Guillaume Baudart

A synchronous embedding of Antescofo, a domain-specific language for interactive mixed music

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.

Programming mixed music in ReactiveML

Mixed music is about live musicians interacting with electronic parts which are controlled by a computer during the performance. It allows composers to use and combine traditional instruments with complex synthesized sounds and other electronic devices. There are several languages dedicated to the writing of mixed music scores. Among them, the Antescofo language coupled with an advanced score follower allows a composer to manage the reactive aspects of musical performances: how electronic parts interact with a musician. However these domain specific languages do not offer the expressiveness of functional programming. We embed the Antescofo language in a reactive functional programming language, ReactiveML. This approach offers to the composer recursion, higher order, inductive types, as well as a simple way to program complex reactive behaviors thanks to the synchronous model of concurrency on which ReactiveML is built. This article presents how to program mixed music in ReactiveML through several examples.

Protecting chatbots from toxic content

There is a paradigm shift in web-based services towards conversational user interfaces. Companies increasingly offer conversational interfaces, or chatbots, to let their customers or employees interact with their services in a more flexible and mobile manner. Unfortunately, this new paradigm faces a major problem, namely toxic content in user inputs. Toxic content in user inputs to chatbots may cause privacy concerns, may be adversarial or malicious, and can cause the chatbot provider substantial economic, reputational, or legal harm. We address this problem with an interdisciplinary approach, drawing upon programming languages, cloud computing, and other disciplines to build protections for chatbots. Our solution, called BotShield, is non-intrusive in that it does not require changes to existing chatbots or underlying conversational platforms. This paper introduces novel security mechanisms, articulates their security guarantees, and illustrates them via case studies.

A reactive language for analyzing cloud logs

Log analysis is required in many domains, and especially in the emerging field of cloud computing. Cloud applications are often built by composing diverse services. When something goes wrong, finding the root cause of the problem can be difficult. Many services are only reachable through their Application Programming Interfaces (APIs) with no possibility for live introspection. In this context, logs become an essential tool for monitoring and debugging. Cloud services typically generate very large quantities of log messages, with formats that may not be well specified and may vary over time. In this paper, we present CloudLens, a language for the analysis of semi-structured textual data as found in logs, and specify its formal semantics. CloudLens is a reactive language and views logs as streams of objects. Our objective is to facilitate exploring the contents of logs interactively and to write reusable analyses succinctly, using familiar constructs. We implemented an interpreter for the Apache Zeppelin notebook to provide an interactive IDE. Our prototype implementation is open source and we report on a detailed case study using logs from the Apache OpenWhisk project.

Reactive chatbot programming

Chatbots are reactive applications with a conversational interface. They are usually implemented as compositions of client-side components and cloud-hosted services, including artificial-intelligence technology. Unfortunately, programming such reactive multi-tier applications with traditional programming languages is cumbersome. This paper introduces wcs-ocaml, a new multi-tier chatbot generator library designed for use with the reactive language ReactiveML. The paper explains our library with small didactic examples throughout, and closes with a larger case-study of a chatbot for authoring event-processing rules.

Soundness of the quasi-synchronous abstraction

Many critical real-time embedded systems are implemented as a set of processes that execute periodically with bounded jitter and communicate with bounded transmission delay. The quasi-synchronous abstraction was introduced by P. Caspi for model-checking the safety properties of applications running on such systems. The simplicity of the abstraction is appealing: the only events are process activations; logical steps account for transmission delays; and no process may be activated more than twice between two successive activations of any other. We formalize the relation between the real-time model and the quasi-synchronous abstraction by introducing the notion of a unitary discretization. Even though the abstraction has been applied several times in the literature, we show, surprisingly, that it is not sound for general systems of more than two processes. Our central result is to propose necessary and sufficient conditions on both communication topologies and timing parameters to recover soundness.