The Participatory System Mapper (PRSM for short) is an app that runs in a web browser that makes it easy for a group of people working together to draw networks (or 'maps') of systems.

The network or map can be anything that has items (or 'factors' or 'nodes') connected by links (or 'edges'). Here are some examples:

• People (the nodes) connected by knowing each other
• Factors or variables causing (the links) changes in other factors
• Switches connected by wires
• Computers connected by network links
• Theories expressed as variables and relationships between them
• Company boards of directors (the nodes) and the directors that sit on more than one board (the links)
• Twitter hashtags (the nodes) included together on posts (the links)
• Scientists (the nodes) co-authoring papers (the links)
• and so on.

The app is designed to enable groups of people, each using their own computer (or tablet) to collaborate in the drawing of a map. They may be sitting around a table, discussing the map as it is created face to face, or working remotely, using video conferencing or the chat feature that is built into the app. Everyone can participate because every edit (creating nodes and links, arranging them and so on) is broadcast to all the other participants as the changes are made (just as Google Docs does for text, for example).

When you start the app in your browser, a 'room' is created for you in which to draw your network. You can add other users to this room to share the work. Only those with access to the room can see what is being created.

For more on PRSM, see here. A guide to using PRSM is here.

No installation on your computer is needed. The software is a web app, which means that it can be accessed using a web browser by pasting this link into the address bar:

https://prsm.uk/prsm.html

You need a modern web browser such as Chrome, Firefox, Microsoft Edge or Safari. It will not work with Internet Explorer.

The software is free and available under an MIT license.

The program code is available on GitHub.

The javascript (ES6) code in sub-directory js is divided into modules:

• prsm.js handles the main network pane
• background.js manages drawing objects on the background
• styles.js creates and edits the styles
• the default styles are in samples.js
• files.js does the import and export functions
• cluster.js clusters factors
• table.js provides the data view
• trophic.js does the trophic layout algorithm
• betweenness.js is a web worker that cacilates network statistics in the background
• tutorial.js manages the initial tour
• utils.js includes utility functions common to several modules
• merge.js provides undocumented functions to merge two maps into one

The HTML files that display in the browser are in the html directory.

PRSM uses two important packages: yjs and vis-network. The former handles the sharing between participants' browsers and the latter draws the network. A few other packages are used for dealing with touch input (Hammer), drawing emojis, and parsing XML file input.

These components are assembled using parcel and the bundled files are placed in the dist directory. So that users have an easy URL to access (i.e. not needing to include dist in the link), there is an .htaccess file that rewrites URLs from what the user puts into their browser to the correct location.

To install the code, use git to clone the repo to your local disk and change to the cloned directory. Then install the required packages with

npm install

and build the distribution with

npm run build

The Apache2 headers module must be enabled. If the installation isn't visible in your browser this is likely the cause. Enabling the module is simple on Debian/Ubuntu systems:

sudo a2enmod headers
systemctl restart apache2

Documentation can be found in the doc directory.

See package.json for other npm commands.

With thanks to all who helped inspire, suggest features for, comment on, and test PRSM, including the members of CECAN, CRESS, Risk Solutions, and Robin Gilbert.

Please report problems, suggestions and praise to [email protected]