T. Eiter, T. Krennwallner, C. Redl:
"HEX-Programs with Nested Program Calls";
in: "19th International Conference on Applications of Declarative Programming and Knowledge Management (INAP 2011) and 25th Workshop on Logic Programming (WLP 2011)", H. Tompits, S. Abreu, J. Oetsch, J. Puehrer, D. Seipel, M. Umeda, A. Wolf (ed.); Springer, Heidelberg, 2013, ISBN: 978-3-642-41523-4, 269 - 278.

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.

http://dx.doi.org/10.1007/978-3-642-41524-1_15

Project Head Thomas Eiter:
Evaluierung von ASP Programming mit Externen Zugriffen

Project Head Thomas Eiter:
Modulare HEX-Programme