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in Mobile Computing Environments

Toshikazu Akagi

Scho ol of Information Science,

Japan Advanced Institute of Science and Technology

February 14, 1997

Keywords: Mobile computing, Real-Time Mach .

With the advance of technology, the portable computer have come smaller and p ow-

erful. Wecancarrythecomputer toeverywhereandcan use everytime withthenetwork

connection. Wecall these environmentsas\mobile computing environments", and it en-

ables very useful variety of computing. These ordinary mobile computers have PC card

slotsand batteries, sowecan usemanytyp esofdevices byinsertingPCcard devicesand

can use computers continuously withoutACadapters. By usingPC card devices, device

congurations of the computer is dynamically changewith inserting device orremoving.

And such mobile computers also have the APM (Advanced Power Management) BIOS.

APM enables to controlling powerof CPU, disks and any of devices of the mobile com-

puter. It also have managing function of batteries. By using APM, we can know about

remaining batteries, status of chargingand availability ofAC adapters.

By using thesedevices, the state of environmentsof computeris dynamicallychange.

It means that device congurations, remaining batteries and availability of AC adapter

be aect the execution of applications. It is very useful that applications dynamically

changebehavior toadapt to the environment.

In this paper, we propose a framework for building adaptive applications in mobile

computing environments.

Copyright c

1997byToshikazuAkagi

card devicesand APMdevice. It enablesthatoperatingsystemscan changedynamically

devicecongurationsbyinsertingaPCcardorremovingaPCcard,andwecangetstatus

ofbatteryoravailabilityoftheACadapter. SowealsoproposeEventManagerthatdeliver

events generated in the kernel to user-level servers. And propose Environment Server

architecture that deliver eventsneededby the application toapplications by ltering. In

this architecture, the lter of event can describe with the Tcl scripting language. By

inserting lters to the Environment Server , applications can receive events to change

behavior. Finally,wedescribesomeadaptiveapplicationsthatuse EnvironmentServer.

Environment Server provides agoo d abstraction for event typ es, resourcenames and

control ofsystem components. Wecan use pathnamestospecify events,resourcecontrol

when writing applications. With the using path names, we can access uniform to all of

the system resources. Forexample:

/localhost/pccard/event

/localhost/pccard/event/inserted

/localhost/apm/status/batt

/localhost/apm/control/suspend

Path names are construct from the host name, the comp onent name, event typ es,

statustyp esand controls. Andaneverypathobjecthas ascriptwrittenbyTcl scripting

language, and with casting to path objects applications can refer the resource. To get

events,application install ascripts specied apath name. Applications can also make a

conditions with specify a event and some resources in the scripts. For Example, we can

describe inscripts as follows:

path : /localhost/pccard/event/inserted

script: "if { [cast /localhost/apm/status/ac-online] == 1 } {\n

set ret \"card inserted and ac-online\"\n

}\n"

Whenwe specifythese scripts,applicationgetsnoticationwhen acardwasinsertedand

a batterystatus is ACon-line.

Environment Server architecture will provide these advances.

It enables delivereventseciency fromkernel to user-level server.

Byusing Environment Server, applications can referthe system resource.

And also, Environment Server provide a good abstractions to applications with

accessing eventtypes, resourcenames.

Environment Server user librariesprovidegoodway toaccess the server.

These character are able to advantage of building adaptive applications that using

events, referencing resources and controls. And it also provides to applications a go od

abstraction of events,resources and control.

The outline of this thesis is asfollows:

In chapter 1,weintroduce the outline of the this research.

We discuss the problems that why need adaptive applications and how to develop

adaptiveapplications insuchasmobile computing environments inchapter2.

Andwediscussworkrelatedtowritingadaptivesoftware usingsystem events,pro-

vidingabstractionofresourcestoapplications,anddevelopingadaptiveapplications,

inchapter3.

Weproposeaframeworkforbuildingadaptiveapplicationsinmobilecomputingen-

vironments in chapter 4. It Also describ e about modications to Real-Time Mach

Microkernel to supp ort PCcard devices and APM device, Event Manager that en-

ablesdelivereventstouser-levelprogramsanddescribetheoverviewofEnvironment

Server architecture.

Andthen, wedescribeabout Environment Server that providethe eventdelivering

mechanisms and abstractions of resources to applications, in chapter 6. We also

describ eab outthe scriptforwritingeventlters,interfacestoapplicationsanduser

librariesto support writingapplications.

In chapter 6, we show some examples using Environment Server to build applica-

tions. Andwediscuss about eects of our framework.

Finally,wewill conclude this thesisin chapter7.

ModicationstoReal-TimeMachMicrokernelsupportingPCcarddevicesandAPM

device.

Event Manager,itextensions kernel function.

Environment Server software.

Andsome of example applications( cardmonitor,esh, web control.)