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SWISH: A web based SWI-Prolog environment

There are three ways to use SWISH, which we list in increasing order of complexity:

  1. Use the online version
  2. Deploy the Docker image
  3. Install locally

Online versions

SWISH can be used to access SWI-Prolog at the address below. We try to keep this server continuously online. You can use these servers for playing, courses or sharing and discussing ideas.

We have not yet dealt with scalable hosting nor with really reliable and scalable storage for saved programs. We hope to keep all your programs online for at least multiple years.

Docker image

We maintain Docker images at the swipl organization at Docker Hub. A bluffer's guide to run SWISH with R if you have Docker installed is as simple as this:

docker run -d --net=none --name=rserve swipl/rserve
docker run -d -p 3050:3050 --volumes-from rserve -v $(pwd):/data swipl/swish

There are many configuration options for SWISH, notably for authentication, email notifications and extension plugins. See the docker-swish repo for details.

Local installation

Get submodules

cd to your swish root directory and run

git submodule update --init

If you have make installed you can configure the desired packs by editing the PACKS variable and run the following to download them and configure those that need to be configured.

make packs

Get JavaScript requirements

Using Yarn

Install Yarn for your platform. On Ubuntu, this implies getting node and npm by installing two packages and next use npm to install yarn (some older Linux versions need nodejs-legacy instead of nodejs):

sudo apt install npm nodejs
sudo npm i yarn -g

Once you have yarn, run the following from the toplevel of swish to get the dependencies:

yarn
make src

Download as zip

As installing node and yarn is not a pleasure on all operating systems, you can also download the dependencies as a single zip file from http://www.swi-prolog.org/download/swish/swish-node-modules.zip. Unpack the zip file, maintaining the directory structure, from the swish root directory to create the directory web/node_modules. If you have make installed you can install the above .zip file using

make yarn-zip

Last updated: Dec 16, 2019: upgraded dependencies, new archive name

Get the latest SWI-Prolog

Install the latest SWI-Prolog development version. As SWISH is very much in flux and depends on the recent SWI-Prolog pengines and sandboxing libraries, it is quite common that you need the nightly build (Windows) or build the system from the current git development repository swipl-devel.git.

Apr 25, 2019: Works for a quite large range of SWI-Prolog versions. The current swipl-devel.git snapshot fixes an issue in CSV downloading, emitting CORS and cache control HTTP headers near the end of the CSV output.

Other dependencies

Rendering Prolog terms as graphs requires Graphviz. The avatar system requires the convert utility from ImageMagic. These are available as packages for virtually any Linux system, e.g., on Debian based systems do

sudo apt-get install imagemagick
sudo apt-get install graphviz

Running SWISH

With a sufficiently recent Prolog installed, start the system by opening run.pl either by running swipl run.pl (Unix) or opening run.pl from the Windows explorer.

Now direct your browser to http://localhost:3050/

If you want to know what the latest version looks like, go to https://swish.swi-prolog.org/

Configuring SWISH

There is a lot that can be configured in SWISH. Roughly:

Configuration is done by reading *.pl files from the directory config-enabled. The directory config-available contains templates that can be copied and optionally edited to create a configuration.

See README.md in config-available for details.

Running SWISH without sandbox limitations

By default, SWISH does not require the user to login but lets you run only safe commands. If you want to use SWISH for unrestricted development, enable the config file auth_http_always.pl:

mkdir -p config-enabled
(cd config-enabled && ln -s ../config-available/auth_http_always.pl)

Next, for first usage, you need to create a user. The authentication module defines swish_add_user/0, which asks for details about the user to be created and updates or creates a file called passwd. At the moment Group and E-Mail are stored, but not used.

?- swish_add_user.
% Password file: /home/jan/src/prolog/swish/passwd (update)
User name: bob
Real name: Bob Hacker
Group:     user
E-Mail:    bob@hacker.org
Password:
(again):
true.

If you now try to run a command in SWISH, it will prompt for a user and password. After authentication you can run any Prolog predicate.

NOTE Authentication uses HTTP digest authentication by default. This authentication method uses a challenge-response method to verify the password and ensures the credentials change with every request such that old credentials cannot be re-used by an attacker. Unfortunately, the server stores the password as the SHA1 hash created from the user, password and realm. This is relatively vulnerable to brute-force attacks for anyone who gains access to the password file due to the low computational overhead of SHA1 and the lack of a user-specific salt. Also note that the exchanged commands and replies are not encrypted. Secure servers should use HTTPS.

Optional login

Instead of using auth_http_always.pl you can use auth_http.pl, which allows for unauthenticated -sandboxed- usage as well as logging in to the server and get unrestricted access. In addition, several social login modules are provided to login using Google, etc. Currently these provide no additional rights. A more fine grained authorization scheme is planned.

Running as a service

The script daemon.pl is provided to run SWISH as a service or daemon on Unix systems. Run this to get an overview of the options.

./daemon.pl --help

This script can be used to start SWISH as a daemon from the command line, start SWISH from service managers such as upstart or systemd and simplifies running as an HTTPS server. See https://github.com/triska/letswicrypt.

Running SWISH as additional local IDE

You can run SWISH alongside your normal Prolog development tools. The cleanest way to do so is by using myswish.pl and install this in your local Prolog library. See myswish.pl for details on how to set this up.

Design

Most of the application is realised using client-side JavaScript, which can be found in the directory web/js. The JavaScript files use RequireJS for dependency tracking and jQuery for structuring the JavaScript as jQuery plugins. The accompanying CSS is in web/css. More details about the organization of the JavaScript is in web/js/README.md

There are two overal pages. web/swish.html provides a static page and lib/page.pl provides a Prolog frontend to generate the overal page or parts thereof dynamically. The latter facilitates smoothless embedding in SWI-Prolog web applications.

Development and debugging

No building is needed to run the system from sources. For public installations you probably want to create the minified JavaScript and CSS files to reduce network traffic and startup time. You need some more tools for that:

% sudo npm install -g jsdoc
% sudo npm install -g requirejs
% sudo npm install -g clean-css-cli
% sudo npm install -g uglify-js

You also need GNU make installed as make and SWI-Prolog as swipl. With all that in place, the following command creates the minified versions:

% make min

The default main page (/) is generated from lib/page.pl. It uses minified JavaScript and CSS from web/js/swish-min.js web/css/swish-min.css when available. If the minified files are not present, the server automatically includes the full source. The generated files may be removed using

make clean

Alternatively, use of the minified files can be disable from Prolog using this command and reloading the page:

?- debug(nominified).

Documentation

The JavaScript is documented using JsDoc. The generated documentation is available in web/js/doc/index.html.