The GF Eclipse Plugin

John J. Camilleri
Updated: 22 February 2013

The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. FP7-ICT-247914 (the MOLTO Project).


The aim behind developing a desktop IDE for GF is to provide more powerful tools than may be possible and/or practical in a web-based environment (the GF Web IDE). In particular, the ability to resolve identifier cross-references and browse external libraries quickly during development time is one of the primary motivations for the project.

The choice was made to develop this desktop IDE as a plugin for the Eclipse Platform as it emerged as the most popular choice among the GF developer community. Support for the platform is vast and many tools for adapting Eclipse to domain-specific languages already exist. Unlike the zero-click Web IDE approach, using the GF Eclipse plugin requires some manual installation and configuration on the development machine.


The GF Eclipse Plugin is open-source under the GNU General Public License (GPL).
The licenses that cover the rest of GF are listed here. Xtext and Eclipse are released under the Eclipse Public License (EPL).



Release history

22/02/13 : (1.5.2.x) New option for specifying include/exclude build files. Progress indicators during build.

12/06/12 : (1.5.1.x) Support for scoping when library sources not available. Performance and implementational improvements to External Library View.

19/04/12 : (1.5.0.x) Removed need for .gfexternal folder. Much improved "External Libraries" view allows you to search in current scope. Memory usage improvements in scoping implementation. Validation now occurs on file open. Re-added GF Library Path field in preferences.

04/04/12 : (1.4.3.x) Improvements to the Test Manager. Added support for arbitrary commands in launch. Made the license information clearer.

22/03/12 : (1.4.2.x) Added wizard for context-free grammars (no syntax support, though). Context-menu option for toggling the GF Nature and Builder together. Test Manager now parses languages & parameters, and includes filtering and toggling options.

14/03/12 : (1.4.1.x) GF source files can now be anywhere in project, not necessarily at top level.

06/03/12 : (1.4.0.x) Test manager view. Updated launch configurations. UI improvements, new icons. Inline contextual documentation. Correct resolution of qualified identifiers. Bug fixes and some refactoring.

07/02/12 : (1.3.0.x) Re-written underlying GF grammar.

02/02/12 : (1.2.5.x) Hugely improved scoping performance. New "Clone to new language" wizard. Improved code formatting. More efficient builder. Removed library path preference. GF runtime is now automatically found.

23/01/12 : (1.2.4.x) Logging is now done to the Eclipse Platform Log (use "Error Log" view). Tested with Eclipse 3.6.2. Bug fixes.

11/01/12 : (1.2.3.x) Updated to use Xtext 2.1.0. Links to external files now moved into new "GF Library View".

24/11/11 : (1.2.0.x) with support for "Open Declaration" (F3) function, including for external libraries.

18/11/11 : Third BETA (1.1.0.x) released, overhauled to take advantage of new compiler features. Tag-based scoping with caching for better performance. Interactive console (GF Shell) for launch configs.

11/10/11 : Second BETA (1.0.0.x) released, with improved support for qualified names, local variable bindings, selective inheritance, module outlining, and launch configurations. Also new GF Project type.

01/10/11 : Initial BETA released.

Installation & updating

System requirements

  1. Eclipse 3.6 or above.
  2. GF 3.3.3 or above. The path to GF must be set within the plugin preferences (see below).

Using the GF Resource Grammar Library requires that the RGL binaries are also installed on your system. If you are using the pre-compiled binaries but have separately downloaded the RGL sources to your system, you can optionally specify this path in the plugin preferences (see below).

Installing the plugin for the first time

Available Software Sites

In order for dependencies to be satisfied, you need to ensure that your Eclipse has the following update site URLs set:

You can set these from Preferences → Install/Update → Available Software Sites.

Eclipse preferences

How to find the Eclipse preferences window depends on your Eclipse version and/or OS, and may be either of:


  1. Inside Eclipse, go to Help → Install New Software.
  2. Add new software site using the URL:
  3. Select the GF Eclipse Plugin, and make sure the Contact all update sites during install to find required software option is checked.
  4. Click Next, accept the license agreement and install.
  5. Accept the prompt warning that the software is unsigned.
  6. Restart Eclipse when prompted.

