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Ecological, environmental and geophysical time series consistently exhibit the characteristics of coloured (1/ƒβ) noise. Here we briefly survey the literature on coloured noise, population persistence and related evolutionary dynamics, before introducing coloured noise as an appropriate model for environmental variation in artificial evolutionary systems. To illustrate and explore the effects of different noise colours, a simple evolutionary model that examines the trade-off between specialism and generalism in fluctuating environments is applied. The results of the model clearly demonstrate a need for greater generalism as environmental variability becomes ‘whiter’, whilst specialisation is favoured as environmental variability becomes ‘redder’. Pink noise, sitting midway between white and red noise, is shown to be the point at which the pressures for generalism and specialism balance, providing some insight in to why ‘pinker’ noise is increasingly being seen as an appropriate model of typical environmental variability. We go on to discuss how the results presented here feed in to a wider discussion on evolutionary responses to fluctuating environments. Ultimately we argue that Artificial Life as a field should embrace the use of coloured noise to produce models of environmental variability.

Change-based persistence has the potential to support faster and more accurate model comparison, merging, as well as a range of analytics activities. However, reconstructing the state of a model by replaying its editing history every time the model needs to be queried or modified can get increasingly expensive as the model grows in size. In this work, we integrate change-based and state-based persistence mechanisms in a hybrid model persistence approach that delivers the best of both worlds. In this paper, we present the design of our hybrid model persistence approach and report on its impact on time and memory footprint for model loading, saving, and storage space usage.

Local search based meta-heuristics such as variable neighbourhood search have achieved remarkable success in solving complex combinatorial problems. Local search techniques are becoming increasingly popular and are used in a wide variety of meta-heuristics, such as genetic algorithms. Typically, local search iteratively improves a solution by making a series of small moves. Traditionally these methods do not employ any learning mechanism. We treat the selection of a local search neighbourhood as a dynamic multi- armed bandit (D-MAB) problem where learning techniques for solving the D-MAB can be used to guide the local search process. We present a D-MAB neighbourhood search (D-MABNS) which can be embedded within any meta- heuristic or hyperheuristic framework. Given a set of neighbourhoods, the aim of D-MABNS is to adapt the search sequence, testing promising solutions rst. We demonstrate the eectiveness of D-MABNS on two vehicle routing and scheduling problems, the real-world geographically distributed mainte- nance problem (GDMP) and the periodic vehicle routing problem (PVRP). We present comparisons to benchmark instances and give a detailed analysis of parameters, performance and behaviour. Keywords Meta-heuristic Local search Vehicle routing

When building simulations of complex systems the task of validation is often overlooked. Validation helps provide confidence in the simulation by exploring the link between the models that we build and the real complex system. We investigate software engineering validation techniques from outside the area of complex systems to assess their applicability for the types of simulation we build. We then provide an example of how such techniques can be applied to a complex systems simulation of cells migrating from blood vessels into lymph nodes through the walls of the blood vessels. We suggest that explicitly stating the modelling and simulation assumptions we make is key to the process of validation. Concluding, we highlight a possible process for validating complex systems that explicitly incorporates environmental aspects.

International audience; The relation between individuality and aggregation is an important topic in complex systems sciences, both aspects being facets of emergence. This topic has frequently been addressed by adopting a classical, individual versus population level perspective. Here, however, the frontiers that emerge in segregated communities are the focus; segregation is synonymous with the existence of frontiers that delineate and interface aggregates. A generic agent-based model is defined, with which we simulate communities located on grid and scale-free networked environments. Emerging frontiers are analyzed in terms of their relative occupancy, porosity, and permeability. Results emphasize that the frontier is highly sensitive to the topology of the environment, not only to the agent tolerance. These relations are clarified while addressing the topics of frontier robustness and the trade-off between its capacity to separate and allow exchange.

