## Members

## Bruno Buchberger

## David Cerna

## Tudor Jebelean

## Zoltán Kovács: joint PostDoc GeoGebra+RISC

## Teimuraz Kutsia

## Alexander Maletzky

## Nikolaj Popov

## Jakob Praher

## Markus Rosenkranz

## Wolfgang Schreiner

## Wolfgang Windsteiger

## Ongoing Projects

### Logic Technology for Computer Science Education [LOGTECHEDU]

### Combinatorics and Codes for Information Security [SBA-K1]

### Theory Exploration in Theorema: Recent Approaches to Gröbner Bases [TETRA-GB]

## Software

PρLog (pronounced Pē-rō-log) is an experimental tool that extends logic programming with strategic conditional transformation rules, combining Prolog with ρLog calculus. It deals with term sequences (also called hedges), transforming them by conditional rules. Transformations are nondeterministic and may yield ...

The present prototype version of the Theorema software system is implemented in Mathematica . The system consists of a general higher-order predicate logic prover and a collection of special provers that call each other depending on the particular proof situations. ...

## Publications

### 2019

### On the Complexity of Unsatisfiable Primitive Recursively defined $\Sigma_1$-Sentences

#### David M. Cerna

In: T.B.D, T.B.D (ed.), Proceedings of T.B.D, pp. 1-17. 2019. T.B.D. [pdf]**inproceedings**{RISC5841,

author = {David M. Cerna},

title = {{On the Complexity of Unsatisfiable Primitive Recursively defined $\Sigma_1$-Sentences}},

booktitle = {{T.B.D}},

language = {english},

abstract = {We introduce a measure of complexity based on formula occurrence within instance proofs of an inductive statement. Our measure is closely related to {\em Herbrand Sequent length}, but instead of capturing the number of necessary term instantiations, it captures the finite representational difficulty of a recursive sequence of proofs. We restrict ourselves to a class of unsatisfiable primitive recursively defined negation normal form first-order sentences, referred to as {\em abstract sentences}, which capture many problems of interest; for example, variants of the {\em infinitary pigeonhole principle}. This class of sentences has been particularly useful for inductive formal proof analysis and proof transformation. Together our complexity measure and abstract sentences allow use to capture a notion of {\em tractability} for state-of-the-art approaches to inductive theorem proving, in particular {\em loop discovery} and {\em tree grammar} based inductive theorem provers. We provide a complexity analysis of an important abstract sentence, and discuss the analysis of a few related sentences, based on the infinitary pigeonhole principle which we conjecture represent the upper limits of tractability and foundation of intractability with respect to the current approaches.},

pages = {1--17},

isbn_issn = {T.B.D},

year = {2019},

editor = {T.B.D},

refereed = {yes},

length = {17},

conferencename = {T.B.D}

}

### A Generic Framework for Higher-Order Generalizations

#### David M. Cerna, Temur Kutsia

Technical report no. 19-01 in RISC Report Series, Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz, Schloss Hagenberg, 4232 Hagenberg, Austria. 2019. [pdf]**techreport**{RISC5883,

author = {David M. Cerna and Temur Kutsia},

title = {{A Generic Framework for Higher-Order Generalizations}},

language = {english},

number = {19-01},

year = {2019},

length = {21},

type = {RISC Report Series},

institution = {Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz},

address = {Schloss Hagenberg, 4232 Hagenberg, Austria}

}

### Evaluation of the VL Logic (342.208-9) 2018W End of Semester Questionnaire

#### David M. Cerna

Feburary 2019. [pdf] [xlsx]**techreport**{RISC5885,

author = {David M. Cerna},

title = {{Evaluation of the VL Logic (342.208-9) 2018W End of Semester Questionnaire}},

language = {english},

abstract = {In this technical report we cover the choice of layout and intentions behind our end of the semester questionnaire as well as our interpretation of student answers, resulting statistical analysis, and inferences. Our questionnaire is to some extent free-form in that we provide instructions concerning the desired content of the answers but leave the precise formulation of the answer to the student. Our goal, through this approach, was to gain an understanding of how the students viewed there own progress and interest in the course without explicitly guiding them. Towards this end, we chose to have the students draw curves supplemented by short descriptions of important features. We end with a discussion of the benefits and downsides of such a questionnaire as well as what the results entail concerning future iterations of the course. },

