2P-Kt
Some quick links:
- Home Page
- GitHub Repository (public repository)
- GitLab Repository (dismissed)
- NPM Repository (where JS releases are hosted)
- Maven Central Repository (where all stable releases are hosted)
- GitHub Maven Repository (where all releases are hosted, there including dev releases)
- Documentation (work in progress)
- Presentation (currently describing the main API of 2P-Kt)
Intro

tuProlog (2P henceforth) is a multi-paradigm
logic programming framework written in Java.
2P-Kt is a Kotlin-based and multi-platform reboot of 2P.
It consists of an open ecosystem for Symbolic Artificial Intelligence (AI).
For this reason, 2P-Kt consists of a number of incrementally inter-dependent modules aimed at supporting symbolic
manipulation and reasoning in an extensible and flexible way.
A complete overview about modules and their dependencies is provided by the following diagram:

As shown in the project map, 2P-Kt currently focuses on supporting knowledge representation and automatic reasoning through logic programming,
by featuring:
The modular, unopinionated architecture of 2P-Kt is deliberately aimed at supporting and encouraging extensions towards
other sorts of symbolic AI systems than Prolog---such as ASP, tabled-Prolog, concurrent LP, etc.
Furthermore, 2P-Kt is developed as in pure, multi-platform Kotlin project.
This brings two immediate advantages:
- it virtually supports several platforms, there including JVM, JS, Android, and Native (even if, currently, only JVM,
JS and Android are supported),
- it consists of a very minimal and lightweight library, only leveraging on the Kotlin common library, as it cannot
commit to any particular platform standard library.
Users
2P-Kt can either be used as a command-line program or as a Kotlin, JVM, Android, or JS library.
The 2P-Kt executables are currently available for download on the Releases section of the
GitHub repository.
The 2P-Kt modules for JVM, Android, or Kotlin users are currently available for import
on Maven Central, under the it.unibo.tuprolog group ID (not
to be confused with the it.unibo.alice.tuprolog, which contains the old Java-based implementation).
The same modules are available through an ad-hoc Maven repository as well,
hosted by GitHub.
The 2P-Kt modules for JS users, are available for import on NPM, under the @tuprolog organization.
End users
Graphical User Interface
If you need a GUI for your Prolog interpreter, you can rely on the 2P-Kt IDE which is available on the Releases section of the
GitHub repository.
The page of the latest release of 2P-Kt exposes a number of Assets.
There, the one named:
2p-ide-VERSION-redist.jar
is the self-contained, executable Jar containing the 2P-Kt-based Prolog interpreter (VERSION may vary depending on the
actual release version).
After you download the 2p-ide-VERSION-redist.jar, you can simply launch it by running:
java -jar 2p-ide-VERSION-redist.jar
However, if you have properly configured the JVM on your system, it may be sufficient to just double-click on the
aforementioned JAR to start the IDE.
In any case, running the JAR should make the following window appear:

There, one may query the 2P-Kt Prolog interpreter against the currently opened theory file, which can of course be
loaded from the user's file system by pressing File and then Open....
To issue a query, the user must write it in the query text field, at the center of the application.
By either pressing Enter while the cursor is on the query text field, or by clicking on the Solve
(resp. Solve all) button, the user can start a new resolution process, aimed at solving the provided query.
Further solutions can be explored by clicking on the Next (resp. All next) button over and over again.
The (resp. ) button shall appear in place of (resp. )
if and when further solutions are available for the current query.
One may also compute all the unexplored solutions at once by clicking on the Solve all
(resp. All next) button.
Avoid this option in case of your query is expected to compute an unlimited amount of solutions.
To perform a novel query, they user may either:
- write the new query in the query text field, and then press Enter, or
- click on the Stop button, write the new query in the query text field, and then press the Solve
(resp. SolveNext) button again.
The Reset button cleans up the status of the solver, clearing any side effect possibly provoked by previous
queries (including assertions, retractions, prints, warnings, loading of libraries, operators, or flags).
Finally, users may inspect the current status of the solver by leveraging the many tabs laying at the bottom of the IDE.
There,
Any of these tabs may be automatically updated after a solution to some query is computed.
Whenever something changes w.r.t. the previous content of the tab, an asterisk will appear close to the tab name, to notify an update in that tab.
Command Line Interface
If you just need a command-line Prolog interpreter, you can rely on the 2P-Kt REPL which is available on the Releases section of the
GitHub repository.
The page of the latest release of 2P-Kt exposes a number of Assets.
There, the one named:
2p-repl-VERSION-redist.jar
is the self-contained, executable Jar containing the 2P-Kt-based Prolog interpreter (VERSION may vary depending on the
actual release version).
After you download the 2p-repl-VERSION-redist.jar, you can simply launch it by running:
java -jar 2p-repl-VERSION-redist.jar
This should start an interactive read-eval-print loop accepting Prolog queries.
A normal output should be as follows:
?- <write your dot-terminated Prolog query here>.
For instance:

