Flowchart to HTML

Problem Description

In this example, we will look at converting flowchart elements into HTML elements. The problem is open-ended, meaning, there is no one solution but rather the project will contain many small examples that showcase a multitude of operations for each documented MTL. The flowchart which should be used as the source model of the project is depicted in the diagram below:

graph LR
  A[Begin] -->|Start| B[Wake up];
  B --> C{Is it really too early?};
  C --> |Yes| D[Sleep];
  C --> |No| E[Get up]
  D --> |Some Time Passes| B;

Wakeup Flowchart

Here is how the different models in this project depend on each other:

graph BT
    B[Source Model] -->|conforms to| A[Flowchart Metamodel];
    C[MT Execution Engine] -->|reads| B;
    C -->|executes| D[MT Definition];
    C -->|writes| E[Target Model];
    D -->|uses| A;
    E -->|conforms to| F[HTML Metamodel];
    D -->|uses| F;

Dependencies of the project files

Now, let's see how the models are defined.

Source Metamodel

The source metamodel is defined using Emfatic (.emf), which can be converted into an ECore file. You can then access the flowchart classes as EPackages (ECore has EClasses which are referenced as EPackage in Groovy) to be used within the MT definition.

@namespace(uri="flowchart", prefix="flowchart")
package flowchart;

abstract class NamedElement {
    attr String name;
}

class Flowchart extends NamedElement {
   val Node[*] nodes;
   val Transition[*] transitions;
}

abstract class Node extends NamedElement {
   ref Transition[*]#source outgoing;
   ref Transition[*]#target incoming;
}

class Transition extends NamedElement {
   ref Node#outgoing source;
   ref Node#incoming target;
}

class Action extends Node {

}

class Decision extends Node {

}

class Subflow extends Flowchart, Node {

}

Target Metamodel

Just like before, the target metamodel is also defined using Emfatic. The metamodel script is long because all HTML elements must be defined so that the transformation generates a valid HTML document.

package HTML;

  class HTML {
    !ordered val HEAD#html head;
    !ordered val BODY#html body;
  }

  class HTMLElement {
    !unique !ordered attr EString value;
    !ordered val HTMLElement[*] children;
  }

  class HEAD extends HTMLElement {
    !ordered val HEADElement[*]#head headElements;
    !ordered ref HTML#head html;
  }

  abstract class HEADElement extends HTMLElement {
    !ordered ref HEAD#headElements head;
  }

  class LINK extends HEADElement {
    !unique !ordered attr EString rel;
    !unique !ordered attr EString title;
    !unique !ordered attr EString ahref;
    !unique !ordered attr EString type;
  }

  class TITLE extends HEADElement {
  }

  class BODY extends HTMLElement {
    !unique !ordered attr EString background;
    !unique !ordered attr EString bgcolor;
    !unique !ordered attr EString text;
    !unique !ordered attr EString link;
    !unique !ordered attr EString alink;
    !unique !ordered attr EString vlink;
    !ordered val BODYElement[*] bodyElements;
    !ordered ref HTML#body html;
  }

  abstract class BODYElement extends HTMLElement {
  }

  class H1 extends BODYElement {
  }

  class H2 extends BODYElement {
  }

  class H3 extends BODYElement {
  }

  class H4 extends BODYElement {
  }

  class EM extends BODYElement {
  }

  class STRONG extends BODYElement {
  }

  class B extends BODYElement {
  }

  class I extends BODYElement {
  }

  class TT extends BODYElement {
  }

  class PRE extends BODYElement {
  }

  class BIG extends BODYElement {
  }

  class SMALL extends BODYElement {
  }

  class SUB extends BODYElement {
  }

  class SUP extends BODYElement {
  }

  class STRIKE extends BODYElement {
  }

  class FONT extends BODYElement {
    !unique !ordered attr EString color;
    !unique !ordered attr EString face;
    !unique !ordered attr EString size;
  }

  class IMG extends BODYElement {
    !unique !ordered attr EString src;
    !unique !ordered attr EString width;
    !unique !ordered attr EString height;
    !unique !ordered attr EString alt;
    !unique !ordered attr EString align;
    !unique !ordered attr EString vspace;
    !unique !ordered attr EString hspace;
    !unique !ordered attr EString ismap;
    !unique !ordered attr EString usemap;
    !unique !ordered attr EString border;
  }

  class BR extends BODYElement {
    !unique !ordered attr EString clear;
  }

  class MAP extends BODYElement {
  }

  class AREA extends BODYElement {
    !unique !ordered attr EString shape;
    !unique !ordered attr EString coords;
    !unique !ordered attr EString ahref;
  }

  class STYLE extends BODYElement {
  }

  class EMBED extends BODYElement {
    !unique !ordered attr EString src;
    !unique !ordered attr EString width;
    !unique !ordered attr EString height;
    !unique !ordered attr EString align;
    !unique !ordered attr EString vspace;
    !unique !ordered attr EString hspace;
    !unique !ordered attr EString border;
  }

