Florian Funke
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View article: Building a Data Management System for the Cloud: Lessons Learned and Future Directions
Building a Data Management System for the Cloud: Lessons Learned and Future Directions Open
The paper discusses the lessons learned from building Snowflake, a data management system for the cloud. Given the need for systems that can scale to handle large data volumes, provide expressive programming interfaces, and leverage the be…
View article: Probabilistic causes in Markov chains
Probabilistic causes in Markov chains Open
By combining two of the central paradigms of causality, namely counterfactual reasoning and probability-raising , we introduce a probabilistic notion of cause in Markov chains. Such a cause consists of finite executions of the probabilisti…
View article: On probability-raising causality in Markov decision processes
On probability-raising causality in Markov decision processes Open
The purpose of this paper is to introduce a notion of causality in Markov decision processes based on the probability-raising principle and to analyze its algorithmic properties. The latter includes algorithms for checking cause-effect rel…
View article: On probability-raising causality in Markov decision processes
On probability-raising causality in Markov decision processes Open
The purpose of this paper is to introduce a notion of causality in Markov decision processes based on the probability-raising principle and to analyze its algorithmic properties. The latter includes algorithms for checking cause-effect rel…
View article: Parameter Synthesis for Parametric Probabilistic Dynamical Systems and Prefix-Independent Specifications
Parameter Synthesis for Parametric Probabilistic Dynamical Systems and Prefix-Independent Specifications Open
We consider the model-checking problem for parametric probabilistic dynamical systems, formalised as Markov chains with parametric transition functions, analysed under the distribution-transformer semantics (in which a Markov chain induces…
View article: A Game-Theoretic Account of Responsibility Allocation
A Game-Theoretic Account of Responsibility Allocation Open
When designing or analyzing multi-agent systems, a fundamental problem is responsibility ascription: to specify which agents are responsible for the joint outcome of their behaviors and to which extent. We model strategic multi-agent inter…
View article: Responsibility and verification: Importance value in temporal logics
Responsibility and verification: Importance value in temporal logics Open
We aim at measuring the influence of the nondeterministic choices of a part of a system on its ability to satisfy a specification. For this purpose, we apply the concept of Shapley values to verification as a means to evaluate how importan…
View article: From Verification to Causality-based Explications
From Verification to Causality-based Explications Open
In view of the growing complexity of modern software architectures, formal models are increasingly used to understand why a system works the way it does, opposed to simply verifying that it behaves as intended. This paper surveys approache…
View article: Responsibility Attribution in Parameterized Markovian Models
Responsibility Attribution in Parameterized Markovian Models Open
We consider the problem of responsibility attribution in the setting of parametric Markov chains. Given a family of Markov chains over a set of parameters, and a property, responsibility attribution asks how the difference in the value of …
View article: Probabilistic causes in Markov chains
Probabilistic causes in Markov chains Open
The paper studies a probabilistic notion of causes in Markov chains that relies on the counterfactuality principle and the probability-raising property. This notion is motivated by the use of causes for monitoring purposes where the aim is…
View article: From Verification to Causality-Based Explications (Invited Talk)
From Verification to Causality-Based Explications (Invited Talk) Open
In view of the growing complexity of modern software architectures, formal models are increasingly used to understand why a system works the way it does, opposed to simply verifying that it behaves as intended. This paper surveys approache…
View article: The Orbit Problem for Parametric Linear Dynamical Systems
The Orbit Problem for Parametric Linear Dynamical Systems Open
We study a parametric version of the Kannan-Lipton Orbit Problem for linear dynamical systems. We show decidability in the case of one parameter and Skolem-hardness with two or more parameters. More precisely, consider a d-dimensional squa…
