adoc

+* `trail(p)`: true if `p` contains no duplicate relationships
+* `simple(p)`: true if `p` contains no duplicate relationships and either no duplicate nodes at all or the start node and the end node are the same node
+* `trek(p)`: true if `p` contains two identical consecutive relationships
+* `repetetive(p)`: true if `p` contains any closed subpath `q` of `size > 1` that is immediately repeated after itself in `p`


repetitive

Mats-SX · 2017-01-26T14:08:24Z

cip/1.accepted/CIP2017-01-18-isomorphic-matching.adoc

+RETURN p
+----
+
+Note that these functions naturally extend to lists.


Do you mean lists generally, or lists containing only nodes and relationships? I'm not sure I follow; what does trail(list) yielding true mean? That the list is a trail?

Mats-SX · 2017-01-26T14:11:29Z

cip/1.accepted/CIP2017-01-18-isomorphic-matching.adoc

+Changing the uniqueness mode of a sub query recursively changes the default uniqueness mode for all contained `MATCH` clauses unless it is overridden again. Examples:
+
+* `MATCH <uniqueness-modes> { MATCH ... } ...`
+* `DO <uniqueness-modes> { MATCH ... } ...`


Are MATCH and DO (this is the first time it appears on this repo I think) the two cases where you'd be able to supply these modes? What about MERGE?

Mats-SX · 2017-07-21T12:36:33Z

cip/1.accepted/CIP2017-01-18-configurable-pattern-matching-semantics.adoc

+== Motivation
+
+Currently Cypher uses pattern matching semantics that treats all patterns that occur in a `MATCH` clause as a unit (called a *uniqueness scope*) and only considers pattern instances that bind different relationships to each fixed length relationship pattern variable and to each element of a variable length relationship pattern variable.
+This has come to be called *cypermorphism* informally and is a variation of edge isomorphism.


I thought these two were synonymous; what is the variation?

'Academic' edge isomorphism only talks about a single, connected candidate walk while cyphermorphism considers all relationships bound by any pattern in the same match (even relationships bound by different, disconnected walks) for uniqueness.

Aha! Thanks for the clarification.

I don't think that this is a difference of "morphism". If one followed strict isomorphism ("path isomorphism" in Walks, Trails, Paths terms, no repeated vertices, and therefore also no repeated edges), then Cypher's current "pattern gluing" rules would apply (unless we change those rules), and we would end up evaluating matches against the compound, glued pattern, but using isomorphic semantics. Gluing may be syntactic salt, but is orthogonal to "morphism". Cyphermorphism, in my view, is no different to "Trail morphism", or "edge isomorphism".

- Add more queries - Add EBNF grammar of proposed changes

- Move definition of `disjoint()` to examples

* Now in Appendix * "bind" -> "class" (former deprecated) * Added example

romanskas · 2017-08-01T07:50:14Z

Just for the completeness: there is a fourth option (injective vertices, non-injective edges): (a)-[e1]->(b), (a)-[e2]->(b). In this case, a and b have to be distinct, but e1 and e2 can match to the same edge.

thobe · 2018-03-27T07:56:56Z

cip/1.accepted/CIP2017-01-18-configurable-pattern-matching-semantics.adoc

-                | 'DIFFERENT', ('RELATIONSHIPS' | 'EDGES'), [ VariableList ]
+PatternMorphism = 'DIFFERENT', ('NODES' | 'VERTICES')
+                | 'DIFFERENT', ('RELATIONSHIPS' | 'EDGES')
+                | 'DIFFERENT', [ VariableList ]


Optional VariableList? Is that really right?

thobe · 2018-03-27T07:59:54Z

cip/1.accepted/CIP2017-01-18-configurable-pattern-matching-semantics.adoc

-As we can see above, patterns in Cypher consist of a comma-separated list of _pattern parts_, where a pattern part is exemplified by `p = (e:Employee)-[:REPORTS_TO*1..3]->(m:Manager)`.
+PathClass = 'WALK'
+          | 'TRAIL'
+          | [ 'SIMPLE' ], 'PATH'


Does TRAIL, PATH and SIMPLE PATH really encode three different classes? If not I wonder why synonyms are allowed. (a WALK is obviously different from those three)

boggle · 2018-05-31T14:27:12Z

Note that this CIP is in a heavy state of flux in order to allow for alignment with ongoing discussions.

thobe · 2018-12-20T12:07:21Z

Aims to solve #174

felix-boeseler · 2024-03-01T20:06:10Z

Hello, are there any updates regarding this CIP? I am very interested in the proposed DIFFERENT operator functionality so I can use node isomorphism in contrast to the edge isomorphism.

