Antescofo is recently developed software for musical score following and mixed music: it automatically, and in real-time, synchronizes electronic instruments with a musician playing on a classical instrument. Therefore, it faces some of the same major challenges as embedded systems. The system provides a programming language used by composers to specify musical pieces that mix interacting electronic and classical instruments. This language is developed with and for musicians and it continues to evolve according to their needs. Yet its semantics has only recently been formally defined. This paper presents a synchronous semantics for the core language of Antescofo and an alternative implementation based on an embedding inside an existing synchronous language, namely ReactiveML. The semantics reduces to a few rules, is mathematically precise and leads to an interpretor of only a few hundred lines. The efficiency of this interpretor compares well with that of the actual implementation: on all musical pieces we have tested, response times have been less than the reaction time of the human ear. Moreover, this embedding permitted the prototyping of several new programming constructs, some of which are described in this paper.

We define tree automata with global constraints (TAGC), generalizing the class of tree automata with global equality and disequality constraints (TAGED). TAGC can test for equality and disequality between subterms whose positions are defined by the states reached during a computation. In particular, TAGC can check that all the subterms reaching a given state are distinct. This constraint is related to monadic key constraints for XML documents, meaning that every two distinct positions of a given type have different values. We prove decidability of the emptiness problem for TAGC. This solves, in particular, the open question of decidability of emptiness for TAGED. We further extend our result by allowing global arithmetic constraints for counting the number of occurrences of some state or the number of different subterms reaching some state during a computation. We also allow local equality and disequality tests between sibling positions and the extension to unranked ordered trees. As a consequence of our results for TAGC, we prove the decidability of a fragment of the monadic second order logic on trees extended with predicates for equality and disequality between subtrees, and cardinality.

We propose a model for XML update primitives of the W3C XQuery Update Facility as parameterized rewriting rules of the form: "insert an unranked tree from a regular tree language L as the first child of a node labeled by a". For these rules, we give type inference algorithms, considering types defined by several classes of unranked tree automata. These type inference algorithms are directly applicable to XML static typechecking, which is the problem of verifying whether, a given document transformation always converts source documents of a given input type into documents of a given output type. We show that typechecking for arbitrary sequences of XML update primitives can be done in polynomial time when the unranked tree automaton defining the output type is deterministic and complete, and that it is EXPTIME-complete otherwise.

The configuration of firewalls is highly error prone and automated solution are needed in order to analyze its correctness. We propose a formal and automatic method for checking whether a firewall reacts correctly with respect to a security policy given in an high level declarative language. When errors are detected, some feedback is returned to the user in order to correct the firewall configuration. Furthermore, the procedure verifies that no conflicts exist within the security policy. We show that our method is both correct and complete. Finally, it has been implemented in a prototype of verifier based on a satisfiability solver modulo theories (SMT). Experiment conducted on relevant case studies demonstrate the efficiency and scalability of the approach.

Tree automata with one memory have been introduced in 2001. They generalize both pushdown (word) automata and the tree automata with constraints of equality between brothers of Bogaert and Tison. Though it has a decidable emptiness problem, the main weakness of this model is its lack of good closure properties. We propose a generalization of the visibly pushdown automata of Alur and Madhusudan to a family of tree recognizers which carry along their (bottom-up) computation an auxiliary unbounded memory with a tree structure (instead of a symbol stack). In other words, these recognizers, called Visibly Tree Automata with Memory (VTAM) define a subclass of tree automata with one memory enjoying Boolean closure properties. We show in particular that they can be determinized and the problems like emptiness, membership, inclusion and universality are decidable for VTAM. Moreover, we propose several extensions of VTAM whose transitions may be constrained by different kinds of tests between memories and also constraints a la Bogaert and Tison comparing brother subtrees in the tree in input. We show that some of these classes of constrained VTAM keep the good closure and decidability properties, and we demonstrate their expressiveness with relevant examples of tree languages.

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We prove that ground reducibility is EXPTIME-complete in the general case. EXPTIME-hardness is proved by encoding the computations of an alternating Turing machine whose space is polynomially bounded. It is more difficult to show that ground reducibility belongs to DEXPTIME. We associate first an automaton with disequality constraints A/sub R,t/ to a rewrite system R and a term t. This automaton is deterministic and accepts a term u if and only if t is not ground reducible by R. The number of states of A/sub R,t/ is O(2/sup /spl par/R/spl par//spl times//spl par/t/spl par//) and the size of the constraints are polynomial in the size of R,t. Then we prove some new pumping lemmas, using a total ordering on the computations of the automaton. Thanks to these lemmas, we can give an upper bound to the number of distinct subtrees of a minimal successful computation of an automaton with disequality constraints. It follows that emptiness of such an automaton can be decided in time polynomial in the number of its states and exponential in the size of its constraints. Altogether, we get a simply exponential deterministic algorithm for ground reducibility.