International audience; Modelling languages and thus their metamodels are subject to change. When a metamodel evolves, existing models may no longer conform to the evolved metamodel. To avoid rebuilding them from scratch, existing models must be migrated to conform to the evolved metamodel. Manually migrating existing models is tedious and errorprone. To alleviate this, several tools have been proposed to build a migration strategy that automates the migration of existing models. Little is known about the advantages and disadvantages of the tools in different situations. In this paper, we thus compare a representative sample of migration tools - AML, COPE, Ecore2Ecore and Epsilon Flock - using common migration examples. The criteria used in the comparison aim to support users in selecting the most appropriate tool for their situation.

International audience

UML notations require adaptation for applications such as Information Systems (IS). Thus we have defined IS-UML. The purpose of this article is twofold. First, we propose an extension to this language to deal with functional aspects of IS. We use two views to specify IS transactions: the first one is defined as a combination of behavioural UML diagrams (collaboration and state diagrams), and the second one is based on the definition of specific classes of an extended class diagram. The final objective of the article is to consider consistency issues between the various diagrams of an IS-UML specification. In common with other UML languages, we use a metamodel to define IS-UML. We use class diagrams to summarize the metamodel structure and a formal language, B, for the full metamodel. This allows us to formally express consistency checks and mapping rules between specific metamodel concepts. (C) 2007 Elsevier B.V. All rights reserved.

The Object Constraint Language (OCL) provides a set of powerful facilities for navigating and querying models in the MOF metamodelling architecture. Currently, OCL queries can be expressed only in the context of MOF metamodels and UML models. This adds an additional burden to the development and use of Domain Specific Languages, which can also benefit from an instance-level querying mechanism. In an effort to address this issue, we report on ongoing work on defining a rigorous approach for aligning the OCL querying and navigation facilities with arbitrary Domain Specific Languages to support instance-level queries. We present a case-study that demonstrates the usefulness and practicality of this approach., Electronic Communications of the EASST, Volume 5: OCL for (Meta-)Models in Multiple Application Domains 2006

We grow increasingly dependent on the appropriate operation of computer-based systems. One aspect of such systems is security. As systems become more complex current means of analysis will probably prove ineffective. In the safety domain a variety of analysis techniques has emerged over many years. These have proved surprisingly effective. Since the safety and security domains share many similarities, various authors have suggested that safety techniques might usefully find application in security. This report takes one such technique, HAZOPs, and applies it to one widely used informal design component – UML’s use cases.

International audience; no abstract

Grenoble, France, Janvier 2002

Volume LNCS 2068, Springer-Verlag

Elsevier, M. Dyer and M. Shepperd eds; International audience; no abstract

National audience; Our project is combining UML with the B formal method for the domain of data intensive information systems. It consists in extracting a subset of UML concepts suitable for the analysis of such systems, producing derivation rules from UML diagrams to B specifications and developping a prototype support tool. A preliminary step is to precisely define the syntax and semantics of the required UML notations. This is achieved using a metamodelling technique. In this article we present the specialised metamodels, in UML and B notations, for structural (class diagrams) and behavioural (state transition and collaboration diagrams) elements. Then we outline how the formal metamodel is used in the development of the tool.

We present an approach for change-based (as opposed to state-based) model persistence that can facilitate high-performance incremental model processing (e.g. validation, transformation) by minimising the cost of change identification when models evolve. We illustrate a prototype that implements the proposed approach on top of the Eclipse Modelling Framework and we present a roadmap for further work in this direction.

Iterated learning takes place when the input into a particular individual’s learning process is itself the output of another individual’s learning process. This is an important feature to capture when investigating human language change, or the dynamics of culturally learned behaviours in general. Over the last fifteen years, the Iterated Learning Model (ILM) has been used to shed light on how the population-level characteristics of learned communication arise. However, until now each iteration of the model has tended to feature a single immature language user learning from their interactions with a single mature language user. Here, the ILM is extended to include a population of immature and mature language users. We demonstrate that the structure and make-up of this population influences the dynamics of language change that occur over generational time. In particular, we show that, by increasing the number of trainers from which an agent learns, the agent in question learns a fully compositional language at a much faster rate, and with less training data. It is also shown that, so long as the number of mature agents is large enough, this finding holds even if a learner’s trainers include other agents that do not yet posses full linguistic competence.

