DiaSim: A Parameterized Simulator forPervasive Computing Applications

Wilfried Jouve, Julien Bruneau, Charles ConselINRIA / LaBRI / ENSEIRB, Talence, France

jouve@labri.fr, bruneau@enseirb.fr, consel@labri.fr

Abstract—Pervasive computing applications involve both soft-ware concerns, like any software system, and integration con-cerns, for the constituent networked devices of the pervasivecomputing environment. This situation is problematic for testingbecause it requires acquiring, testing and interfacing a variety ofsoftware and hardware entities. This process can rapidly becomecostly and time-consuming when the target environment involvesmany entities.

In this demonstration, we present DiaSim, a simulator for per-vasive computing applications. To cope with widely heterogeneousentities, DiaSim is parameterized with respect to a descriptionof a target pervasive computing environment. This description isused to generate both a programming framework to develop thesimulation logic and an emulation layer to execute applications.Furthermore, a simulation renderer is coupled to DiaSim toallow a simulated pervasive system to be visually monitored anddebugged.

I. INTRODUCTION

Pervasive computing applications coordinate a variety ofnetworked entities collecting context data from sensors and re-acting by triggering actuators. To collect context data, sensorsprocess stimuli that are observable changes of the environment(e.g., fire and motion). Developing a pervasive computingapplication requires to address a number of issues such asentity heterogeneity, physical constraints, and types of stimulipresent in the target environment. Also, such an applicationneeds to implement strategies to manage a variety of scenariose.g., fire situations, intrusions, and crowd emergency-escapeplans. Consequently, in addition to the challenges of develop-ing any software system, a pervasive computing system needsto validate the application building blocks both individuallyand globally, to identify potential conflicts. In practice, themany parameters to take into account for the development ofa pervasive computing application can considerably lengthenthis process and a fully-equipped pervasive computing envi-ronment is still required to run and test an application. As aresult, an iteration process is needed, involving the physicallayout of the target environment and the application code. Thisprocess is cumbersome and hinders testing applications againsta wide range of scenarios. To ease this process, we proposeDiaSim, a parameterized simulator for pervasive computingapplications.

II. OUR APPROACH

DiaSim relies on the DiaGen approach [1], [2] where ahigh-level specification of a pervasive computing environmentwritten in the DiaSpec language is passed to a compiler to

produce a customized programming framework. This program-ming framework provides developers with high-level abstrac-tions to discover services and to communicate with them.In the DiaSim approach, DiaGen automates the productionof simulation environments, enables transparent simulation ofapplications and allows actual entities to be tested togetherwith simulated ones. In the rest of this section, we describethe key features of our approach.Parameterized simulator. Pervasive computing systems tar-get a variety of application areas, including home automation,building surveillance and assisted living. A simulation toolfor the pervasive computing domain is required to deal withdifferent application areas, enabling new classes of entities andstimuli to be introduced easily. To adapt to various applicationareas, the DiaSim simulator is parameterized with respect to ahigh-level specification of a pervasive computing environmentwritten in the DiaSpec language.Transparent simulation. Our approach makes it possible forthe same code to be simulated or executed in the actualenvironment. DiaSim emulate the execution of an applicationwithout requiring any change in the application code. As aresult, when the testing phase is completed, the applicationcode can be uploaded as is and its logic does not requirefurther debugging. To do that, we ensure a functional corre-spondence between a simulated environment and an actual oneby requiring both implementations to be in conformance withthe same DiaSpec specification.Generated simulation support. A DiaSpec specification isused to generate both an emulation layer to execute ap-plications and a simulation programming framework to de-velop simulated entities. Furthermore, simulation scenariosare defined in a scenario editor which is parameterized bya DiaSpec specification. Simulated services and stimuli canthen be graphically defined using a wizard. To facilitate thecreation of simulated services and stimulus producers, weprovide libraries of predefined behaviors.Hybrid simulated environments. DiaSim builds simulatedenvironments as extensions of actual environments. Because ofthis inheritance strategy, an application can be executed in anhybrid environment, combining simulated and actual services.This feature is particularly useful to perform unit testing ofactual entities.Simulation renderer. We present a simulation renderer thatenables the developer to visually monitor and debug a per-vasive computing system. The simulation renderer takes into

account various features of the pervasive computing domain.Specifically, it supports visual representations for an open-ended set of entities and stimuli, visual support for scenariomonitoring, and debugging facilities to navigate in scenariosin terms of time and space.

