AN OSGi BASED MOBILE DEVELOPMENT OVERVIEW

Pascal Suetterlin, Olaf Thiele and Hartwig Knapp

Chair in Information Systems III, University of Mannheim, L5,5 , 68131 Mannheim, Germany

Keywords:

OSGi, Mobile Architectures, Overview.

Abstract:

This paper presents an overview of the three most promising platforms for developing mobile applications:

Titan (Java), Google Android and the iPhone. While the Titan platform already implements most design goals,

Google’s Android platform is in an early development stage. The iPhone platform lacks most functionality,

but will soon be enhanced by a new ﬁrmware. The main focus in our comparison lies on the deployment and

management of applications through the Open Services Gateway Initiative (OSGi) framework.

1 INTRODUCTION

Following the immense success of mobile applica-

tions for the consumer market, much research in the

recent years has focused on mobile applications to

support the business side of mobility. Most projects

assumed that processing power as well as the devel-

opment environment on mobile devices are very lim-

ited. With the introduction of new mobile platforms

these assumptions might have to be altered. In this pa-

per we present the three most promising mobile plat-

forms on the market: Sun Java, Google Android and

Apple iPhone. All platforms offer numerous possibil-

ities, but as one of the main aspects of past research

consisted of dynamically deploying and managing ap-

plications, we focus on this area.

The OSGi speciﬁcation described below has these

features as its main building blocks. Both deployment

and management proved to be hard to implement in

the past due to the need to access many functions of

the underlying operating system. OSGi aims at pro-

viding these basic functions for mobile applications

across several device speciﬁcations. Taking the view-

point of a potential developer for a dynamically load-

ing application we present what modern platforms are

capable of as well as how they conform to the OSGi

standard. For both classical cell phones (formerly

J2ME) and the new Google Android platform OSGi

implementations are available and described below.

2 TECHNICAL CONTEXT

This section describes the technical context surround-

ing the OSGi approach.

2.1 Service Oriented Architecture

Due to the increased complexity and size of mobile

applications there is a high motivation to implement a

Service Oriented Architecture (SOA) in both personal

and enterprise environments. Moreover, the growing

number of mobile devices calls for more abstract ar-

chitecture implementations like SOA. Simply speak-

ing, SOA enables programmers to build software ap-

plications composed of loosely coupled components

(Duda et al., 2005). Deployed applications need to

be suited to the user’s requirements, to the resources

of his/her Input/Output device and to the surround-

ing environment (e.g. context). Deployment refers

to all activities following the development of the soft-

ware which make it available to the user/device (Ayed

et al., 2006). These activities consist of installing and

conﬁguring of the software but can also include soft-

ware reconﬁguration, updates or even un-installing it.

One of the main beneﬁts of a SOA in networked sys-

tems is that it reduces signiﬁcantly the overall com-

plexity of building, managing and deploying applica-

tions. Many of the technical requirements for a SOA

are covered by an OSGi implementation.

245

Suetterlin P., Thiele O. and Knapp H. (2008).

AN OSGi BASED MOBILE DEVELOPMENT OVERVIEW.

In Proceedings of the International Conference on Wireless Information Networks and Systems, pages 245-248

DOI: 10.5220/0002027502450248

 SciTePress

2.2 OSGi

The Open Services Gateway Initiative (OSGi) has

been actively developing its speciﬁcations for almost

10 years and aims at implementing a lightweight

framework for deploying and managing applica-

tions in service oriented architectures (OSGiAlliance,

2007). The OSGi Service Platform was built for the

consumer market and the alliance has already de-

ﬁned a speciﬁcation for mobile devices such as smart-

phones and PDAs in 2006. Based on the newly cre-

ated version OSGi 4 Nokia and others launched the

JSR 232 which is implemented by the Sprint Titan

Platform as described below. The OSGi framework

creates a host environment for deploying and manag-

ing bundles and the services they provide (Hall and

Cervantes, 2004). A Bundle is a plain jar-ﬁle with a

special format manifest ﬁle which is speciﬁc to the

framework. Bundles are organized hierarchically. It’s

possible that one application uses another bundle or

exports its own packages.

Besides the bundle-mechanism the OSGi stan-

dard describes a layer of four levels which provide

the different functions as described in the speciﬁca-

tions. These are the ”L0 - Execution Environment”,

”L1 - Module”, ”L2 - Life-cycle” and ”L3 - Service

Model”. The ﬁrst layer L0 consists of the minimum

execution environment so that almost every Java-

enabled device could implement the framework. This

layer can even be executed on older J2ME devices.