Settings & preferences

  1. Add the GF perspective by clicking Window → Open Perspective → Other and choosing GF.
  2. Open the plugin settings by going to Preferences → Grammatical Framework (image below).
  3. The plugin will try to determine the path to your GF executable automatically, but this may need to be corrected.
    The path should include the name of the GF binary itself, e.g. /home/john/.cabal/bin/gf or C:\Users\John\GF\bin\gf.exe.
  4. The Additional path directive setting can be used if you want to avoid writing --# -path=... directives in your source files. By default it is set to .:alltenses:prelude, but can also be left blank. This is passed to GF using the --path flag.
  5. If you are using a pre-compiled version of the Resource Grammar Library (i.e. you didn't build it from source yourself) but you have the sources available on your system, then you can enter their path in the Library source path setting. This is optional and is only used for jumping to source definitions.
    You should enter an absolute system path, up to and including the src folder, e.g. /home/john/GF/lib/src/ or C:\Users\John\GF\lib\src\.
  6. You can also adjust the verbosity level of the GFEP console log in the preferences window.
Plugin preferences window

Plugin preferences window

Updating the plugin

  1. In Eclipse, go to Help → Check for updates.
  2. Any available updates will appear in the dialog. Select them and follow the usual steps.

Note: You will probably want to uncheck the Contact all update sites during install to find required software option, which is not usually needed when simply updating the plugin (it makes things go a lot slower).


Project settings

Although the plugin should take care of your project settings for you, in case anything gets messed up you can always correct them manually as follows:

Project nature

Your .project file should include the GF Project Nature as follows:



Your .project file should include the GF Builder as follows:


Specifying build files

As of GFEP ≥ 1.5.2, you are now able to explicitly a set of modules in your GF project which should be either included or excluded from the build process. In the inclusive case, this would normally contain your "top-level" modules. This can be done right-clicking on your project in the Project Explorer and choosing Properties → GF Build Settings. From here you simply tick which modules in your project the GF builder should compile:

Project-specific build settings

Project-specific build settings

When doing this, GFEP will never attempt to compile any other files in the project. Whenever you add a new top-level module or change your module hierarchy, be sure to check these build settings again.

Getting started

Some steps you can follow to get a feel of of the plugin's features.

Video tutorial

A quick run through of the major features available in the GF Eclipse Plugin.

If the video doesn't appear above, you can view it at

The Eclipse workspace and project concepts

When you run Eclipse, it asks you to create or specify a workspace on your system, which is essentially the top directory that Eclipse will "see". Any code you wish to work on inside Eclipse must reside in this workspace. A workspace contains one or more projects, which may or may not be related to each other. Generally each folder under the top-level workspace directory is considered an individual project, i.e.:


If you open an existing folder as your workspace in Eclipse, then your folders in that workspace do not automatically become Eclipse projects. To do this, you must follow the "Create new GF Project" wizard below, and give your project the exact name of the existing folder (e.g. Project1 or Project2 in the example above.)

GF Nature

The GF Nature is what makes a regular Eclipse project a GF project. If you create a new GF Project from scratch then you don't need to worry too much about them. If you already have some project set up in your Eclipse workspace, then you will need to associate the builder with your project in order for all the GF goodness to work. This will internally add the GF Builder to your project also.

As of 1.4.2, this can be done very easily by right-clicking on your project in the explorer and clicking Add/Remove GF Nature. If your project has the GF icon overlayed on it, then the GF nature and builder are correctly associated with it.

See the project settings section above if you want to mess with your .project file.

Metadata folders

GFEP will create the following metadata directories within your project:

These can be removed manually at any time, as they will always be regenerated as necessary. You will probably want to ignore these directories in your version control system.

Create a new GF Project

If you have a folder in your workspace which you want to convert into a GF Project, then you can select it from the drop-down. This folder will then appear as an Eclipse project in your workspace.

New project wizard New project wizard

New module wizard

Use the GF Module wizard from File → New → Other → GF Module:

New module wizard

New module wizard

You can find some small examples here. Download the files and manually add them to your Eclipse workspace to experiment with some of the plugin features.

Clone module wizard

If you want to clone an existing module into a new language, you can now do so via the Clone GF Module wizard. This is also available as a context menu option in the Project Explorer, via <Right click> → Grammatical Framework → Compile for new language:

Clone GF module to new language wizard

Clone GF module to new language wizard

This will create and open a new module with the relevant replacements made. Note how in this case string constants are replaced by the empty string "". This wizard currently only works on concrete and instance modules.

Newly cloned file

Newly cloned file

Workbench editor layout

Use Eclipse' own features to drag and drop your editor tabs to suit your needs.

The editor and outline view

The editor and outline view

Outline view

The Outline view in the bottom-left offers a quite overview of your module structure. Clicking any of the terms will make your cursor jump to that point in the file.

Cross-referencing errors and warnings

Notice how changing a cat definition for example will produce warnings and/or errors in other the modules.

Warnings and errors in the editor

Warnings and errors in the editor


The in-editor validation sometimes needs to be triggered/updated by a keystroke. If you can still see errors which you believe should be correct, try adding a space character to ensure the validation is re-triggered.