The DiaSim simulator architecture is shown in Figure 1.Stimulus producers emit stimuli of various types accordingto a predefined scenario. In place of actual sensors, simulatedones process these stimuli and produce events. The unchangedapplication reacts to these events by invoking actuator com-mands. In turn, actuators change the simulated environment,triggering stimulus producers.

Emulator

Simulated Sensors

Simulated Actuators

Applicationsevents

Monitoring Engine

ScenarioController

StimuliProducers

StimuliProducers

StimuliProducers

StimuliProducers

StimulusProducers

stimuli

stimuli state

commands

Simulator of context

Monitor

Simulation Renderer

Logs

simulation data

Fig. 1. The DiaSim simulator architecture

III. DEMONSTRATION

To demonstrate the key features of DiaSim, we will simulatevarious applications in the building management area. DiaSimwill be used to test these applications and evaluate the feasi-bility of their deployment in ENSEIRB, an engineering schoolto which the authors are affiliated.

A. Target environment

The ENSEIRB school is a three-floor building of 13,500 m2,consisting of several lecture halls, labs and recreation roomsfor students. ENSEIRB hosts up to 900 occupants, includingstudents and faculty members. Many devices compose theENSEIRB school. Sensors such as motion detectors, light andtemperature sensors provide context information from all overthe building to various applications. The applications triggerseveral types of actuators. These include alarms, lights, LCDscreens, PDAs, loudspeakers and air conditioners.

B. Demonstration Steps

Specifying simulated environments. The first step of ourdemonstration will show how the DiaSim simulator is pa-rameterized with respect to the DiaSpec specification of theENSEIRB environment. We will show how to model a perva-sive computing environment in DiaSpec and how the resultingDiaSpec specification parameterizes the DiaSim simulator.

Defining simulation scenarios. The second step of ourdemonstration will be the definition of simulation scenarios.Scenarios will be defined using a Java GUI called the scenarioeditor (Figure 2). From a DiaSpec specification, simulatedservices are either graphically defined using a wizard, ordeveloped using the generated simulation programming frame-work. The demonstration will show examples of both ways todefine simulated services. The scenario editor also supportsthe definition of stimulus producers by allowing the user todefine stimulus intensities in areas of the simulated space atspecific moments in time. For example, a producer of motionstimuli simulates a user moving in a school hallway at agiven time. Furthermore, the definition of simulation scenariosis supported by libraries of generic simulated services andstimulus producers which can be parameterized following thetarget simulation scenario.

To see how the applications behave in a realistic environ-ment, the simulated scenario defines hundreds of simulatedpersons moving around in the school. The simulated personsare students and faculty members. Students belong to one offour departments at ENSEIRB. Their behavior depends on theagenda of their study field. When a class they have to attendbegins, they go to the class room. Furthermore, they modifythe context of the simulated environment. For instance, asimulated person is detected when passing in front of a motiondetector. As another example, simulated persons increase theCO2 density in the room where they are located.

Fig. 2. The scenario editor

Testing applications. Using the programming frameworkgenerated from a DiaSpec specification, we developed vari-ous applications which will be shown in our demonstration.In the third step, these applications will be tested againstthe previously defined simulation scenarios. Each applicationrequires several simulated services. To follow the evolutionof the simulated environments, DiaSim extends an existingvisualization tool: the Siafu open source context simulator 1.Siafu provides a 2D rendering and time-control functionalities.

