[jira] [Created] (TINKERPOP-1277) Write a Gremlin traversal machine variant tutorial

["Marko A. Rodriguez (JIRA)" <ji...@apache.org>]

Marko A. Rodriguez created TINKERPOP-1277:
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             Summary: Write a Gremlin traversal machine variant tutorial
                 Key: TINKERPOP-1277
                 URL: https://issues.apache.org/jira/browse/TINKERPOP-1277
             Project: TinkerPop
          Issue Type: Improvement
          Components: documentation
    Affects Versions: 3.1.2-incubating, 3.2.0-incubating
            Reporter: Marko A. Rodriguez


We have discussed "Gremlin language variants" which teach people how to embed Gremlin in non-JVM languages (e.g. Python, Ruby, PHP, etc.). Developers in these non-JVM languages can then communicate with JVM-based Gremlin via GremlinServer. This all assumes that the ultimate graph system (OLTP or OLAP) is JVM-based. How about when a graph system isn't on the JVM and the graph system designers want to use Gremlin as their query language?

Like building a Gremlin language variant, building a Gremlin machine variant is not too difficult. The Gremlin traversal machine is relatively simple with only a few constructs needed -- traversals, traversers, steps, bulking. Its all pretty straightforward. 

I think it would be smart to demonstrate how to build the Gremlin machine in another language. Perhaps in a "high performance" language like C or C# or ...?. (Or perhaps just do it in like Ruby as its easy for people to build and run the code without having to do {{gcc make}}-crap) The tutorial does not need to go into all step implementations, but perhaps a few that demonstrate a filter, flatmap, map, sideEffect, branch -- as well as ones that take {{by()}}-modulators and {{TraversalParents}}. We would need to create a "TinkerGraph" in that language as well so that the implemented machine would work for it. Finally, to complete the picture, Apache TinkerPop's Gremlin-Java should be used to communicate with the non-JVM machine via a {{RemoteConnection}}! Classy.

This would complete the "Gremlin as a standard"-push. Not only can it be embedded in a host language (non JVM), but its machine can be implemented in another language as well. Thus, Gremlin is not just a JVM construct. Though Apache TinkerPop would stick to only supporting a JVM implementation of the Gremlin traversal machine.

NOTES:

* Unlike creating a Gremlin language variant, its hard to programmatically create a Gremlin machine variant. However, if the Gremlin machine variant supported {{RemoteConnection}}, then we could use Gremlin-Java's {{ProcessXXXTest}} as a way to verify that the machine variant is compliant.
* Supporting OLAP is not that difficult either. A naïve implementation of {{TraversalVertexProgram}} is only, maybe 100 lines of code. The more complicated part is the "TinkerGraphComputer"-implementation in the other language.
* The specification articulated in http://arxiv.org/abs/1508.03843 is what we should go by as its mathematically clean. We should not just try and map over the concepts 1-to-1 from Apache TinkerPop's Gremlin traversal machine.




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