year = {2019},

month = {Feburary},

length = {17},

type = {RISC Report Series},

institution = {Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz},

address = {Schloss Hagenberg, 4232 Hagenberg, Austria}

}

### The Castle Game

#### David M. Cerna

2019. [pdf]**techreport**{RISC5886,

author = {David M. Cerna},

title = {{The Castle Game}},

language = {english},

abstract = {A description of a game for teaching certain aspects of first-order logic based on the Drink's Paradox. },

year = {2019},

length = {3},

type = {RISC Report Series},

institution = {Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz},

address = {Schloss Hagenberg, 4232 Hagenberg, Austria}

}

### Manual for AXolotl

#### David M. Cerna

2019. [jar] [zip] [pdf]**techreport**{RISC5887,

author = {David M. Cerna},

title = {{Manual for AXolotl}},

language = {english},

abstract = {In this document we outline how to play our preliminary version of \textbf{AX}olotl. We present a sequence of graphics illustrating the step by step process of playing the game. },

year = {2019},

length = {9},

type = {RISC Report Series},

institution = {Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz},

address = {Schloss Hagenberg, 4232 Hagenberg, Austria}

}

### Higher-Order Pattern Generalization Modulo Equational Theories

#### David M. Cerna and Temur Kutsia

2019. [pdf]**techreport**{RISC5918,

author = {David M. Cerna and Temur Kutsia},

title = {{Higher-Order Pattern Generalization Modulo Equational Theories}},

language = {english},

abstract = {We consider anti-unification for simply typed lambda terms in theories defined by associativity,commutativity, identity (unit element) axioms and their combinations, and develop a sound andcomplete algorithm which takes two lambda terms and computes their equational generalizations inthe form of higher-order patterns. The problem is finitary: the minimal complete set of suchgeneralizations contains finitely many elements. We define the notion of optimal solution andinvestigate special fragments of the problem for which the optimal solution can be computed in linearor polynomial time.},

year = {2019},

length = {25},

type = {RISC Report Series},

institution = {Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz},

address = {Schloss Hagenberg, 4232 Hagenberg, Austria}

}

### Theorem and Algorithm Checking for Courses on Logic and Formal Methods

#### Wolfgang Schreiner

In: Post-Proceedings ThEdu'18, Pedro Quaresma and Walther Neuper (ed.), Proceedings of 7th International Workshop on Theorem proving components for Educational software, Oxford, United Kingdom, 18 July 2018, Electronic Proceedings in Theoretical Computer Science (EPTCS) 290, pp. 56-75. April 1 2019. Open Publishing Association, ISSN 2075-2180. [url] [pdf]**inproceedings**{RISC5895,

author = {Wolfgang Schreiner},

title = {{Theorem and Algorithm Checking for Courses on Logic and Formal Methods}},

booktitle = {{Post-Proceedings ThEdu'18}},

language = {english},

abstract = {The RISC Algorithm Language (RISCAL) is a language for the formal modeling of theories and algorithms. A RISCAL specification describes an infinite class of models each of which has finite size; this allows to fully automatically check in such a model the validity of all theorems and the correctness of all algorithms. RISCAL thus enables us to quickly verify/falsify the specific truth of propositions in sample instances of a model class before attempting to prove their general truth in the whole class: the first can be achieved in a fully automatic way while the second typically requires our assistance. RISCAL has been mainly developed for educational purposes. To this end this paper reports on some new enhancements of the tool: the automatic generation of checkable verification conditions from algorithms, the visualization of the execution of procedures and the evaluation of formulas illustrating the computation of their results, and the generation of Web-based student exercises and assignments from RISCAL specifications. Furthermore, we report on our first experience with RISCAL in the teaching of courses on logic and formal methods and on further plans to use this tool to enhance formal education.},

series = {Electronic Proceedings in Theoretical Computer Science (EPTCS)},

volume = {290},

pages = {56--75},

publisher = {Open Publishing Association},

isbn_issn = {ISSN 2075-2180},

year = {2019},

month = {April 1},

editor = {Pedro Quaresma and Walther Neuper},

refereed = {yes},

sponsor = {Linz Institute of Technology (LIT), Project LOGTECHEDU “Logic Technology for Computer Science Education” and OEAD WTZ project SK 14/2018 SemTech},

length = {20},

conferencename = {7th International Workshop on Theorem proving components for Educational software, Oxford, United Kingdom, 18 July 2018},

