grammar org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals
generate myDsl "http://www.xtext.org/example/mydsl/MyDsl"

Model:
	imports+=Import*
	greetings+=Greeting*
	refs+=GreetingRef*;

Import:
	"include" importURI=STRING;

Greeting:
	'Hello' name=ID;

GreetingRef:
	'ref' ref=[Greeting]
;

[...]
fragment = validation.ValidatorFragment auto-inject {
	composedCheck = "org.eclipse.xtext.validation.ImportUriValidator"
}
fragment = scoping.ImportURIScopingFragment auto-inject {}

//fragment = types.TypesGeneratorFragment auto-inject {}
//fragment = xbase.XbaseGeneratorFragment auto-inject {}

include "b.mydsl"
ref cGreeting //error: Couldn't resolve reference to Greeting 'cGreeting'.
ref bGreeting 

include "c.mydsl"
Hello bGreeting

Hello cGreeting

currentResource.getResourceSet().getResource(uri)