Open Topics

• Constraint Handling Rules as a Library with Delimited Control

  BA/MA/Project

  Constraint Handling Rules (CHR) is a declarative, rule-based programming language. Its syntax consists of just three committed-choice multi-set transformation rules and is thus fairly simple. There are implementations and embeddings for many programming languages such as C, Java, Haskell, and JavaScript. However, CHR’s most popular host language remains Prolog. Current implementations of CHR in Prolog rely on Prolog’s implicit execution stack, others use attributed variables. In this project, we want to implement a new compilation scheme to Prolog based on delimited continuations. This takes up the idea of an explicit stack, which is a common optimisation technique when compiling CHR to imperative programming languages. Delimited continuations have already been successfully used to efficiently implement tabling in Prolog – so it might be worth considering them for CHR, too.

  • CHR
  • compiler construction
  • declarative programming
  • Prolog

• XPCE Compatibility for SWISH

  BA/MA/Project

  XPCE was the way to go for graphical user interfaces with SWI-Prolog. In recent years, with SWISH, SWI-Prolog moved to the browser as the most important GUI, leaving XPCE unsupported and almost deprecated. We want to examine typical XPCE applications and provide mechanisms to convert them to SWISH applications.

  • GUI
  • program transformation
  • Prolog

• OpenRuleBench Revised

  BA/MA/Project

  OpenRuleBench is a suite of benchmarks for analysing the performance and scalability of different rule engines. The original benchmarks were run first in 2009, an updated report was published in 2011. Since then, the benchmarks have not been re-run. In this work, we want to create an experimental setup to run various tests on different systems, similar to our CHR Benchmark suite. It should allow to validate the original results, and to re-run the tests with modern rule engines. This could result in a public test server to compare existing and new logic programming systems and their strengths.

  • benchmarks
  • declarative programming
  • Prolog

• A Controlled Natural Language for COVID Regulations

  BA/MA

  In the past two years, the Coronavirus disease COVID-19 had a strong impact on most parts of our everyday life. People had to wear masks under some conditions, like the number of persons in a group or the size of the room. These conditions have been determined by the government in more than 30 regulations. In this work, we want to tailor the corpus of these regulations towards a more controlled natural language so they can be easily used by both humans and machines, e.g., to automatically identify inconsistencies. Because the Corona-Bekämpfungsverordnung (CoBeLVO) is in German, a good knowledge of German is required.

  • controlled natural language
  • domain-specific language

• Statistische Jahresberichte auf Basis von Linked Open Data

  BA/MA/Project/Hiwi

  Viele Kommunen in Deutschland veröffentlichen jährlich einen statistischen Jahresbericht. Diese Statistiken beinhalten u.a. soziodemografische Informationen zur Bevölkerung (z.B. Alter, Familienstand), zur Wirtschaft (z.B. Gewerbesteuer, Insolvenzverfahren) und Verkehr (z.B. PKW-Neuzulassungen, Verkehrsunfälle), und zu Kultur und Sport (z.B. Bibliotheksbestand, Vereinsmitgliedschaften). Sie sind wertvolle Ratgeber für Planung, Handel und Politik. Trotz ihres großen Nutzens ist die Erstellung der oft mehrere hundert Seiten langen Jahresberichte aber noch weitestgehend Handarbeit: Statistiken werden mühevoll zusammengetragen und Visualisierungen erstellt – eine Tätigkeit, die sich durch Linked (Open) Data vollständig automatisieren ließe. Ziel dieser Arbeit ist es, am Beispiel der Stadt Kaiserslautern den statistischen Jahresbericht als Linked (Open) Data umzusetzen und eine interaktive Darstellung zu ermöglichen, die über die bisherige Druckfassung hinausgeht. Für die Materialien und Anwendungspartner sind gute Deutschkenntnisse erforderlich.

  • linked data
  • open data
  • semantic web
  • smart city
  • visualization

• Bisecting Debugger for SWI-Prolog

  BA/Project

  Although it is hard to admit: most of the time we are actually not writing code but instead debug existing. Due to its good backtracking and tracing abilities, debugging in Prolog could benefit from a bisecting debugger as described by Michael Hendricks at Strange Loop 2014. In this work we want to enhance SWI-Prolog’s built-in debugger with this functionality.

  • debugging
  • IDE
  • program transformation
  • Prolog

• A Style Linter for Prolog

  BA/MA/Project

  Although there are several style guides for Prolog, it is hard to enforce one in existing programs due to the lack of related tools and machine-readable representation. In other programming languages there are separate, flexible tools just to ensure a consistent coding style, for example Prettier or the JavaScript standard style. In this work we want to adapt these concepts and integrate a Prolog linter into CI workflows and IDEs, with respect to Prolog’s syntax, and based on our previous work.

  • coding guidelines
  • continuous integration
  • Prolog

• Benchmarking CHR Systems

  BA/Project

  Constraint Handling Rules (CHR) is a very simple but powerful rule-based language. Besides its most popular implementation as a library for SWI-Prolog, there exist CHR systems in C, Haskell, and JavaScript. More than 30 years after the creation of CHR, the existing implementations should be compared regarding supported features and performance, extending our previous work.

  • benchmarks
  • CHR
  • declarative programming

• Optimising Definite Clause Grammars

  MA/Project

  Definite Clause Grammars (DCG) can be easily written by hand and are therefore a good alternative to parser implementations based on LL(k), LF or PEG. Nevertheless, such hand-written grammars tend to be not optimal: Several parts of the parse tree have to be evaluated several times for the same expression because of its backtracking nature. Using source-to-source transformation the DCG can be rewritten into an optimal version, which should be done in Prolog as part of this work.

  • backtracking
  • compiler
  • context-free grammar
  • parser
  • program transformation
  • Prolog