@misc{5395, abstract = {We study observation-based strategies for partially-observable Markov decision processes (POMDPs) with omega-regular objectives. An observation-based strategy relies on partial information about the history of a play, namely, on the past sequence of observa- tions. We consider the qualitative analysis problem: given a POMDP with an omega-regular objective, whether there is an observation-based strategy to achieve the objective with probability 1 (almost-sure winning), or with positive probability (positive winning). Our main results are twofold. First, we present a complete picture of the computational complexity of the qualitative analysis of POMDPs with parity objectives (a canonical form to express omega-regular objectives) and its subclasses. Our contribution consists in establishing several upper and lower bounds that were not known in literature. Second, we present optimal bounds (matching upper and lower bounds) on the memory required by pure and randomized observation-based strategies for the qualitative analysis of POMDPs with parity objectives and its subclasses.}, author = {Chatterjee, Krishnendu and Doyen, Laurent and Henzinger, Thomas A}, issn = {2664-1690}, pages = {20}, publisher = {IST Austria}, title = {{Qualitative analysis of partially-observable Markov decision processes}}, doi = {10.15479/AT:IST-2009-0001}, year = {2009}, } @inproceedings{3837, abstract = {In this paper we extend the work of Alfaro, Henzinger et al. on interface theories for component-based design. Existing interface theories often fail to capture functional relations between the inputs and outputs of an interface. For example, a simple synchronous interface that takes as input a number n ≥ 0 and returns, at the same time, as output n + 1, cannot be expressed in existing theories. In this paper we provide a theory of relational interfaces, where such input-output relations can be captured. Our theory supports synchronous interfaces, both stateless and stateful. It includes explicit notions of environments and pluggability, and satisfies fundamental properties such as preservation of refinement by composition, and characterization of pluggability by refinement. We achieve these properties by making reasonable restrictions on feedback loops in interface compositions.}, author = {Tripakis, Stavros and Lickly, Ben and Henzinger, Thomas A and Lee, Edward}, booktitle = {EMSOFT '09 Proceedings of the seventh ACM international conference on Embedded software}, location = {Grenoble, France}, pages = {67 -- 76}, publisher = {ACM}, title = {{On relational interfaces}}, doi = {10.1145/1629335.1629346}, year = {2009}, } @inproceedings{3841, abstract = {We compare several languages for specifying Markovian population models such as queuing networks and chemical reaction networks. These languages —matrix descriptions, stochastic Petri nets, stoichiometric equations, stochastic process algebras, and guarded command models— all describe continuous-time Markov chains, but they differ according to important properties, such as compositionality, expressiveness and succinctness, executability, ease of use, and the support they provide for checking the well-formedness of a model and for analyzing a model. }, author = {Henzinger, Thomas A and Jobstmann, Barbara and Wolf, Verena}, location = {Palaiseau, France}, pages = {3 -- 23}, publisher = {Springer}, title = {{Formalisms for specifying Markovian population models}}, doi = {10.1007/978-3-642-04420-5_2}, volume = {5797}, year = {2009}, } @inproceedings{3843, abstract = {Within systems biology there is an increasing interest in the stochastic behavior of biochemical reaction networks. An appropriate stochastic description is provided by the chemical master equation, which represents a continuous- time Markov chain (CTMC). Standard Uniformization (SU) is an efficient method for the transient analysis of CTMCs. For systems with very different time scales, such as biochemical reaction networks, SU is computationally expensive. In these cases, a variant of SU, called adaptive uniformization (AU), is known to reduce the large number of iterations needed by SU. The additional difficulty of AU is that it requires the solution of a birth process. In this paper we present an on-the-fly variant of AU, where we improve the original algorithm for AU at the cost of a small approximation error. By means of several examples, we show that our approach is particularly well-suited for biochemical reaction networks.}, author = {Didier, Frédéric and Henzinger, Thomas A and Mateescu, Maria and Wolf, Verena}, location = {Trento, Italy}, number = {6}, pages = {118 -- 127}, publisher = {IEEE}, title = {{Fast adaptive uniformization of the chemical master equation}}, doi = {10.1109/HiBi.2009.23}, volume = {4}, year = {2009}, } @inproceedings{3844, abstract = {The Hierarchical Timing Language (HTL) is a real-time coordination language for distributed control systems. HTL programs must be checked for well-formedness, race freedom, transmission safety (schedulability of inter-host communication), and time safety (schedulability of host computation). We present a modular abstract syntax and semantics for HTL, modular checks of well-formedness, race freedom, and transmission safety, and modular code distribution. Our contributions here complement previous results on HTL time safety and modular code generation. Modularity in HTL can be utilized in easy program composition as well as fast program analysis and code generation, but also in so-called runtime patching, where program components may be modified at runtime.}, author = {Henzinger, Thomas A and Kirsch, Christoph and Marques, Eduardo and Sokolova, Ana}, location = {Washington, DC, United States}, pages = {171 -- 180}, publisher = {IEEE}, title = {{Distributed, modular HTL}}, doi = {10.1109/RTSS.2009.9}, year = {2009}, }