Stijn Mostinckx

A survey on reactive programming

Reactive programming has recently gained popularity as a paradigm that is well-suited for developing event-driven and interactive applications. It facilitates the development of such applications by providing abstractions to express time-varying values and automatically managing dependencies between such values. A number of approaches have been recently proposed embedded in various languages such as Haskell, Scheme, JavaScript, Java, .NET, etc. This survey describes and provides a taxonomy of existing reactive programming approaches along six axes: representation of time-varying values, evaluation model, lifting operations, multidirectionality, glitch avoidance, and support for distribution. From this taxonomy, we observe that there are still open challenges in the field of reactive programming. For instance, multidirectionality is supported only by a small number of languages, which do not automatically track dependencies between time-varying values. Similarly, glitch avoidance, which is subtle in reactive programs, cannot be ensured in distributed reactive programs using the current techniques.

Ambient-Oriented programming in ambienttalk

A new field in distributed computing, called Ambient Intelligence, has emerged as a consequence of the increasing availability of wireless devices and the mobile networks they induce. Developing software for mobile networks is extremely hard in conventional programming languages because the network is dynamically demarcated. This leads us to postulate a suite of characteristics of future Ambient-Oriented Programming languages. A simple reflective programming language, called AmbientTalk, that meets the characteristics is presented. It is validated by implementing a collection of high level language features that are used in the implementation of an ambient messenger application.

Ambient-oriented programming in ambientTalk

A new field in distributed computing, called Ambient Intelligence, has emerged as a consequence of the increasing availability of wireless devices and the mobile networks they induce. Developing software for such mobile networks is extremely hard in conventional programming languages because of new distribution issues related to volatile network connections, dynamic network topologies and partial failures.

Ambient-oriented programming

A new field in distributed computing, called Ambient In-telligence, has emerged as a consequence of the increasing availability of wireless devices and the mobile networks they induce. Developing software for such mobile networks is extremely hard in conventional programming languages because the network is dynamically defined. This hardware phenomenon leads us to postulate a suite of characteristics of future Ambient-Oriented Programming languages. A simple re ective programming language kernel, called AmbientTalk, that meets these characteristics is subsequently presented. The power of the re ective kernel is illustrated by using it to conceive a collection of high level tentative ambient-oriented programming language features.

Fact spaces: coordination in the face of disconnection

Coordination languages for ad hoc networks with a fluid topology do not offer adequate support to detect and deal with device disconnection. Such a disconnection is particularly relevant if the device provided context information rather than emitting messages, as such context information then becomes invalid. This paper proposes the Fact Space Model which establishes a logic coordination language on top of LIMEs federated tuple space. In the model, the federated space offers applications a consistent view of their environment over which they can reason using logic rules. These rules encode which conclusions may be drawn from the presence of particular facts, and are similarly used to ensure the consistency of these conclusions when devices go out of range. By allowing applications to add application-specific hooks to these rules, the application programmer is offered a general-purpose mechanism to respond to the discovery and disconnection of devices.

Linguistic symbiosis between event loop actors and threads

In modern programming languages, concurrency control can be traced back to one of two different schools: actor-based message passing concurrency and thread-based shared-state concurrency. This paper describes a linguistic symbiosis between two programming languages with such different concurrency models. More specifically, we describe a novel symbiosis between actors represented as event loops on the one hand and threads on the other. This symbiosis ensures that the invariants of the actor-based concurrency model are not violated by engaging in symbiosis with multithreaded programs. The proposed mapping is validated by means of a concrete symbiosis between AmbientTalk, a flexible, domain-specific language for writing distributed programs and Java, a conventional object-oriented language. This symbiosis allows the domain-specific language to reuse existing software components written in a multithreaded language without sacrificing the beneficial event-driven properties of the actor concurrency model.

Loosely-coupled distributed reactive programming in mobile ad hoc networks

Pervasive applications running on mobile ad hoc networks have to be conceived as loosely-coupled event-driven architectures because of the dynamic nature of both the underlying network and the applications running on top of them. Such architectures can become tedious to develop and understand when the number of events and event handlers increases. The reason is that the control flow of the application is driven by event handlers or callbacks which are triggered independently and are scattered throughout the application code. In this paper, we propose a number of language constructs that reconcile the elegant processing of events of a reactive programming system with the loose coupling of a publish/subscribe system that is required to cope with the dynamic nature of mobile ad hoc networks.

Mirages: behavioral intercession in a mirror-based architecture

Mirror-based systems are object-oriented reflective architectures built around a set of design principles that lead to reflective APIs which foster a high degree of reusability, loose coupling with base-level objects and whose structure and design corresponds to the system being mirrored. However, support for behavioral intercession has been limited in contemporary mirror-based architectures, in spite of its many interesting applications. This is due to the fact that mirror-based architectures only support explicit reflection, while behavioral intercession requires implicit reflection. This work reconciles mirrors with behavioral intercession. We discuss the design of a mirror-based architecture with implicit mirrors that can be absorbed in the interpreter, and mirages, base objects whose semantics are defined by implicit mirrors. We describe and illustrate the integration of this reflective architecture for the distributed object-oriented programming language AmbientTalk.

Ambient references: addressing objects in mobile networks

A significant body of research in ubiquitous computing deals with mobile networks, i.e. networks of mobile devices interconnected by wireless communication links. Due to the very nature of such mobile networks, addressing and communicating with remote objects is significantly more difficult than in their fixed counterparts. This paper reconsiders the remote object reference concept - one of the most fundamental programming ions of distributed programming languages - in the context of mobile networks. We describe four desirable characteristics of remote References in mobile networks, show how existing remote object References fail to exhibit them, and subsequently propose ambient references: remote object references designed for mobile networks.

The context-dependent role model

Implementing context-dependent behaviour of pervasive computing applications puts a great burden on programmers: Devices need to continuously adapt not only to their own context, but also to the context of other devices they interact with. We present an approach that modularises behavioural adaptations into roles. Role selection takes the context of all the devices involved in an interaction into account, ensures an unambiguous scope of adaptation even in the presence of concurrency, and protects the privacy of the devices. Thus, our context-dependent role (CDR) model facilitates expressing interactions between applications in different, possibly conflicting contexts.