Other options or modes of execution are supported.
One can explore them via the program help, which can be displayed by running:
java -jar 2p-repl-VERSION-redist.jar --help
This should display a message similar to the following one:
Usage: java -jar 2p-repl.jar [OPTIONS] COMMAND [ARGS]...
Start a Prolog Read-Eval-Print loop
Options:
-T,
-t,
1000 ms)
h,
Commands:
solve Compute a particular query terminate
Gradle users
To import the 2P-Kt module named 2P_MODULE (version 2P_VERSION) into your Kotlin-based project leveraging on Gradle,
you simply need to declare the corresponding dependency in your build.gradle(.kts) file:
dependencies {
implementation("it.unibo.tuprolog", "2P_MODULE", "2P_VERSION")
}
In this way, the dependencies of 2P_MODULE should be automatically imported.
The step above, requires you to tell Gradle to either use Maven Central or our GitHub repository (or both) as a source
for dependency lookup. You can do it as follows:
repositories {
maven("https://maven.pkg.github.com/tuProlog/2p-kt")
mavenCentral()
}
Authentication may be required in case the GitHub repository is exploited
JVM-only projects with Gradle
Remember to add the -jvm suffix to 2P_MODULE in case your project only targets the JVM platform:
dependencies {
implementation("it.unibo.tuprolog", "2P_MODULE-jvm", "2P_VERSION")
}
Maven users
To import the 2P-Kt module named 2P_MODULE (version 2P_VERSION) into your Kotlin-based project leveraging on Maven,
you simply need to declare the corresponding dependency in your pom.xml file:
<dependency>
<groupId>it.unibo.tuprolog</groupId>
<artifactId>2P_MODULE</artifactId>
<version>2P_VERSION</version>
</dependency>
In this way, the dependencies of 2P_MODULE should be automatically imported.
The step above, requires you to tell Maven to either use Maven Central or our GitHub repository (or both) as a source
for dependency lookup. You can do it as follows:
<repositories>
<repository>
<id>github-2p-repo</id>
<url>https://maven.pkg.github.com/tuProlog/2p-kt</url>
</repository>
</repositories>
Authentication may be required in case the GitHub repository is exploited
JVM-only projects with Maven
Remember to add the -jvm suffix to 2P_MODULE in case your project only targets the JVM platform:
<dependency>
<groupId>it.unibo.tuprolog</groupId>
<artifactId>2P_MODULE-jvm</artifactId>
<version>2P_VERSION</version>
</dependency>
NPM users (JavaScript-only projects)
The 2P-Kt software is available as a JavaScript library as well, on NPM, under the @tuprolog organization.
To import the 2P_MODULE into your package.json, it is sufficient to declare your dependency as follows:
{
"dependencies": {
"@tuprolog/2P_MODULE": "^2P_MODULE_VERSION"
}
}
Notice that the JS dependencies of 2P_MODULE should be automatically imported.
Developers
Working with the 2P-Kt codebase requires a number of tools to be installed and properly configured on your system:
- JDK 11+ (please ensure the
JAVA_HOME environment variable is properly) configured
- Kotlin 1.5.10+
- Gradle 7.1+ (please ensure the
GRADLE_HOME environment variable is properly configured)
- Git 2.20+
Develop 2P-Kt with IntelliJ Idea
To participate in the development of 2P-Kt, we suggest the IntelliJ Idea IDE.
The free, Community version will be fine.
Recommended configuration
You will need the Kotlin plugin for IntelliJ Idea.
This is usually installed upon Idea's very first setup wizard.
However, one may easily late-install such plugin through the IDE's Plugins settings dialog.
To open such dialog, use Ctrl+Shift+A, then search for "Plugins"
Importing the project
Developing the project
Contributions to this project are welcome. Just some rules:
-
We use , so if you write new features, please do so in a separate branch
Building the project
While developing, you can rely on IntelliJ to build the project, it will generally do a very good job.
If you want to generate the artifacts, you can rely on Gradle. Just point a terminal on the project's root and issue
./gradlew build
This will trigger the creation of the artifacts the executions of the tests, the generation of the documentation and of the project reports.
Versioning
The 2P project leverages on Semantic Versioning (SemVer, henceforth).
In particular, SemVer is enforced by the current Gradle configuration, which features DanySK's Git sensitive SemVer Gradle Plugin.
This implies it is strictly forbidden in this project to create tags whose label is not a valid SemVar string.
Notice that the 2P project is still in its initial development stage---as proven by the major number equal to 0 in its version string.
According to SemVer, this implies anything may change at any time, as the public API should not be considered stable.
Issue tracking
If you meet some problem in using or developing 2P, you are encouraged to signal it through the project "Issues" section on GitHub.