International audience; Natural languages enable humans to engage in highly complex social and conversational interactions with each other. Alife approaches to the origins and emergence of language typically manage this complexity by carefully staging the learning paths that embodied artificial agents need to follow in order to bootstrap their own communication system from scratch. This paper investigates how these scaffolds introduced by the experimenter can be removed by allowing agents to autonomously set their own challenges when they are driven by intrinsic motivation and have the capacity to self-assess their own skills at achieving their communicative goals. The results suggest that intrinsic motivation not only allows agents to spontaneously develop their own learning paths, but also that they are able to make faster transitions from one learning phase to the next.

Experiments with worker termites constructing a royal chamber around a termite queen in species Macrotermes subhyalinus (Rambur) have shown that both trail and cement pheromones are involved and necessary for the successful formation of pillars during the building process. However, earlier models of the construction were able to demonstrate stigmergic pillar formation with cement pheromone alone. We present results from a new three-dimensional agent-based model, developed to investigate the role of trail pheromone in the construction process. The model is able to demonstrate how, if the properties of the cement pheromone are altered so that its attractive influence is more localised than in earlier models, termites are unable to produce significant pillar formation. The model shows how the addition of trail deposition and following effectively increases the range of the stigmergic effect so that pillar formation is restored. The presence of trail pheromone also results in pillars which are narrower than those produced by cement pheromone alone, and which show more pronounced lateral extensions. Additionally the paths that the termites take from the termite queen to building sites become more directed with time. These features are in keeping with observation and have not been previously modelled.

In this paper, we explore the emergence and direct interaction of two different types of dissipative structure in a single system: self-replicating chemical spot patterns and buoyancy-induced convection rolls. A new Lattice Boltzmann Model is developed, capable of simulating fluid flow, heat transport, and thermal chemical reactions, all within a simple, efficient framework. We report on a first set of simulations using this new model, wherein the Gray-Scott reaction diffusion system is embedded within a non isothermal fluid undergoing natural convection due to temperature gradients. The non-linear reaction which characterises the Gray-Scott system is given a temperature-dependent rate constant of the form of the Arrhenius equation. The enthalpy change (exothermic heat release or endothermic heat absorption) of the reaction can also be adjusted, allowing a direct coupling between the dynamics of the reaction and the thermal fluid flow.The simulations show positive feedback effects when the reaction is exothermic, but an intriguing, competitive and unstable behaviour occurs when the reaction is sufficiently endothermic. In fact when convection plumes emerge and grow, the reaction diffusion spots immediately surround them, since they require a source of heat for the reaction to proceed. Then however, the proliferation of spot patterns dampens the local temperature, eventually eliminating the initial convection plume and reducing the ability of the spots to persist. This behaviour appears almost ecological, similar as it is, to competitive interactions between organisms competing for the same nutrient source.

No abstract available.

Living systems are organised in space. This imposes constraints on both their structural form and, consequently, their dynamics. While artificial life research has demonstrated that embedding an adaptive system in space tends to have a significant impact on its behaviour, we do not yet have a full account of the relevance of spatiality to living self-organisation. Here, we extend the REDS model of spatial networks with self-organised community structure to include the “small world” effect. We demonstrate that REDS networks can become small worlds with the introduction of a small amount of random rewiring. We then explore how this rewiring influences a simple dynamic process representing the contagious spread of infection or information. We show that epidemic outbreaks arise more easily and spread faster on REDS networks compared to standard random geometric graphs (RGGs). Outbreaks spread even faster on randomly rewired small world REDS networks (due to their shorter path lengths) but initially find it more difficult to establish themselves (due to their reduced community structure). Overall, we find that small world REDS networks, with their combination of short characteristic path length, positive assortativity, strong community structure and high clustering, are more susceptible to a range of contagion dynamics than RGGs, and that they offer a useful abstract model for studying dynamics on spatially organised organic systems.

