Epsilon Playground¶

The Epsilon Playground is a web application for fiddling with metamodelling, modelling and automated model management using Emfatic, Flexmi and Epsilon's languages. Its back-end is implemented using Google Cloud Platform Functions and the front-end builds heavily on the Metro 4 framework. Diagrams are rendered using PlantUML and Kroki.

Emfatic Metamodels in the Playground¶

For metamodelling, the Playground uses Ecore's Emfatic textual syntax, augmented with a couple of annotations to control the graphical appearance of the metamodels.

@diagram(direction="up/down/left/right/none"): Can be attached to references (val/ref) and to attributes of enumeration type to specify the direction of the respective edge in the diagram (right by default for non-containment references, left for enumeration-typed attributes, and down for containment references). Setting the direction to none hides the edge.
@diagram(inheritance.direction="up/down/left/right/none"): Can be attached to classes to specify the direction of its inheritance edges in the diagram (up by default).
@diagram(color="<color>"): Can be attached to classes and enumerations to specify their color. Specified colors need to follow one of the PlantUML color formats.
@diagram(monochrome="true/false/<color>"): Can be attached to packages to specify that all their classes/enumerations should be displayed with the same color.

For example, the plain Emfatic metamodel below is rendered as follows:

package ptl;

class Project {
    attr String name;
    val Task[*] tasks;
    val Person[*] people;
}

abstract class Task {
    attr String name;
}

class ManualTask extends Task {
    ref Person person;
}

class AutomatedTask extends Task {

}

class Person {
    attr String name;
}

while its annotated version produces the diagram below.

package ptl;

class Project {
    attr String name;
    val Task[*] tasks;
    val Person[*] people;
}

abstract class Task {
    attr String name;
}

class ManualTask extends Task {
    @diagram(direction="up")
    ref Person person;
}

@diagram(inheritance.direction="down")
class AutomatedTask extends Task {

}

class Person {
    attr String name;
}

Changing the first line to

@diagram(monochrome="true")
package ptl;

produces the monochrome diagram below.

To share your work, click the Share button. This will create a short link that you can copy to your clipboard. Please note that the contents of the editors will be stored in the back-end of the Epsilon Playground so that they can be retrieved when you visit that link again later.

Download your work¶

To download a zipped archive of your work, click the Download button. Depending on your selection, the zipped archived will contain the model management program(s), the models and metamodels of the example, a readme.md file with instructions as well as:

Gradle/Maven: a build.gradle or pom.xml file that includes the Epsilon dependencies and the ANT tasks you need to run the example from the command line
Ant (Eclipse): a build.xml file that in includes the ANT tasks you need to run the example from within Eclipse
Java (Gradle)/Java (Maven): a Java class that runs the model management program using Epsilon's API, and a build.gradle or pom.xml file that includes the Epsilon dependencies

Custom examples¶

You can launch the Playground with a custom set of examples by appending an examples parameter to the URL, which points to a JSON file that contains your own examples. For instance, this link below launches the Playground with its default set of examples.

https://eclipse.org/epsilon/playground/?examples=https://raw.githubusercontent.com/eclipse/epsilon-website/master/mkdocs/docs/playground/examples/examples.json

The structure of examples.json should be self-explanatory but if you have any questions, please let us know.

Settings¶

Through the Settings dialog, you can show/hide the different panels of the playground as well as line numbers in editors. You can also hide a panel by middle-clicking and maximise/restore it by double-clicking on its title.

If you hide the program panel, you can still run the program it contains using the Ctrl+S or Cmd+S keyboard shortcut.

Docker container¶

If the Playground is a critical dependency for you (e.g. to support a training course), you may want to run your own instance through a Docker container. Despite using automated testing with Cypress, as we are evolving the Playground, we may indadvertedly introduce regressions that break the Playground and make (parts of it) unusable for a period of time.

Fair usage policy¶

The cost of running Epsilon Playground is proportional to the number of requests made to its Google Cloud Platform back-end (i.e. execution of programs and rendering of diagrams). With fair usage we can comfortably afford this cost and keep the Playground operational, but in case of excessive use we may have to take it down with no notice. To keep costs down, server-side operations that take more than 60 seconds to complete are automatically terminated. For extensive use, large models, or complex programs, please use the development tools / Java libraries provided on the Epsilon website instead, or run your own instance of the Epsilon Playground in a Docker container.

Reporting bugs and requesting help¶

Please submit bug reports using GitHub Issues and ask for help in Epsilon's forum. You can submit feature requests too but please keep in mind that the Playground is not a replacement for Epsilon's Eclipse-based development tools. The Playground has been tested on recent versions of Firefox and Chrome. It's unlikely that we'll be able to invest too much effort in making it compatible with older/other browsers but any pull requests you may be able to contribute are always welcome.