Hello everyone,
Please see the section entitled "Host Language Embedding" here:
http://www.planettinkerpop.org/#gremlin (3 sections down)
When I was writing up this section, I noticed that most of the language drivers
that are advertised on our homepage
(http://tinkerpop.incubator.apache.org/#graph-libraries) know how to talk to
Gremlin Server via web sockets, REST, etc., but rely on the user to create a
String of their graph traversal and submit it. For instance, here is a snippet
from the Gremlin-PHP documentation:
$db = new Connection([
'host' => 'localhost',
'graph' => 'graph',
'username' => 'pomme',
'password' => 'hardToCrack'
]);
//you can set $db->timeout = 0.5; if you wish
$db->open();
$db->send('g.V(2)');
//do something with result
$db->close();
$db->send(String) is great, but it would be better if the user didn't have to
leave PHP.
Please see this ticket:
https://issues.apache.org/jira/browse/TINKERPOP-1232
I think for non-JVM languages, it would be nice if these drivers (PHP,
JavaScript, Python, etc.) didn't require the user to explicitly create
Gremlin-XXX Strings, but instead either used JINI or model-3 in the ticket
above. Lets look at model-3 as I think its the easiest and more general.
For instance, they would have a class in their native language that would
mirror the GraphTraversal API. *** I don't know any other languages well
enough, so I'm just going to do this in Groovy :), hopefully you get the
generalized point. ***
public class Test {
String s;
public Test(final String source) {
s = source;
}
public Test() {
s = "";
}
public Test V() {
s = s + ".V()";
return this;
}
public Test outE(final String label) {
s = s + ".outE(\"${label}\")";
return this;
}
public Test repeat(final Test test) {
s = s + ".repeat(${test.toString()})";
return this;
}
public String toString() {
return s;
}
}
Then, via fluency (function composition) and nesting, you could generate a
Gremlin-Groovy (or which ever ScriptEngine language) traversal String in the
backend.
gremlin> g = new Test("g");
==>g
gremlin> g.V().outE("knows")
==>g.V().outE("knows")
gremlin>
gremlin> g = new Test("g");
==>g
gremlin> g.V().repeat(new Test().outE("knows"))
==>g.V().repeat(.outE("knows"))
gremlin>
From there, that String is then submitted as you normally do with your driver.
For instance, with Gremlin-PHP, via $db->send(String).
Of course, if your driver is already on a JVM language, there is no reason to
do this (e.g. Gremlin-Scala), but if you are not on the JVM, this gives the
user host language embedding and a more natural "look and feel." Moreover, if
your language doesn't use "dot notation," you would use the natural idioms of
your language.
$g->V->outE("knows")
If anyone is interested in updating their non-JVM language driver to use this
model, I would like to write a blog post about it. Or perhaps, a tutorial for
for language designers.
Thoughts?,
Marko.
http://markorodriguez.com