Silicon microchips of size 100x100 μm with active electronic sensing and actuation reacting in a chemical environment is the vision of the research project http://www. micreagents.eu, see figure 1a. These chips, called lablets, are fabricated in standard 180nm silicon technology and will be equipped with custom developed supercapacitors allowing them to react autonomously in fluids. They are designed to catalyze reactions with inbuilt electrodes and utilize electro-osmotic flow to propel along in the fluidic system, McCaskill et al. (2012).

We aim to better understand collective behaviours in social animals, doing so in the context of bio-hybrid societies, i.e., those that comprise robots and animals. Together, they make up a collective adaptive system, in which the self-organising patterns of the natural society can be understood, augmented and modified by the presence of robots. Here, we conduct a series of simulation-based experiments to investigate how natural behaviours in juvenile honeybees can be influenced by robots that are able to change key environmental stimuli. Firstly, we show specific couplings between animals and robots that can lead to symmetry-breaking and collective decision-making, even from an initially homogeneous environment. Secondly, we demonstrate that collective decisions made by animals in distinct habitats can be coordinated, through robots that share only relatively simple information between habitats. Such mixed animal-robot societies exhibit multiple interactions and feedback loops, the understanding of which is key to the design of engineered parts that successfully harness the potential of the overall complex system.

In the occam-pi programming language, the client-server communication pattern is generally implemented using a pair of unidirectional channels. While each channel's protocol can be specified individually, no mechanism is yet provided to indicate the relationship between the two protocols; it is therefore not possible to statically check the safety of client-server communications. This paper proposes two-way protocols for individual channels, which would both define the structure of messages and allow the patterns of communication between processes to be specified. We show how conformance to two-way protocols can be statically checked by the occam-pi compiler using Honda's session types. These mechanisms would considerably simplify the implementation of complex, dynamic client-server systems.

Distributing process-oriented programs across a cluster of machines requires careful attention to the effects of network latency. The MPI standard, widely used for cluster computation, defines a number of collective operations: efficient, reusable algorithms for performing operations among a group of machines in the cluster. In this paper, we describe our techniques for implementing MPI communication patterns in process-oriented languages, and how we have used them to implement collective operations in PyCSP and occam-pi on top of an asynchronous messaging framework. We show how to make use of collective operations in distributed processoriented applications. We also show how the process-oriented model can be used to increase concurrency in existing collective operation algorithms.

Communicating Sequential Processes (CSP) was developed around a formal algebra of processes and a semantics based on traces (and failures and divergences). A trace is a record of the events engaged in by a process. Several programming languages use, or have libraries to use, CSP mechanisms to manage their concurrency. Most of these lack the facility to record the trace of a program. A standard trace is a flat list of events but structured trace models are possible that can provide more information such as the independent or concurrent engagement of the process in some of its events. One such trace model is View-Centric Reasoning (VCR), which offers an additional model of tracing, taking into account the multiple, possibly imperfect views of a concurrent computation. This paper also introduces ''structural'' traces, a new type of trace that reflects the nested parallelism in a CSP system. The paper describes the automated generation of these three trace types in the Communicating Haskell Processes (CHP) library, using techniques which could easily be applied in other libraries such as JCSP and C++CSP2. The ability to present such traces of a concurrent program assists in understanding the behaviour of real CHP programs and for debugging when the trace behaviours are wrong. These ideas and tools promote a deeper understanding of the association between practicalities of real systems software and the underlying CSP formalism.

