Adding a Metamodel to GLSP

[glsp-bot]

Hey,

I am trying to add a custom metamodel to the glsp server. As a blueprint i am using the ecore-glsp project.

I created a metamodel for the CMMN language and added the code to existing Ecore Server, where i updated everything to use the CMMN metamodel instead of the Ecore dependencies.

Now i am having trouble generating a file header, similar to the Ecore one, which allows me to open the file and then work with the CMMN metamodel.

The header for the Ecore files looks like this:

```<?xml version='1.0' encoding='UTF-8'?>
<ecore:EPackage xmi:version='2.0' xmlns:xmi='http://www.omg.org/XMI' xmlns:ecore='http://www.eclipse.org/emf/2002/Ecore' name='testpackage' nsURI='testpackage' nsPrefix='testpackage'/>```

So to my understanding the only two parts that would point to a metamodel are ecore:EPackage and xmlns:ecore='http://www.eclipse.org/emf/2002/Ecore', however i am unsure to what i need to change them to. For the first part i choose to rename it to cmmn:MetamodelPackage with MetamodelPackage being the name of the class that does the same as the EPackage. However if i try to open the file with the following header i get the following error:

```'Class 'MetamodelPackage' is not found or is abstract. (file:/home/simon/Documents/Workspaces/EclipseSource/cmmn-editor/client/Workspace/empty.cmmn, 2, 140)'```

Which i think is strange, since EPackage is also a interface, therefore i think it cannot find the MetamodelPackage. Do i need to do a additional step in order to register the metamodel?

For reference here is my current state: https://github.com/simongraband/cmmn-editor

thanks in advance

original thread by simongraband

[tortmayr]

Hi. Looks to me like you forgot to register your metamodel on startup. This can be done by simply calling MetamodelPackage.eINSTANCE.eClass() in theCMMNServerLauncher. Similar to how it has been done for Ecore GLSP (https://github.com/eclipsesource/ecore-glsp/blob/6831c66b367732176be2f6c21b2e8fe55d629475/server/org.eclipse.emfcloud.ecore.glsp/src/main/java/org/eclipse/emfcloud/ecore/glsp/EcoreServerLauncher.java#L31)

[glsp-bot]

[simongraband]

Ah yes, i missed that, however after adding it i still get the same error.

[glsp-bot]

[simongraband]

Do you have another idea what might be wrong here?

[tortmayr]

Looks to me like your empty.cmmn file is wrong. cmmn:MetamodelPackage is not a valid element type of your metamodel. For comparison in the backup.ecore the root element is ecore:EPackage (and not ecore:EcorePackage which would be corresponding to your approach). You have to change this to the root element of the cmmn language.

[tortmayr]

In general I would recommend to also check the model resource (.ecore, .genmodel) in. Otherwise it's hard to verify if your metamodel is correct.

[glsp-bot]

[simongraband]

I pushed my model resource to https://github.com/simongraband/cmmn-editor/tree/master/server/src/main/resources.

[glsp-bot]

[simongraband]

Ok, i think i might have a wrong understanding of EPackage and EcorePackage then. I thought that EcorePackage inherits from EPackage. Therefore i thought my MetamodelPackage also inherits from EPackage (It was like this in the generated Code). And MetamodelPackage just replaces EcorePackage and EPackage stays the same.

[glsp-bot]

[simongraband]

But i need a EPackage alternative for CMMN then?

[tortmayr]

Right. You need an element that serves as root container. Maybe the Ecore Metamodel is not the best example for this. Let's have a look at the enotation.ecore:

[tortmayr]

https://spectrum.imgix.net/threads/1bb7998b-375b-4259-ac93-a261dadd6f94/a7cd55d1-2e93-42a7-8eee-961f9b7cbb33-Screenshot%2520from%25202020-06-23%252014-03-43.png?expires=1629331200000&ixlib=js-1.3.0&s=cd4c58fb4083ffd82fc215b4406d5190

[tortmayr]

The Diagram element serves as root container in this case. And the corresponding empty file would look something like this:

[tortmayr]

<enotation:Diagram xmi:version='2.0' xmlns:xmi='http://www.omg.org/XMI' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
xmlns:enotation='http://www.eclipsesource.com/glsp/ecore/notation' xsi:schemaLocation='http://www.eclipsesource.com/glsp/ecore/notation enotation.ecore'/>

[tortmayr]

I'm not familar with CMMN but you probably need something similar here. An element that maintains a set of 'CMMNElements'

[glsp-bot]

[simongraband]

I updated this and now i can load up the .cmm File with cmmn:CMMNDiagram as a root container. But now, when i add a element to the Graph it wont show up. I debugged the server and it seems like everything is working as intended.

One explanation i might have is that i need to update the enotation model to handle CMMNElements instead of EcoreElements. However i am not quite sure if this is needed at all, since CMMNElements inherit from Ecore. So do i need to update my enotation model and could this be the reason for the elements not showing up? Or could there be another reason that causes this?

[glsp-bot]

[simongraband]

(My current state is on Github)

[glsp-bot]

[simongraband]

I think i figured out why the nodes are not drawn, however i am still not sure if i need to change the enotation model.

[tortmayr]

I don't think it's necessary to change the enotation model. It's using a generic (uri-based) approach and should work for all ecore-based models. I quickly tested your current state and it looks to me like you are missing some (re)bindings in CMMNGLSPModule e.g. there is no action handler that corresponds to EcoreSaveModelActionHandler which means that the default save-handler is used. As a consequence your .ecore files will be overwritten with an (invalid) json version on save.

[glsp-bot]

[Leo Knoll]

I added a root container to my metamodel and now everything works, I was also confused by the EPackage and ECorePackage, thank you :-)