Carlos Olarte

A Declarative Language for Dynamic Multimedia Interaction Systems

Universal Timed Concurrent Constraint Programming (utcc) is a declarative model for concurrency tied to logic. It aims at specifying mobile reactive systems, i.e., systems that continuously interact with the environment and may change their communication structure. In this paper we argue for utcc as a declarative model for dynamic multimedia interaction systems. Firstly, we show that the notion of constraints as partial information allows us to neatly define temporal relations between interactive agents or events. Secondly, we show that mobility in utcc allows for the specification of more flexible and expressive systems. Thirdly, by relying on the underlying temporal logic in utcc, we show how non-trivial temporal properties of the model can be verified. We give two compelling applications of our approach. We propose a model for dynamic interactive scores where interactive points can be defined to adapt the hierarchical structure of the score depending on the information inferred from the environment. We then broaden the interaction mechanisms available for the composer in previous (more static) models. We also model a music improvisation system based on the factor oracle that scales up to situations involving several players, learners and improvisers.

Declarative diagnosis of temporal concurrent constraint programs

We present a framework for the declarative diagnosis of nondeterministic timed concurrent constraint programs. We present a denotational semantics based on a (continuous) immediate consequence operator, TD, which models the process behaviour associated with a program D given in terms of sequences of constraints. Then, we show that, given the intended specification of D, it is possible to check the correctness of D by a single step of TD. In order to develop an effective debugging method, we approximate the denotational semantics of D. We formalize this method by abstract interpretation techniques, and we derive a finitely terminating abstract diagnosis method, which can be used statically. We define an abstract domain which allows us to approximate the infinite sequences by a finite cut. As a further development we show how to use a specific linear temporal logic for deriving automatically the debugging sequences. Our debugging framework does not require the user to either provide error symptoms in advance or answer questions concerning program correctness. Our method is compositional, that may allow to master the complexity of the debugging methodology.

A framework for abstract interpretation of timed concurrent constraint programs

Timed Concurrent Constraint Programming (tcc) is a declarative model for concurrency offering a logic for specifying reactive systems, i.e. systems that continuously interact with the environment. The universal tcc formalism (utcc) is an extension of tcc with the ability to express mobility. Here mobility is understood as communication of private names as typically done for mobile systems and security protocols. In this paper we consider the denotational semantics for tcc, and we extend it to a collecting semantics for utcc based on closure operators over sequences of constraints. Relying on this semantics, we formalize the first general framework for data flow analyses of tcc and utcc programs by abstract interpretation techniques. The concrete and abstract semantics we propose are compositional, thus allowing us to reduce the complexity of data flow analyses. We show that our method is sound and parametric w.r.t. the abstract domain. Thus, different analyses can be performed by instantiating the framework. We illustrate how it is possible to reuse abstract domains previously defined for logic programming, e.g., to perform a groundness analysis for tcc programs. We show the applicability of this analysis in the context of reactive systems. Furthermore, we make also use of the abstract semantics to exhibit a secrecy flaw in a security protocol. We have developed a prototypical implementation of our methodology and we have implemented the abstract domain for security to perform automatically the secrecy analysis.

Universal timed concurrent constraint programming

In this doctoral work we aim at developing a rich timed concurrent constraint (tcc) based language with strong ties to logic. The new calculus called Universal Timed Concurrent Constraint (utcc) increases the expressiveness of tcc languages allowing infinite behaviour and mobility. We introduce a constructor of the form (abs x, c)P (Abstraction in P) that can be viewed as a dual operator of the hidden operator local x in P. i.e. the later can be viewed as an existential quantification on the variable x and the former as an universal quantification of x, executing P[t/x] for all t s.t. the current store entails c[t/x]. As a compelling application, we applied this calculus to verify security protocols.