  class NOEMBED extends BODYElement {
  }

  class SPAN extends BODYElement {
    !unique !ordered attr EString style;
  }

  class A extends BODYElement {
    !unique !ordered attr EString ahref;
    !unique !ordered attr EString name;
    !unique !ordered attr EString ~id;
  }

  class DIV extends BODYElement {
    !unique !ordered attr EString align;
  }

  class P extends BODYElement {
  }

  abstract class TABLEElement extends BODYElement {
    !unique !ordered attr EString bgcolor;
    !unique !ordered attr EString background;
  }

  class TABLE extends TABLEElement {
    !unique !ordered attr EString border;
    !unique !ordered attr EString width;
    !unique !ordered attr EString cellspacing;
    !unique !ordered attr EString cellpadding;
    !ordered val TR[*]#table trs;
  }

  class TR extends TABLEElement {
    !unique !ordered attr EString valign;
    !unique !ordered attr EString align;
    !ordered ref TABLE#trs table;
    !ordered val TD[*]#tr tds;
  }

  class TD extends TABLEElement {
    !unique !ordered attr EString colspan;
    !unique !ordered attr EString rowspan;
    !unique !ordered attr EString valign;
    !unique !ordered attr EString align;
    !unique !ordered attr EString width;
    !ordered ref TR#tds tr;
  }

  class TH extends TD {
  }

  class FORM {
    !unique !ordered attr EString action;
    !unique !ordered attr EString method;
  }

  class INPUT {
    !unique !ordered attr EString align;
    !unique !ordered attr EString maxlength;
    !unique !ordered attr EString size;
    !unique !ordered attr EString checked;
    !unique !ordered attr EString src;
    !unique !ordered attr EString inputValue;
    !unique !ordered attr EString name;
    !unique !ordered attr EString type;
  }

  class TEXTAREA {
    !unique !ordered attr EString name;
    !unique !ordered attr EString rows;
    !unique !ordered attr EString cols;
  }

  class SELECT {
    !unique !ordered attr EString multiple;
    !unique !ordered attr EString size;
    !unique !ordered attr EString name;
  }

  class OPTION {
    !unique !ordered attr EString selected;
    !unique !ordered attr EString optionValue;
  }

  abstract class ListElement {
    !unique !ordered attr EString type;
  }

  class OL extends ListElement {
    !unique !ordered attr EString start;
  }

  class UL extends ListElement {
  }

  class LI extends ListElement {
    !unique !ordered attr EString liValue;
  }

  class DL {
  }

  class DT {
  }

  class DD {
  }

  class APPLET {
    !unique !ordered attr EString applet;
    !unique !ordered attr EString ~class;
    !unique !ordered attr EString src;
    !unique !ordered attr EString align;
    !unique !ordered attr EString width;
    !unique !ordered attr EString height;
  }

  class PARAM {
    !unique !ordered attr EString name;
    !unique !ordered attr EString paramValue;
  }

  class OBJECT {
    !unique !ordered attr EString classid;
    !unique !ordered attr EString ~id;
    !unique !ordered attr EString data;
    !unique !ordered attr EString type;
    !unique !ordered attr EString standby;
  }

  class FRAMESET {
    !unique !ordered attr EString rows;
    !unique !ordered attr EString cols;
    !unique !ordered attr EString framespacing;
    !unique !ordered attr EString frameborder;
    !unique !ordered attr EString border;
  }

  class FRAME {
    !unique !ordered attr EString src;
    !unique !ordered attr EString name;
    !unique !ordered attr EString marginwidth;
    !unique !ordered attr EString marginheight;
    !unique !ordered attr EString scrolling;
    !unique !ordered attr EString noresize;
  }

  class NOFRAME {
  }

  class IFRAME extends FRAME {
  }

// Based on https://github.com/SATToSE/SoTeSoLa2012/blob/master/hackathon/modisco-eclipse/org.eclipse.gmt.modisco.tool.metricsvisualizationbuilder/Metamodels/HTML.ecore

Source Model

A sample source model representing the flowchart (can be altered in an MTL solution) in Flexmi format is as follows:

<flowchart>
    <action name="Wake up" incoming="some time passes, start" outgoing=""/>
    <decision name="Is it too early?" incoming="" outgoing="yes, no"/>
    <action name="Sleep" incoming="yes" outgoing="some time passes"/>
    <action name="Get up" incoming="no"/>
    <action name="begin" outgoing="start"/>
    <transition source="Wake up" target="Is it too early?"/>
    <transition name="yes" source="Is it too early?" target="Sleep"/>
    <transition name="some time passes" source="Sleep" target="Wake up"/>
    <transition name="no" source="Is it too early?" target="Get up"/>
    <transition name="start" source="begin" target="Wake up"/>
</flowchart>

Target Model

Since the problem is open-ended there is no one solution i.e. no final target model to achieve. Check out the MTL Solutions below to see the advanced functionalities (special operations and concepts) of each MTL.

MTL Solutions

• ETL
• YAMTL

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Last update: October 13, 2023