HEX-Programs with Nested Program Calls

  • Thomas Eiter
  • Thomas Krennwallner
  • Christoph RedlEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 7773)


Answer-Set Programming (ASP) is an established declarative programming paradigm. However, classical ASP lacks subprogram calls as in procedural programming, and access to external computations (akin to remote procedure calls) in general. This feature is desired for increasing modularity and—assuming proper access in place—(meta-)reasoning over subprogram results. While hex-programs extend classical ASP with external source access, they do not support calls of (sub-)programs upfront. We present nested hex -programs, which extend hex-programs to serve the desired feature in a user-friendly manner. Notably, the answer sets of called sub-programs can be individually accessed. This is particularly useful for applications that need to reason over answer sets like belief set merging, user-defined aggregate functions, or preferences of answer sets. We will further present a novel method for rapid prototyping of external sources by the use of nested programs.


External Source Logic Program Extended Logic Program Merging Operator Host Program 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Thomas Eiter
    • 1
  • Thomas Krennwallner
    • 1
  • Christoph Redl
    • 1
    Email author
  1. 1.Institut für InformationssystemeTechnische Universität WienViennaAustria

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