1http://siafusimulator.sourceforge.net/

Figure 3 shows the resulting simulation renderer. Servicesand stimuli defined in the scenario are displayed on top of apicture of the simulated space. The simulation renderer givesthe state of services by displaying a bubble of raw text aboveservices and/or modifying the visual representation of theservice. To complement these macroscopic views, we enrichedSiafu’s rendering functionalities with Web Interfaces and audiostreams. As shown in Figure 3, in the ENSEIRB simulation,clicking on school LCD screens runs a Web interface showingits display. Similarly, loudspeakers are rendered using audiostreams.

Actual Devices

Actual Web Interfaces

Simulation Renderer

Fig. 3. Demonstration of a hybrid simulated environment

Demonstrating hybrid simulated environments. One ofthe key feature of DiaSim is to enable hybrid simulatedenvironments, i.e., combining simulated and actual devices inthe same simulation scenario. As illustrated in Figure 3, in thefinal step, we will demonstrate this feature by making actualdevices interact with simulated ones. These actual devicesare an IP camera and an actual PDA. The camera is usedas a motion detector for the intrusion manager. Messages arereceived on the actual PDA when an intrusion in the simulatedenvironment is detected. These actual devices will be addedincrementally in the simulation, demonstrating the flexibility

of our approach.

C. Demonstrated Applications

The first application is a newscast manager. Its purpose isto display news and schedules on screens scattered throughoutthe school. This manager reads the school RSS feed in orderto get the latest school news. It also receives schedule eventsfrom the ENSEIRB agenda. This agenda describes the coursesof the four ENSEIRB departments. The newscast manageralternatively displays the news and the students’ schedule. Akey feature of the newscast manager is that it adapts the con-tents displayed on the screens with respect to the departmentaffiliation and the nationality of the people surrounding thescreens. Thus, for instance, the messages displayed on a screenare in English if this screen is mainly surrounded by Englishnative speakers. Moreover, when a class begins, the newscastmanager plays a message on the loudspeakers of the schoolusing the text-to-speech technology.

The second application is an intrusion manager. It is ac-tivated when ENSEIRB is closed. The intrusion managerreceives intrusion events from the motion detectors. They areinstalled in every corridor and room of the school. When amotion is detected, the intrusion manager turns on the schoolalarms. It also displays a message on the PDA of the schoolsupervisor to warn him and to indicate where the intrusiontook place.

The last application is a building automation manager. Thismanager controls the lights depending on the outside lumi-nosity and the area occupancy. It also controls the school airconditioners to regulate the temperature based on temperaturevalues produced by multiple temperature sensors. When theschool is closed, all lights are turned off and the targettemperature is lower (in winter) or higher (in summer) thanduring the day to save energy. Between 7 am and 8 pm, itsbehavior depends on luminosity values of the outside lightsensors. If the luminosity is lower than a predefined threshold,the lights of a given area are turned on, when some peopleenter this area, and turned off, when the area is empty. If theoutside luminosity is greater than the predefined threshold, theprevious behavior only occurs for areas without windows. Themanager also receives information from CO2 sensors. Whenthe CO2 density is too high in a given area, the correspondingair conditioner is activated to decrease its density.

D. Technical constraints

The demonstration does not have special requirements otherthan a demo booth or table and an Internet connection.

REFERENCES

[1] W. Jouve, N. Palix, C. Consel, and P. Kadionik. A SIP-based program-ming framework for advanced telephony applications. In Proceedings ofthe 2nd LNCS Conference on Principles, Systems and Applications of IPTelecommunications (IPTComm’08), Heidelberg, Germany, July 2008.

[2] W. Jouve, J. Lancia, N. Palix, C. Consel, and J. Lawall. High-levelprogramming support for robust pervasive computing applications. InProceedings of the 6th IEEE Conference on Pervasive Computing andCommunications (PERCOM’08), Hong Kong, China, March 2008. WiPsession.