I’ve seen a few questions lately asking whether one can access the data/code one has in MPS from outside of MPS. The simplest way to make MPS models available to external tools is to export a root node or an entire model in XML format using NodeSerializer from the MPS-extensions project.

Here is how you can try out NodeSerializer on your model:

  1. If you are not using MPS-extensions or mbeddr platform in your project install the de.itemis.mps.utils MPS plugin.
  2. Open the MPS Console tool, import the NodeSerializer class (MPS link) by pressing Ctrl+R and searching for it in the popup.
  3. Type the following code into the console:
    new NodeSerializer(nodeRef@123456, false, "").getXMLAsString()
    
    where nodeRef@123456 is a reference to a node in your model. You write it by copying and pasting a node into the console.
  4. Execute it by pressing Ctrl+Enter (Cmd+Enter on a Mac).

You should then see the output directly in the console, it will look something like this (with extra line breaks for clarity):

<root nodeID="98682967484619562"
      conceptFQN="jetbrains.mps.baseLanguage.structure.ClassConcept"
      conceptID="f3061a53-9226-4cc5-a443-f952ceaf5816/1068390468198"
      modelID="r:5bc020f2-590a-4818-ae68-fa483b92486f"
      modelFQN="com.mbeddr.mpsutil.serializer.xml.serializer"
      isStatic="true"
      nestedName="NodeSerializer"
      shortDescription="class (c.m.m.s.xml.serializer)"
      name="NodeSerializer"
      resolveInfo="NodeSerializer"> 
  <superclass nodeID="98682967488494074"
              conceptFQN="jetbrains.mps.baseLanguage.structure.ClassifierType"
              conceptID="f3061a53-9226-4cc5-a443-f952ceaf5816/1107535904670"
              linktype="child"> 
    <classifier linktype="ref"
                targetNodeID="98682967488480204"
                targetModelID="r:5bc020f2-590a-4818-ae68-fa483b92486f"
                targetModelFQN="com.mbeddr.mpsutil.serializer.xml.serializer"
                targetConceptFQN="jetbrains.mps.baseLanguage.structure.ClassConcept"
                targetName="XMLConstants" /> 
  </superclass>
  <member nodeID="98682967484619621"
          conceptFQN="jetbrains.mps.baseLanguage.structure.PlaceholderMember"
          conceptID="f3061a53-9226-4cc5-a443-f952ceaf5816/1465982738277781862"
          linktype="child"
          shortDescription="member (c.m.m.s.xml.serializer.NodeSerializer)" />
...

(This is an excerpt from the export of the NodeSerializer class itself.)

You can also get the output as an org.jdom2.Element rather than a string, and you can customize the output via a few flags or using a SerializerProcessor implementation to alter each node after it is built by the serializer.

You may have noticed that MPS already stores its models in XML files. I don’t recommend using these files directly because the format they use is adapted to MPS' needs. It is normalized, meaning that it tries to store a given piece of information only once, and it also encodes node IDs in a particular way to save space.

When using NodeSerializer to export nodes you get a different XML structure that is not as space-efficient because it contains a lot of redundancy but this redundancy makes it much easier to process.