CSP processes have a static view of their environment -- a fixed set of events through which they synchronise with each other. In contrast, the pi-calculus is based on the dynamic construction of events (channels) and their distribution over pre-existing channels. In this way, process networks can be constructed dynamically with processes acquiring new connectivity. For the construction of complex systems, such as Internet trading and the modeling of living organisms, such capabilities have an obvious attraction. The occam-pi multiprocessing language is built upon classical occam, whose design and semantics are founded on CSP. To address the dynamics of complex systems, occam-pi extensions enable the movement of channels (and multiway synchronisation barriers) through channels, with constraints in line with previous occam discipline for safe and efficient programming. This paper reconciles these extensions by building a formal (operational) semantics for mobile channels entirely within CSP. These semantics provide two benefits: formal analysis of occam-pi systems using mobile channels and formal specification of implementation mechanisms for mobiles used by the occam-pi compiler and run-time kernel.

Writing concurrent programs in languages that lack explicit support for concurrency can often be awkward and difficult. Haskell's monads provide a way to explicitly specify sequence and effects in a functional language, and monadic combinators allow composition of monadic actions, for example via parallelism and choice two core aspects of Communicating Sequential Processes (CSP). We show how the use of these combinators, and being able to express processes as first-class types (monadic actions) allow for easy and elegant programming of process-oriented concurrency in a new CSP library for Haskell: Communicating Haskell Processes.

While we strive to create robust language constructs and design patterns which prevent the introduction of faults during software development, an inevitable element of human error still remains. We must therefore endeavor to ease and accelerate the process of diagnosing and fixing software faults, commonly known as 'debugging'. Current support for debugging occam-pi programs is fairly limited. At best the developer is presented with a reference to the last known code line executed before their program abnormally terminated. This assumes the program does in fact terminate, and does not instead live-lock. In cases where this support is not sufficient, developers must instrument their own tracing support, ``printf style''. An exercise which typically enlightens one as to the true meaning of concurrency... In this paper we explore previous work in the field of debugging occam programs and introduce a new method for run-time monitoring of occam-pi applications, based on the Transterpreter virtual machine interpreter. By adding a set of extensions to the Transterpreter, we give occam-pi processes the ability to interact with their execution environment. Use of a virtual machine allows us to expose program execution state which would otherwise require non-portable or specialised hardware support. Using a model which bears similarities to that applied when debugging embedded systems with a JTAG connection, we describe debugging occam-pi by mediating the execution of one execution process from another.

When teaching concurrency, using a process-oriented language, it is often introduced through a visual representation of programs in the form of process network diagrams. These diagrams allow the design of and abstract reasoning about programs, consisting of concurrently executing communicating processes, without needing any syntactic knowledge of the eventual implementation language. Process network diagrams are usually drawn on paper or with general-purpose diagramming software, meaning the program must be implemented as syntactically correct program code before it can be run. This paper presents POPed, an introductory parallel programming tool leveraging process network diagrams as a visual language for the creation of process-oriented programs. Using only visual layout and connection of pre-created components, the user can explore process orientation without knowledge of the underlying programming language, enabling a ''processes first'' approach to parallel programming. POPed has been targeted specifically at basic robotic control, to provide a context in which introductory parallel programming can be naturally motivated.

In this paper we address the automatic synthesis of controllers for the coordinated movement of multiple mobile robots. We use a noise-resistant version of Particle Swarm Optimization to learn in simulation a set of 50 weights of a plastic artificial neural network. Two learning strategies are applied: homogeneous centralized learning, in which every robot runs the same controller and the performance is evaluated externally with a global metric, and heterogeneous distributed learning, in which robots run different controllers and the performance is evaluated independently on each robot with a local metric. The two sets of metrics enforce Reynolds’ flocking rules, resulting in a good correspondence between the metrics and the flocking behaviors obtained. Results demonstrate that it is possible to learn the collective task using both learning approaches. The solutions from the centralized learning have higher fitness and lower standard deviation than those learned in a distributed manner. We test the learned controllers in real robot experiments and also show in simulation the performance of the controllers with increasing number of robots.