url = {http://dx.doi.org/10.4204/EPTCS.290.5}

}

### A Categorical Semantics of Relational First-Order Logic

#### Wolfgang Schreiner, Valerie Novitzká, William Steingartner

Research Institute for Symbolic Computation (RISC), Johannes Kepler University, Linz, Austria. Technical report, March 2019. [pdf]**techreport**{RISC5900,

author = {Wolfgang Schreiner and Valerie Novitzká and William Steingartner},

title = {{A Categorical Semantics of Relational First-Order Logic}},

language = {english},

abstract = {We present a categorical formalization of a variant of first-order logic. Unlike other textson this topic, the goal of this paper is to give a very transparent and self-contained accountwithout requiring more background than basic logic and set theory. Our focus is to showhow the semantics of first order formulas can be derived from their usual deduction rules.For understanding the core ideas, it is not necessary to investigate the internal term structureof atomic formulas, thus we abstract atomic formulas to (syntactically opaque) relations;in this sense our variant of first-order logic is “relational”. While the derived semanticsis based on categorical principles, it is nevertheless “constructive” in that it describesexplicit computations of the truth values of formulas. We demonstrate this by modeling thecategorical semantics in the RISCAL (RISC Algorithm Language) system which allows usto validate the core propositions by automatically checking them in finite models.},

year = {2019},

month = {March},

institution = {Research Institute for Symbolic Computation (RISC), Johannes Kepler University, Linz, Austria},

keywords = {first-order logic, formal semantics, category theory, RISC Algorithm Language (RISCAL)},

sponsor = {OEAD WTZ project SK 14/2018 “SemTech — Semantic Technologies for Computer Science Education” and JKU LIT project LOGTECHEDU “Logic Technology for Computer Science Education”},

length = {34}

}

### 2018

### Anti-Unification and Natural Language Processing

#### N. Amiridze, T. Kutsia

In: Fifth Workshop on Natural Language and Computer Science, NLCS’18, A. Asudeh, V. de Paiva, L. Moss (ed.), EasyChair preprints 203, pp. 1-12. 2018. [url] [pdf]**inproceedings**{RISC5707,

author = {N. Amiridze and T. Kutsia},

title = {{Anti-Unification and Natural Language Processing}},

booktitle = {{Fifth Workshop on Natural Language and Computer Science, NLCS’18}},

language = {english},

series = {EasyChair preprints},

number = {203},

pages = {1--12},

isbn_issn = { },

year = {2018},

editor = {A. Asudeh and V. de Paiva and L. Moss},

refereed = {yes},

length = {12},

url = {https://doi.org/10.29007/fkrh}

}

### Term-Graph Anti-Unification

#### Alexander Baumgartner, Temur Kutsia, Jordi Levy, Mateu Villaret

Technical report no. 18-02 in RISC Report Series, Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz, Schloss Hagenberg, 4232 Hagenberg, Austria. 2018. [pdf]**techreport**{RISC5549,

author = {Alexander Baumgartner and Temur Kutsia and Jordi Levy and Mateu Villaret},

title = {{Term-Graph Anti-Unification}},

language = {english},

number = {18-02},

year = {2018},

length = {19},

type = {RISC Report Series},

institution = {Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz},

address = {Schloss Hagenberg, 4232 Hagenberg, Austria}

}

### Idempotent Anti-unification

#### David M. Cerna Temur Kutsia

RISC. Technical report, Feb. 2018. Submitted for review. [pdf]**techreport**{RISC5530,

author = {David M. Cerna Temur Kutsia},

title = {{Idempotent Anti-unification }},

language = {english},

abstract = {In this paper we address two problems related to idempotent anti-unification. First, we show thatthere exists an anti-unification problem with a single idempotent symbol which has an infiniteminimal complete set of generalizations. It means that anti-unification with a single idempotentsymbol has infinitary or nullary generalization type, similar to anti-unification with two idem-potent symbols, shown earlier by Loı̈c Pottier. Next, we develop an algorithm, which takes anarbitrary idempotent anti-unification problem and computes a representation of its solution set inthe form of a regular tree grammar. The algorithm does not depend on the number of idempotentfunction symbols in the input terms. The language generated by the grammar is the minimalcomplete set of generalizations of the given anti-unification problem, which implies that idem-potent anti-unification is infinitary.},

