- Full name:
- Alexandra Silva
- Formal name:
- Dr. A.M. Silva
- Function(s):
- Scientific Staff Member at Radboud Universiteit
- Telephone:
- +31(0)20 592 4053
- Room:
- L216
- Research groups:
- Formal Methods

### Research

During the last years my research has focused on aspects of theoretical computer science and the impact that logic and formal languages can have in the specification of behaviors of systems. The simplest specification language, invented in the 50's, in the context of the design of the most basic components of a computer -- digital circuits -- and still widely used today is that of regular expressions. It was invented by S.C. Kleene who also proved what is considered one of the cornerstones of computer science (and referred to as Kleene's theorem): the coincidence between the expressivity of regular expressions and finite deterministic automata.

The highlight of my dissertation is the generalization of this classical result, Kleene's theorem, to a wide variety of systems. The key observation for this generalization is the coalgebraic view on systems. The theory of coalgebras has emerged as a unified framework for describing behavior of dynamical systems, yielding instantiated results for a large variety of systems out of a single generic result. Using the framework presented in my dissertation one can derive specification languages and accompanying axiomatizations (which allow algebraic reasoning of equivalence of specifications) for many interesting dynamical systems, such as Mealy, weighted and probabilistic automata.

Apart from the material contained in my thesis, I have done other research. Together with J. Rutten, I studied the application of coalgebraic techniques to infinite data structures. In particular, we developed a coinductive calculus of binary trees. Together with D. Clarke and M. Bonsangue, I worked on a new semantic model for the coordination language Reo, which has allowed to correctly capture context dependent behavior that certain connectors exhibit. Together with C. Krause and Y.J. Moon, we extended the model with stochastic values, in order to be able to capture non functional aspects of a system such as delays, resource needs and consumption. In collaboration with M. Boreale, F. Bonchi, M. Bonsangue and J, Rutten, we are working on presenting several results on weighted automata in a uniform manner. With F. Bonchi, B. Koenig and M. H\"ulsbusch, we are developing a theory of weighted bisimulations, a notion of equivalence that will allow to measure how distant two systems are if one distinguishes between internal changes and changes induced by the environment. Recently, S. Milius extended the framework of my thesis to derive a specification language for closed stream circuits. Together with him and M. Bonsangue we are now investigating the possibility of handling open stream circuits. With F. Bonchi, M. Bonsangue and J. Rutten, we have generalized the classical powerset construction which allows to turn a non-deterministic automata into a deterministic one to a wide range of systems, among which weighted and probabilistic automata. I closely collaborate with G. Rosu and D. Lucanu, the developers of the coinductive theorem prover Circ. A large part of the results in my thesis have been incorporated in Circ.

### Career

2011 - 2016 | Facility Employee - Formal Methods |

2011 - 2012 | Facility Employee - Foundations of Software Engineering |

2010 - 2011 | Researcher - Foundations of Software Engineering |

2006 - 2010 | PhD Student - Foundations of Software Engineering |

### Selected Awards and Honours

2003 | Prémio de mérito escolar |

2004 | Prémio de mérito escolar |

2005 | MVS award - Most Valuable Student, Microsoft. |

2005 | Prémio de mérito escolar |

2006 | Bolsa de Estudo por Mérito a estudantes do Ensino Superior |

2006 | Prémio Caixa Geral de Depósitos |

2006 | Prémio de mérito escolar |

2007 | Prémio Engenheiro António de Almeida |

2007 | Prémio Governo Civil de Braga |

2007 | Prémio Senado Universitário |

2010 | Best presentation award |

2010 | Cum Laude (PhD thesis) |

### Selected Academic Activities

2007 | Organizer Workshop on Coinduction, Interaction and Composition |

2008 | Lecturer Universiteit Leiden - [UL] |

2008 - | Reviewer International Workshop on Coalgebraic Methods in Computer Science - [CMCS] |

2008 - | Reviewer International Workshop on Domain Specific Language - [DSL] |

2008 - | Reviewer International Workshop on Parallel and Distributed Methods in Verification - [PDMC] |

2009 | Lecturer Universiteit Leiden - [UL] |

2009 | Reviewer ACM SIGMOD International Conference on Management of Data - [SIGMOD] |

2009 | Reviewer Conference on the Mathematical Foundations of Programming Semantics - [MFPS] |

2009 | Reviewer IPM International Symposium on Fundamentals of Software Engineering - [FSEN] |

2009 | Reviewer International Conference on Foundations of Informatics, Computing and Software - [FICS] |

2009 | Reviewer International Conference on Rewriting Techniques and Applications - [RTA] |