Add proposal for isomorphic pattern matching in response to opencyphe…

8b6513b

…r#174

boggle added CIP language feature NOT READY FOR MERGE labels Jan 25, 2017

Mats-SX reviewed Jan 26, 2017

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Mats-SX removed the language feature label Feb 3, 2017

boggle added 2 commits July 16, 2017 15:46

Support walks, trails, paths; shortest and cheapest paths matching

ed1a824

Rework CIP

6117618

boggle changed the title ~~Add proposal for isomorphic pattern matching in response to #174~~ Configurable pattern matching semantics in response to #174 Jul 17, 2017

boggle added enhancement oCIG labels Jul 17, 2017

Simplified set of match modes and default handling

5742fdf

boggle force-pushed the isomatch branch from 804b10e to 5742fdf Compare July 19, 2017 02:08

Fix example

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Mats-SX reviewed Jul 21, 2017

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boggle and others added 12 commits July 23, 2017 15:39

Small fixups

fe68d48

Removed duplicate line

856ae1b

Restructure CIP and improve language

dd397a5

- Add more queries - Add EBNF grammar of proposed changes

Rename pattern binder to pattern variable

ce78377

Remove section on multiline patterns

cd54871

Remove section on pre-parser options

9386b70

Move functions to appendix

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- Move definition of `disjoint()` to examples

Rename Walks section to walks, trails, paths

00dc3c1

Morphism CIP: add definitions of WTP

91622f5

Structural improvements

db32e46

Tie pattern variable classes together with formal definitions

7cccfff

Tidy up referencing

8f2982d

petraselmer force-pushed the isomatch branch from 19485e6 to 8f2982d Compare July 24, 2017 15:23

boggle added 2 commits July 24, 2017 21:50

Added plural forms to grammar

254b890

Mandate correct cardinality warnings consistently

d6384c2

Reinstated pre-parser suggestions

dd74857

* Now in Appendix * "bind" -> "class" (former deprecated) * Added example

petraselmer force-pushed the isomatch branch from 73c5557 to dd74857 Compare July 25, 2017 09:32

Petra Selmer and others added 3 commits July 25, 2017 20:26

Add exemplar data graph: used for examples in CIPs

f98570c

Clarified relationship of WTP to *morphisms

fce68fa

Add expansive example using data graph

40713bb

petraselmer force-pushed the isomatch branch from 6294124 to 3895309 Compare July 26, 2017 14:07

Added a detailed example; fix-ups; language changes

50e7ac3

petraselmer force-pushed the isomatch branch from 3895309 to 50e7ac3 Compare July 26, 2017 14:08

Petra Selmer and others added 7 commits July 26, 2017 15:14

Formatted query headings so they are more readable in default GH view

5a8436d

Added TOC

08afc88

Removed Cycles and Circuits for now

efb9fee

Change to minimize breaking existing queries

1c39c76

Update examples to reflect latest changes

f8c45b4

Textual tidy-ups

c6b01b5

Updated default rules + Moved disjoint back into proposal

ac72e91

Petra Selmer and others added 5 commits January 17, 2018 16:32

Reformatted title

c139130

Updated to reflect recent discussions

8cb74ae

Merge remote-tracking branch 'me/isomatch' into isomatch

ad333a0

Fix query result blocks

3b4255f

Clarified DIFFERENT(vars) modifier

b74e09e

thobe reviewed Mar 27, 2018

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boggle closed this May 7, 2018

boggle deleted the isomatch branch May 7, 2018 11:41

boggle restored the isomatch branch May 7, 2018 11:45

petraselmer reopened this May 31, 2018

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Configurable pattern matching semantics in response to #174 #175

Configurable pattern matching semantics in response to #174 #175

boggle commented Jan 25, 2017 •

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boggle commented May 31, 2018

thobe commented Dec 20, 2018

felix-boeseler commented Mar 1, 2024


		=== Proposal: Default uniqueness mode

		Additionally, it is proposed that a conforming implementation should provide a pre-parser option for defining a default uniqueness level for use with regular pattern matching.

Configurable pattern matching semantics in response to #174 #175

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Configurable pattern matching semantics in response to #174 #175

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