Modelica to JSON parser

Content

1. General Description
2. Installation and help
3. How to use the parser
4. JSON Schemas
5. Useful Links

1. General Description

modelica-json is a translator that parses the Modelica language to JSON. Two translation modes have been implemented : The first mode aims to parse Modelica packages and takes into input a directory of .mo files. The other mode aims to parse CDL files and takes a single .mo file compliant with the CDL language as input. For more information on the CDL Language, please refer to the OpenBuildingControl project website.

See the directory test/FromModelica from modelica-json for simple examples from Modelica and CDL to detailed and simplified JSON.

2. Installation and help

Linux

First, set the MODELICAPATH environment variable by adding the following line to your ~/.bashrc file:

export MODELICAPATH=${MODELICAPATH}:/usr/local/Modelica/Library/

The parser requires Java and node. The java dependency can be installed using:

sudo apt-get install default-jdk default-jre

The node version should be >= 18 and you can use Node Version Manager to set it up. Following is using 0.39.7 version:

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh | bash
source ~/.bashrc
nvm install 18

To install dependencies of the parser, run

make install

To compile the Java files, run

make compile

To run the test cases, run

npm test

To get more help, run

node app.js -h

To clean the current installation, run

make clean-installation

Windows

• First, make sure that both the modelica-json directory and the Modelica Buildings Library directory are in the folders that do not require administrator access. By saving the directories in driver other than C:\ would typical avoid the administrator access issue.

• Then, create the MODELICAPATH environment variable and set the value as the path of Modelica Buildings Library, like E:\modelica-buildings or E:\modelica-buildings-master.

• Install Java SE Development Kit (64-bit version), Java Runtime Environment (64-bit version) and Node.js.

• Add path\to\your\nodejs to the Path environment.

• In batch file InstallOnWindows.bat, update JAVA_HOME path in line set JAVA_HOME=path\to\your\jdk.

• Finally, to install dependencies and compile the Java files, run InstallOnWindows.bat.

To test the installation, from the \modelica-json directory, run the parser on Command Prompt:

node app.js -f test\FromModelica\Enable.mo

Now the \modelica-json directory should have a new folder json and in the folder, there should be a file in the path test\FromModelica\Enable.json.

3. How to use the parser

The parser can be run with the app.js file as follows:

node app.js -f <path of the file to parse>

Arguments :

--file / -f

The only required input is the path of the file or package to be parsed.

--output / -o

This parser takes a .mo file in input and has three possible outputs, that can be specified with the argument -o :

• raw-json : detailed transcription of a Modelica file in JSON
• json: simplified JSON format, easier to read an interpret
• semantic: generate semantic model from semantic information included within annotation in the Modelica file
• cxf: generate CXF representation in .jsonld of a CDL sequence complying with ASHRAE S231P

--mode / -m

We offer two different modes of translation that can be chosen with the argument -m :

• modelica : Parses a Modelica package (must be a directory)
• cdl (default) : Parses a CDL file.

--log / -l

Logging level. The choices are error, warn, info (default), verbose, debug.

--directory / -d

Specify the output directory. The default option is the current directory.

--prettyPrint / -p

If -p flag is specified, the JSON output conforms to prettyprint. The default option is false.

--elementary

If --elementary flag is specified, the CXF (jsonld) files for the elementary blocks are also generated. Else, they are ignored. The default option is false. -o/--output should be cxf.

--cxfCore

If --cxfCore flag is specified, generate the CXF-core.jsonld files for all the elementary blocks. The default option is false.
-o/--output should be cxf, -f/--file should be path/to/CDL and --elementary flag must be used.

4. JSON Schemas

The JSON representation of Modelica and CXF models must be compliant with the corresponding JSON Schema. This is applicable for the JSON and CXF output respectively.

JSON Schemas describe the data format and file structure to ensure the quality of the JSON files.

Two schemas are available (links to the raw files) :

• schema-cxf.json validates the JSON files parsed from CDL classes to form CXF representations
• schema-modelica.json validates the JSON files parsed from Modelica models

Graphical viewers are available (please use right click + open in a new tab or refresh the page if necessary - this is not optimized for Firefox) :

• CXF Schema viewer
• Modelica Schema viewer

5. CXF-Core.jsonld

CXF-Core.jsonld contains the CXF representation of all CDL elementary blocks, classes and relationships.

To generate the CXF-Core.jsonld, use:

node app.js -f <path/to/modelica-buildings>/Buildings/Controls/OBC/CDL -o cxf --elementary --cxfCore

The CXF-Core.jsonld file will be generated in cxf folder.

When parsing a file using app.js, the schema is chosen according to the mode.

To validate an existing JSON file against the schema, run

node validation.js -f <path to the json file>

The default schema is CDL. To chose the Modelica schema, run:

node validation.js -f <path to the json file> -m modelica

5. Useful Links

• Modelica-json GitHub page
• The Modelica Association
• Control Description Language
• JSON Schema

License

Modified 3-clause BSD, see LICENSE.md.

Copyright

See copyright notice.