year = {2018},

month = {Feb.},

note = {Submitted for review},

institution = {RISC},

length = {27}

}

### Primitive Recursive Proof Systems for Arithmetic

#### David M. Cerna

RISC. Technical report, January 2018. In revision. [pdf]**techreport**{RISC5528,

author = {David M. Cerna},

title = {{Primitive Recursive Proof Systems for Arithmetic}},

language = {english},

abstract = {Peano arithmetic, as formalized by Gentzen, can be presented as an axiom extensionof the LK-calculus with equality and an additional inference rule formalizing induction.While this formalism was enough (with the addition of some meta-theoretic argumentation)to show the consistency of arithmetic, alternative formulations of induction such asthe infinitary ω-rule and cyclic reasoning provide insight into the structure of arithmeticproofs obfuscated by the inference rule formulation of induction. For example, questionsconcerning the elimination of cut, consistency, and proof shape are given more clarity. Thesame could be said for functional interpretations of arithmetic such as system T whichenumerates the recursive functions provably total by arithmetic. A key feature of thesevariations on the formalization of arithmetic is that they get somewhat closer to formalizingthe concept of induction directly using the inferences of the LK-calculus, albeit byadding extra machinery at the meta-level. In this work we present a recursive sequentcalculus for arithmetic which can be syntactically translated into Gentzen formalism ofarithmetic and allows proof normalization to the LK-calculus with equality.},

year = {2018},

month = {January },

note = {In revision},

institution = {RISC},

length = {20}

}

### Mechanical Synthesis of Sorting Algorithms for Binary Trees by Logic and Combinatorial Techniques

#### Isabela Dramnesc, Tudor Jebelean, Sorin Stratulat

Journal of Symbolic Computation 90, pp. 3-41. 2018. Elsevier, 07477171. [url]**article**{RISC5715,

author = {Isabela Dramnesc and Tudor Jebelean and Sorin Stratulat},

title = {{Mechanical Synthesis of Sorting Algorithms for Binary Trees by Logic and Combinatorial Techniques}},

language = {english},

journal = {Journal of Symbolic Computation},

volume = {90},

pages = {3--41},

publisher = {Elsevier},

isbn_issn = {07477171},

year = {2018},

refereed = {yes},

keywords = {algorithm synthesis ; automated reasoning ; natural--style proving},

length = {39},

url = {https://doi.org/10.1016/j.jsc.2018.04.002}

}

### Pattern-based calculi with finitary matching

#### Sandra Alves, Besik Dundua, Mário Florido, Temur Kutsia

Logic Journal of the IGPL 26(2), pp. 203-243. 2018. ISSN 1367-0751. [url]**article**{RISC5763,

author = {Sandra Alves and Besik Dundua and Mário Florido and Temur Kutsia},

title = {{Pattern-based calculi with finitary matching}},

language = {english},

journal = {Logic Journal of the IGPL},

volume = {26},

number = {2},

pages = {203--243},

isbn_issn = {ISSN 1367-0751},

year = {2018},

refereed = {yes},

length = {41},

url = {https://doi.org/10.1093/JIGPAL/jzx059}

}

### Experiments with Automatic Proofs in Elementary Analysis

#### T. Jebelean

Technical report no. 18-06 in RISC Report Series, Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz, Schloss Hagenberg, 4232 Hagenberg, Austria. April 2018. Work in progress. [pdf] [zip] [pdf]**techreport**{RISC5692,

author = {T. Jebelean},

title = {{Experiments with Automatic Proofs in Elementary Analysis}},

language = {english},

abstract = {Combining methods from satisfiability checking with methods from symbolic computation promises to solve challenging problems in various areas of theory and application. We look at the basically equivalent problem of proving statements directly in a non--clausal setting, when additional information on the underlying domain is available in form of specific properties and algorithms.We demonstrate on some concrete examples several heuristic techniques for the automation of natural--style proving of statements from elementary analysis. The purpose of this work in progress is to generate proofs similar to those produced by humans, by combining automated reasoning methods with techniques from computer algebra.Our techniques include: the S-decomposition method for formulae with alternating quantifiers, quantifier elimination by cylindrical algebraic decomposition, analysis of terms behavior in zero, bounding the bounds, rewriting of expressions involving absolute value, algebraic manipulations, and identification of equal terms under unknown functions.These techniques are being implemented in the {\em Theorema} system and are able to construct automatically natural--style proofs for numerous examples including: convergence of sequences, limits and continuity of functions, uniform continuity, and other.},

number = {18-06},

year = {2018},

month = {April},

keywords = {Satisfiability Checking, Natural-style Proofs, Symbolic Computation},

