Xtext: Unable to Resolve Link

I have the following Xtext grammar:

grammar dsl.miniproject.Question2.EclipsePluginLanguage with org.eclipse.xtext.common.Terminals

import "platform:/resource/Question2/model/EclipsePluginModel.ecore" 
import "http://www.eclipse.org/emf/2002/Ecore" as ecore

Plugin:
    {Plugin}
    'Plugin' Name = EntityName
    '{'             
        (documentation = Documentation)?
        (functions += Functionality)*
        manifest = Manifest
    '}'
;

Documentation:
    {Documentation}
    'description =' documentation = STRING
;

Manifest:
    {Manifest}
    'manifest'
    '{'
        (dependencies += Dependency)*
        (extensionPoints += ExtensionPoint)*    
        (extensions += Extension)*
    '}'
;

Functionality:
    {Functionality}
    'function' Name = EntityName ';'
;

Dependency:
    {Dependency}
    Name = EntityName '=>' depends = [Plugin|EntityName]
;

Extension:
    {Extension}
    Name = EntityName '->' extends = [ExtensionPoint|EntityName]
;

ExtensionPoint:
    {ExtensionPoint}
    'ExtensionPoint' Name = EntityName 
    '{'
        'ref' functions += [Functionality|EntityName] ';'       
    '}'
;

EntityName:
    ID ('.' ID)*
;

      

        
        
        
      

    

However, when writing a sample script ex:

    Plugin x{
        description = "test"

        function f;
        function f2;

        manifest{

            dep1 => x

            ExtensionPoint ep.ep1{
                ref f;
            }

            ext1 -> ep.ep1
        }    
}

      

        
        
        
      

    

I am getting the following error:

Could not find plugin link "x". Could not find a reference to functionality "f" .... etc.

This is my first attempt at xtext and I cannot figure out what I am doing wrong

Thanks in advance for your help!