2010 | Co-organizer Amsterdam, The Netherlands - Interaction and Concurrency Experience Workshop - [ICE] |

2010 | Co-organizer International Federated Conferences on Distributed Computing Techniques - [DisCoTec] |

2010 | Co-organizer Paphos, Cyprus - International Workshop on Coalgebraic Methods in Computer Science - [CMCS] |

2010 | Reviewer IEEE Symposium on Logic in Computer Science - [LICS] |

2010 | Reviewer International Conference on Concurrency Theory - [CONCUR] |

2010 | Reviewer International Conference on Concurrent Enterprising - [ICE] |

2010 | Reviewer International Workshop on Coalgebraic Methods in Computer Science - [CMCS] |

2010 | Reviewer International Workshop on Formal Aspects of Component Software - [FACS] |

2011 | Chair program committee Interaction and Concurrency Experience Workshop - [ICE] |

2011 | Reviewer IPM International Symposium on Fundamentals of Software Engineering - [FSEN] |

2011 | Reviewer SIGPLAN-SIGACT Symposium on Principles of Programming Languages - [POPL] |

Member of program committee International Conference on Concurrent Enterprising - [ICE] | |

Member of program committee International Conference on Quantitative Evaluation of SysTems - [QEST] - QEST 2011 | |

Member of program committee International Workshop on Coalgebraic Methods in Computer Science - [CMCS] | |

Member organizing committee Amsterdam, The Netherlands - International Federated Conferences on Distributed Computing Techniques - [DisCoTec] | |

Member organizing committee International Conference on Concurrent Enterprising - [ICE] | |

Member organizing committee International Conference on Concurrent Enterprising - [ICE] |

### Selected Publications

A. Silva, F. Bonchi, M.M. Bonsangue, J.J.M.M. Rutten. Generalizing the powerset construction, coalgebraically. Proceedings of IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science, Chennai, India, 272–283, 2010. |

M.M. Bonsangue, D. Clarke, A. Silva. A Model of Context-Dependent Component Connectors. Science of Computer Programming, 2010. |

M.M. Bonsangue, G. Caltais, E. Goriac, D. Lucanu, J.J.M.M. Rutten, A. Silva. A Decision Procedure for Bisimilarity of Generalized Regular Expressions. Proceedings of 13th Brazilian Symposium on Formal Methods, Natal, Brazil, 2010. |

A. Silva, F. Bonchi, M.M. Bonsangue, J.J.M.M. Rutten. Quantitative Kleene coalgebras. Information and Computation 209, 822–849, 2010. |

A. Silva, M.M. Bonsangue, J.J.M.M. Rutten. Non-deterministic Kleene coalgebras. Logical Methods in Computer Science, 2010. |

A. Silva. Kleene coalgebra. PhD thesis 2010. |

A. Silva, J.J.M.M. Rutten. A coinductive calculus of binary trees. Information and Computation 208, 578–593, 2010. |

F. Bonchi, M.M. Bonsangue, J.J.M.M. Rutten, A. Silva. Deriving Syntax and Axioms for Quantitative Regular Behaviours. Proceedings of International Conference on Concurrency Theory 2009 (20), Lecture Notes in Computer Science 5710, Bologna, Italy, 146–162, 2009. |

M.M. Bonsangue, D. Clarke, A. Silva. Automata for Context-Dependent Connectors. Proceedings of International Conference on Coordination Models and Languages 2009, 184–203, 2009. |

M.M. Bonsangue, J.J.M.M. Rutten, A. Silva. Algebras for Kripke polynomial coalgebras. Proceedings of Conference on Foundations of Software Science and Computation Structures 2009, 49–58, 2009. |

M.M. Bonsangue, J.J.M.M. Rutten, A. Silva. A Kleene theorem for polynomial coalgebras. Proceedings of Conference on Foundations of Software Science and Computation Structures 2009, Lecture Notes in Computer Science 5504, 122–136, 2009. |

M.M. Bonsangue, J.J.M.M. Rutten, A. Silva. Coalgebraic logic and synthesis of Mealy machines. , Lecture Notes in Computer Science 4962, Budapest, Hungary, 231–245, 2008. |

L.S. Barbosa, J.N. Oliveira, A. Silva. Calculating Invariants as Coreflexive Bisimulations. 2008. |

A. Silva, J.J.M.M. Rutten. Behavioural differential equations and coinduction for binary trees. Proceedings of WoLLIC 2007, Lecture Notes in Computer Science 4576, 322–336, 2007. |

A. Silva, J.M.W. Visser. Strong types for relational databases. Proceedings of ACM SIGPLAN Workshop on Haskell 2006, Portland, OR, USA, 25–36, 2006. |