Sometimes you may get an entire file marked with errors, even though in fact there is only a single error which is causing the internal builder to fail. In such cases referring to the Problems view should help you locate the cause. This issue is particularly relevant when changes made to one module may induce errors in its descendants (e.g. renaming a parameter in a resource module). This behaviour will hopefully be improved in future versions.


For validation to work correctly, the project's Build Automatically option should be turned on. Each time you save a file (or some other change occurs in your project), the builder should get triggered which re-compiles any GF files which have changed. If the builder does not seem to get triggered, try to run a clean via Project → Clean...

Code formatting

Use the built-in code formatter to tidy your code automatically. Right-click in the editor and choose Format or use the keyboard shortcut Ctrl+Shift+F.

Before auto-formatting After auto-formatting

Syntax highlighting

You can change your syntax colouring styles as you wish from Preferences → Grammatical Framework → Syntax Colouring

Syntax highlighting styles

Syntax highlighting styles

Launch configurations

Set up a launch configuration from Run → Run Configurations... → Grammatical Framework. You will see the dialog below with some fields automatically filled in for you.

Launch configuration dialog

Launch configuration dialog

Run the launch config and you will see the output from the GF compiler in the console view within Eclipse.

Output from the GF compiler

Output from the GF compiler

Run As... launch shortcut

Using the Run → Run As → Compile with GF shortcut will take the current selection or active editor and do one of two things:

  1. If a launch configuration already exists which the current file in its Source filenames field, then that config will be launch directly.
  2. Otherwise, a new a launch configuration window is displayed where you will need to review and confirm the default settings before continuing.


The plugin provides its own console view named GFEP Log, which shows log messages based on the Log Level preference (Preferences → Grammatical Framework).

Additionally, every time a grammar is Run a new console is opened to display the output. This console may also serve as the interactive GF Shell, depending on the Interactive Mode checkbox in your Run Configuration.

Eclipse does not make it obvious when multiple console windows open; click on the Display Selected Console button to switch between open consoles:

Display Selected Console icon

Display Selected Console icon

If the process associated with a console window has terminated, it will be indicated in the upper-left corner as below. Such console windows can then be closed using the grey cross button:

Close terminated console icon

Close terminated console icon

The Eclipse console implementation does not support command history (up arrow) or auto-completion (tab).

External Libraries view

This view is automatically populated with a list of all the external modules referenced by the current file. Double-clicking on any item provides a quick way of opening GF files which are imported into your grammar from outside your Eclipse project, for example the GF Resource Grammar Library.

This view also provides a text box for searching within the current module's scope, as shown in the image below. Clicking the small arrow on the right-hand side of the view provides options for case sensitive and/or regular-expression based search.

External libraries view

External libraries view

Test Manager view

This feature works together with the launch configurations to make the process of running regression tests on your grammars quick and easy. As described in the GF Book (Section 10.5), the general development-test cycle (independent of GFEP) is as follows:

  1. Create a file test.trees which contains a bunch of abstract syntax trees, which you want to test
  2. Compile your grammar and linearise the trees one by one, using some command like rf -lines -tree -file=test.trees | l -table | wf -file=test.trees.out
  3. Manually correct the output in test.trees.out and save it as your gold standard file
  4. Each time you update your grammar, repeat step 2, then compare your new output against the gold standard using diff or some other comparison tool.

The Test Manager view follows this same pattern but provides a convenient graphical interface for running your test cases and also for looking at the output, just using a few clicks:

Test Manager view

Test Manager view

Note that GFEP assumes the following convention:

Extension Description
*.trees or *.sentences Test input files: trees file (for testing linearisation) and sentences file (for testing parsing)
*.trees.out or *.sentences.out Corresponding output files (generated each time a test is run)
* or * Corresponding gold standard files (manually corrected from an output file)


The GFEP writes to the Eclipse platform log. This can be accessed in two ways:

  1. By opening the Error Log view in Eclipse
  2. Accessing the file directly at <workspace>/.metadata/.log

You can set the log verbosity from Preferences → Grammatical Framework.

Common issues and fixes

No identifiers are resolved and my log contains messages saying "File does not exist."

In general, this means that something is wrong with your library path setting.

GFEP attempts to compile all of your files individually with GF, which is not the usual way in which you would compile your grammar. As a result, when looking for the RGL files, GF needs a little help via the path argument.

The normal way to do this is to specify the Library path setting from Preferences → Grammatical Framework, setting it to something like .:alltenses:prelude (this is the default setting). Note that these paths are relative to the true RGL directory, which GF should already be aware of. The value of this setting is passed to GF from GFEP using the --path flag.