sponsor = {European project ``Satisfiability Checking and Symbolic Computation'' (H2020-FETOPN-2015-CSA 712689)},

length = {33},

type = {Work in progress},

type = {RISC Report Series},

institution = {Research Institute for Symbolic Computation (RISC), Johannes Kepler University Linz},

address = {Schloss Hagenberg, 4232 Hagenberg, Austria}

}

### Idempotent Generalization is Infinitary

#### David M. Cerna and Temur Kutsia

RISC. Technical report, RISC Report, 2018. [pdf]**techreport**{RISC5529,

author = {David M. Cerna and Temur Kutsia},

title = {{Idempotent Generalization is Infinitary}},

language = {english},

abstract = {Let §\mathbf{I}_{S}$ be an equational theory s.t. for each $f\in S$, $f(x,x)=x$. Such an equational theory is said to be {\em idempotent}. It is known that the anti-unification problem (AUP) $f(a,b) \triangleq g(a,b)$ modulo $\mathbf{I}_{\lbrace f,g \rbrace}$ admits infinitely many least-general generalizers (lggs)~\cite{LPottier1989}. We show that, modulo $\mathbf{I}_{\lbrace f\rbrace}$, $f(a,f(a,b)) \triangleq f(b,f(a,b))$ admits infinitely many lggs.},

year = {2018},

howpublished = {RISC Report},

institution = {RISC},

length = {1}

}

### Gröbner Bases of Modules and Faugère's F4 Algorithm in Isabelle/HOL

#### A. Maletzky, F. Immler

In: Intelligent Computer Mathematics (Proceedings of CICM 2018, Hagenberg, Austria, August 13-17), Florian Rabe and William Farmer and Grant Passmore and Abdou Youssef (ed.), Proceedings of CICM 2018, Lecture Notes in Computer Science 11006, pp. 178-193. 2018. Springer, ISBN 978-3-319-96811-7. The final publication is available at Springer via https://doi.org/10.1007/978-3-319-96812-4_16. [url]**inproceedings**{RISC5733,

author = {A. Maletzky and F. Immler},

title = {{Gröbner Bases of Modules and Faugère's F4 Algorithm in Isabelle/HOL}},

booktitle = {{Intelligent Computer Mathematics (Proceedings of CICM 2018, Hagenberg, Austria, August 13-17)}},

language = {english},

series = {Lecture Notes in Computer Science},

volume = {11006},

pages = {178--193},

publisher = {Springer},

isbn_issn = {ISBN 978-3-319-96811-7},

year = {2018},

note = {The final publication is available at Springer via https://doi.org/10.1007/978-3-319-96812-4_16},

editor = {Florian Rabe and William Farmer and Grant Passmore and Abdou Youssef},

refereed = {yes},

length = {16},

conferencename = {CICM 2018},

url = {https://doi.org/10.1007/978-3-319-96812-4_16}

}

### Gröbner Bases of Modules and Faugère's F4 Algorithm in Isabelle/HOL (extended version)

#### A. Maletzky, F. Immler

RISC, JKU Linz. Technical report, May 2018. arXiv:1805.00304 [cs.LO]. [url]**techreport**{RISC5734,

author = {A. Maletzky and F. Immler},

title = {{Gröbner Bases of Modules and Faugère's F4 Algorithm in Isabelle/HOL (extended version)}},

language = {english},

year = {2018},

month = {May},

note = {arXiv:1805.00304 [cs.LO]},

institution = {RISC, JKU Linz},

length = {28},

url = {https://arxiv.org/abs/1805.00304}

}

### Gröbner Bases and Macaulay Matrices in Isabelle/HOL

#### A. Maletzky

RISC. Technical report, December 2018. [pdf]**techreport**{RISC5814,

author = {A. Maletzky},

title = {{Gröbner Bases and Macaulay Matrices in Isabelle/HOL}},

language = {english},

year = {2018},

month = {December},

institution = {RISC},

length = {15}

}

### A Generic and Executable Formalization of Signature-Based Gröbner Basis Algorithms

#### A. Maletzky

RISC. Technical report, September 2018. Submitted. [pdf]**techreport**{RISC5815,

author = {A. Maletzky},

title = {{A Generic and Executable Formalization of Signature-Based Gröbner Basis Algorithms}},

language = {english},

year = {2018},

month = {September},

note = {Submitted},

institution = {RISC},

length = {31}

}