View article: Reachability in Dynamical Systems with Rounding
Reachability in Dynamical Systems with Rounding Open
We consider reachability in dynamical systems with discrete linear updates, but with fixed digital precision, i.e., such that values of the system are rounded at each step. Given a matrix $M \in \mathbb{Q}^{d \times d}$, an initial vector …
View article: SWITSS: Computing Small Witnessing Subsystems
SWITSS: Computing Small Witnessing Subsystems Open
Witnessing subsystems for probabilistic reachability thresholds in discrete Markovian models are an important concept both as diagnostic information on why a property holds, and as input to refinement algorithms. We present SWITSS, a tool …
View article: Reachability in Dynamical Systems with Rounding
Reachability in Dynamical Systems with Rounding Open
We consider reachability in dynamical systems with discrete linear updates, but with fixed digital precision, i.e., such that values of the system are rounded at each step. Given a matrix M ∈ ℚ^{d × d}, an initial vector x ∈ ℚ^{d}, a granu…
View article: fmcad20-material.zip
fmcad20-material.zip Open
Supplementary material to the FMCAD'20 paper "SWITSS: Computing Small Witnessing Subsystems"
View article: fmcad20-material.zip
fmcad20-material.zip Open
Supplementary material to the FMCAD'20 paper "SWITSS: Computing Small Witnessing Subsystems"
View article: SWITSS: Computing Small Witnessing Subsystems
SWITSS: Computing Small Witnessing Subsystems Open
Witnessing subsystems for probabilistic reachability thresholds in discrete Markovian models are an important concept both as diagnostic information on why a property holds, and as input to refinement algorithms. We present Switss, a tool …
View article: On the Complexity of Multi-Pushdown Games
On the Complexity of Multi-Pushdown Games Open
We study the influence of parameters like the number of contexts, phases, and stacks on the complexity of solving parity games over concurrent recursive programs. Our first result shows that k-context games are b-EXPTIME-complete, where b …
View article: Farkas certificates and minimal witnesses for probabilistic reachability constraints
Farkas certificates and minimal witnesses for probabilistic reachability constraints Open
This paper introduces Farkas certificates for lower and upper bounds on minimal and maximal reachability probabilities in Markov decision processes (MDP), which we derive using an MDP-variant of Farkas' Lemma. The set of all such certifica…
View article: The integral polytope group
The integral polytope group Open
We show that the Grothendieck group associated to integral polytopes in ℝ n is free-abelian, by providing an explicit basis. Moreover, we identify the involution on this polytope group given by reflection about the origin as a sum of Euler…
View article: The $L^2$-Torsion Polytope of Amenable Groups
The $L^2$-Torsion Polytope of Amenable Groups Open
We introduce the notion of groups of polytope class and show that torsion-free amenable groups satisfying the Atiyah Conjecture possess this property. A direct consequence is the homotopy invariance of the $L^2$-torsion polytope among $G$-…
View article: The $L^2$-Torsion Polytope of Amenable Groups
The $L^2$-Torsion Polytope of Amenable Groups Open
We introduce the notion of groups of polytope class and show that torsion-free amenable groups satisfying the Atiyah Conjecture possess this property. A direct consequence is the homotopy invariance of the L^2 -torsion polytope among G -CW…
View article: The $L^2$-torsion polytope of amenable groups
The $L^2$-torsion polytope of amenable groups Open
We introduce the notion of groups of polytope class and show that torsion-free amenable groups satisfying the Atiyah Conjecture possess this property. A direct consequence is the homotopy invariance of the $L^2$-torsion polytope among $G$-…
View article: The Grothendieck group of polytopes and norms
The Grothendieck group of polytopes and norms Open
Polytopes in R with integral vertices form a monoid under the Minkowski sum, and the Grothendieck construction gives rise to a group. We show that every symmetric polytope is a norm in this group for every n.
View article: Data Blocks
Data Blocks Open
This work aims at reducing the main-memory footprint in high performance hybrid OLTP & OLAP databases, while retaining high query performance and transactional throughput. For this purpose, an innovative compressed columnar
\nstorage forma…