The Library path setting is the same for all your GF projects. If you want finer-grain control over the path compiler option then you should use compiler pragmas in your source files, e.g.:

--# -path=.:alltenses:prelude

The advantage of this method is that the information is bound to the file, so you can freely compile your modules outside of GFEP without having to specify the path as a command line option to GF. The disadvantage is that you need to specify such a pragma in every single file (at least if you want to continue to use the GFEP).

Other strange behaviour

When things seem strange, the very first step is always to clean the project via Project → Clean.... I only support the latest version of the plugin, so make sure you are up to date too.

If problems persist, please contact me or better yet file an issue on the GitHub issue tracker (see below).

Ontology Grammar plugin

For information about the Ontology Grammar plugin developed by Ontotext AD, please refer here.

For developers

Project setup

In order to build/run the GFEP from source, you need to have the Xtext libraries available in your Eclipse workspace. You have two choices:

  1. Download the Xtext libraries from and add them to your existing Eclipse instance
  2. Download a release of Eclipse packaged together with Xtext from

In both cases make sure you get the correct version of Xtext (see below). Once you have Xtext set up, you can clone the repository locally with the following command:

git clone git://

You can then add the projects under the workspace directory to your Eclipse workspace, by using the File → Import... wizard. The individual projects are:

Namespace Description
org.grammaticalframework.eclipse.ui Covers all UI aspects of the plugin. Depends on org.grammaticalframework.eclipse (but the opposite is not true).
org.grammaticalframework.eclipse.tests Contains unit tests for the plugin. Not required for running the plugin.
org.grammaticalframework.eclipse.ontology-grammar GF Ontology Grammar Plugin for Eclipse, developed separately by Ontotext AD.
org.grammaticalframework.feature Feature project for the GF Eclipse Plugin. Exports org.grammaticalframework.eclipse and org.grammaticalframework.eclipse.ui.
org.grammaticalframework.feature.ontology-grammar Feature project for the GF Ontology Grammar Plugin. Exports org.grammaticalframework.eclipse.ontology-grammar.
org.grammaticalframework.updatesite Update site project which exports both feature projects under the same category.

Extra dependencies for unit testing project

The unit testing project (org.grammaticalframework.eclipse.tests) has an extra requirement for the library org.eclipselabs.xtext.utils.unittesting, which you will probably get complaints about when importing your projects into Eclipse. You only need to worry about this if you want to run the unit tests; otherwise you can ignore these errors. You can get more information about this library here, or just install it in Eclipse directly using the following update site URL:

Xtext version

GFEP currently uses Xtext 2.1.0.

Running from source

Once you have set up your projects (see above), you can run/debug the GFEP by following the steps here. Note that this means you will be running two instances of Eclipse simultaneously; the first debugging the second.

Building plugin package

To package the GFEP sources as .jar files and install/update the GFEP in a separate Eclipse installation, do the following:

  1. Open site.xml in the org.grammaticalframework.updatesite project with Eclipse's Site Manifest Editor (default).
  2. Synchronize the feature versions with the update site project.
  3. Click Build All and the necessary .jar files should be created/updated in the project's folder. These can then be copied, along with site.xml to any local or web directory, which becomes the "update site".

artifacts.jar and contents.jar

These are two meta-data files created by the update site project. However there are known issues with categories sporadically not working in update sites, and it seems that if you delete these 2 files then the problems are solved. More about this can be found here.

Other notes

Some have mentioned than when opening the GFEP sources, under Linux, they needed to install the following:

sudo apt-get install appmenu-gtk
sudo apt-get install gtk2-engines-pixbuf

Evaluation & feedback

Please try to use the plugin for developing your own GF projects and report any issues you come up against. Feedback (both negative and positive) on the following would be appreciated:

  1. Issues encountered with installation
  2. Incorrect support of GF syntactic constructs, module hierarchy system
  3. Performance issues (speed, resources footprint)
  4. General intuitiveness of the UI
  5. Feature wish-list
  6. Compatibilities / conflicts with other Eclipse plugins

For all bug reports and feature requests, please use the GitHub Issue Tracker.


Module types

Description of the GF module types and their icons within the GF Eclipse Plugin.

Icon Description Notes
Abstract module abstract Foods = {...}
Concrete module concrete FoodsEng of Foods = {...}
Resource module resource ResFoods = {...}
Interface interface LexFoods = {...}
Instance instance LexFoodsEng of LexFoods = {...}
Functor incomplete concrete FoodsI of Foods = {...}
Functor instantiation concrete FoodsEng of Foods = FoodsI with (...) {...}

Build command

This is the GF command run by the builder:

gf --v=0 --tags --output-dir=.gfbuild [--path=PATH] FILE