Section: New Results

Programming support for Autonomic Computing

Reactive languages

Participants : Gwenaël Delaval, Eric Rutten.

Our work in reactive programming for autonomic computing systems is focused on the specification and compilation of declarative control objectives, under the form of contracts, enforced upon classical mode automata as defined in synchronous languages. The compilation involves a phase of Discrete Controller Synthesis, integrating the tool ReaX, in order to obtain an imperative executable code. The programming language Heptagon / BZR (see Section Software and Platforms) integrates our research results [6].

Recent work concerns exploring new possibilities offered by logico-numeric control. We consider Symbolic Limited Lookahead Control for Best-effort Dynamic Computing Resource Management. We put forward a new modeling technique for Dynamic Resource Management (DRM) based on discrete events control for symbolic logico-numerical systems, especially Discrete Controller Synthesis (DCS). The resulting models involve state and input variables defined on an infinite domain (Integers), thereby no exact DCS algorithm exists for safety control. We thus formally define the notion of limited lookahead, and associated best-effort control objectives targeting safety and optimization on a sliding window for a number of steps ahead. We give symbolic algorithms, illustrate our approach on an example model for DRM, and report on performance results based on an implementation in the tool ReaX. This work is in cooperation with the Sumo team at Inria Rennes (Hervé Marchand) and University of Liverpool (Nicolas Berthier), and is published in the WODES 2018 conference [14].

We also have ongoing activities on abstraction methods for compilation using discrete controller synthesis (needed for example, in order to program the controllers for systems where the useful data for control can be of arbitrary types (integer, real, ...) , or also for systems which are naturally distributed, and require a decentralized controller) and on compilation and diagnosis for discrete controller synthesis (which is made special by the declarative nature of the compilation, where it is not easy to precisely diagnose cases where no solution can be found).

On the applicative side, we also consider such modular and logico-numeric approaches for the control of different targets in self-adaptive and reconfigurable systems (see below in Section 6.2.2.1 and 6.2.1.3 [20], [15].

Domain-specific languages

Participants : Gwenaël Delaval, Soguy Mak Kare Gueye, Eric Rutten.

Our work in Domain-specific languages (DSLs) is founded on our work in component-based programming for autonomic computing systems as examplified by e.g., Fractal . We consider essentially the problem of specifying the control of components assembly reconfiguration, with an approach based on the integration within such a component-based framework of a reactive language as in Section 6.1.1 [5].

In recent work, we proposed an extension of a classical Software Architecture Description Languages (ADL) with Ctrl-F, DSL for the specification of dynamic reconfiguration behavior in a [1].

Based on this experience, we are working on a proposal for a DSL called Ctrl-DPR, allowing designers to easily generate Autonomic Managers for DPR FPGA systems (see Section 6.2.1.3). Users can describe their system and their management strategies, in terms of the entities composing the system : tasks, versions, applications, ressources, policies. The DSL relies on a behavioral modeling of these entities, targeted at the design of autonomic managers to control the reconfigurations in such a way as to enforce given policies and strategies. These model-based control techniques are embedded in a compiler, connected to the reactive language and discrete controller synthesis tool of Section 6.1.1, which enables to generate a C implementation of the controller enforcing the management strategies. We apply our DSL for the management of a video application on a UAV. This work is in cooperation with LabSticc in Lorient (Jean-Philippe Diguet), and is published in the ICAC 2018 conference [16].

Ongoing work involves a generalization from our experiences in software components, DPR FPGA, as well as Rule-based autonomic manager as in Section 6.1.3. As we observed a similarity in objects and structures (e.g., tasks, implmentation versions, resources, and upper-level application layer), we are considering a more general DSL, which could be specialized towards such different target domains, and where the compilation towards reactive models could be studied and improved, especially considering the features of Section 6.1.1. This direction will also lead us to study the definition of architectural patterns for multiple loop Autonomic Managers, particularly hierarchical, with lower layers autonomy alleviating management burden from the upper layers.

Rule-based systems

Participants : Adja Sylla, Gwenaël Delaval, Eric Rutten.

This work concerns a high-level language for safe rule-based programming in the LINC transactional rule-based platform developed at CEA [10]. Rule based middlewares such as LINC enable high level programming of distributed adaptive systems behaviours. LINC also provides the systems with transactional guarantees and hence ensures their reliability at runtime. However, the set of rules may contain design errors (e.g. conflicts, violations of constraints) that can bring the system in unsafe safe or undesirables states, despite the guarantees provided by LINC. On the other hand, automata based languages such as Heptagon/BZR enable formal verification and especially synthesis of discrete controllers to deal with design errors. Our work studies these two languages and combines their execution mechanisms, from a technical perspective. We target applications to the domain of Internet of Things and more particularly smart building, office or home (see Section 6.2.2.1).

This work is in cooperation with CEA LETI/DACLE (Maxime Louvel), it was the topic of the PhD of Adja Sylla at CEA, co-advised with M. Louvel, and aspects on applications of logico-numeric control are published in the CCTA 2018 conference [20].