The next layer L1 implements the concept of bundles

that uses classes from each other in a controlled way

according to system and bundle constraints. The man-

agement mechanism provided by the framework in

layer L2 allows installation, activation/deactivation,

update and removal of the bundles without restarting

the virtual machine. The ﬁnal layer L3 describes the

part which provides the publish/ﬁnd/bind services.

3 COMPETING

ARCHITECTURES

In this section we highlight the speciﬁcities of the

three platforms covered in this paper: Titan as a typ-

ical Java implementation, Google Android and the

relatively new Apple iPhone. We start off with a

short introduction into the Java VM. Figure 1 gives

an overview of the OSGi implementations:

3.1 Mobile Java

Java 2 Micro Edition, which is meant for low memory

consumer devices, provides a run-time environment

for applications implemented in a stripped-down ver-

sion of the Java language (Lund and Norum, 2004).

The software implementations on the mobile devices

differ from the reference implementation for desk-

top computers(J2SE) of Sun Microsystems and re-

sult in incompatibilities. Details can be found in the

speciﬁcation (J2ME, 2005). In addition to the min-

imal J2ME components called ”Connected Limited

Device Conﬁguration” (CLDC), the ”Mobile Infor-

mation Device Proﬁle” (MIDP) offers in version 2.0

new features such as an enhanced user interface, mul-

timedia and game functionality, greater connectivity,

over-the-air (OTA) provisioning, and end-to-end se-

curity (Sun, 2006). Some vendors implement more

functionality deﬁned in Java Speciﬁcation Requests

(JSR). This could be Bluetooth support (JSR-82) or

access to the locally stored contacts (JSR-75). Nokia,

for example, took the so called lead in several JSRs to

standardize their implementation efforts.

In this context we make use of the ”Connected De-

vice Conﬁguration” (CDC), that runs on the most re-

cent cell phones as full implementations of a Java vir-

tual machine. It already utilizes the JSR-232 which

is the Java speciﬁcation of the OSGi framework core

and mobile speciﬁcations. In contrast to existing

MIDP applications, this implementation can make use

of servlets, allows for better graphical programming

(games) and has direct access to the phone’s hard-

ware. The older CLDC and MIDP standards will

probably give way to the fully J2SE compliant CDC.

However, it has recently been stated that ”the integra-

tion of OSGi with a Java EE environment is challeng-

ing as both technologies want to take control of the

Java runtime” (Kaegi and Deugo, 2008). This might

hold true for mobile applications as well.

3.2 Sprint Titan Platform

The Titan platform by Sprint (developedtogether with

Nokia) offers built in support for OSGi through a

JSR-232 speciﬁcation and is therefore an existing im-

plementation of the JSR. Furthermore, it is already

included in the Windows Mobile SDK for Smart-

phones. Another advantage is, that the architecture

is openly accessible. Legacy applications are run as

classical MIDP applications, whereas OSGi bundles

are run by the CDC VM. Generally, bundles are run

in the background. The present Titan version sup-

ports the following application models: plain old MI-

Dlets (POM), OSG bundles and deployment packages

(DPs) and Eclipse embedded Rich Client Platform ap-

plications (eRCP). Future application models include

OAMs (OSGi aware MIDlets) or widget based web

applications.

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246

Figure 1: Competing Architectures and their OSGi Implementation.

A key OSGi concept of Titan is the possibility to

manage applications at run time. This can be done

remotely through the OMA-DM protocol. All neces-

sary development ﬁles are supplied as Eclipse plug-

ins. The plug-in aids in launching the VM, deploying

applications and bundles as well as using a built-in

proﬁler for debugging. As Titan is a true OSGi im-

plementation, most software written beforehand can

easily be ported to the platform. Effort for deploy-

ment and management is therefore minimal.

In a business context the Sprint platform can be

seen as a full OSGi implementation. It is justiﬁed

to say that other vendors will follow. Especially

given the fact that CDC allows for standard Java pro-

gramming instead of building specialized (cut down)

versions with Sun’s mobile J2ME platform. Two

competitors in this area are the relatively new An-

droid platform by Google and the very popular Apple

iPhone. Both are described in the following sections.

3.3 Android

Originally the company Android Inc. worked on a

novel (supposedly simpler) platform for mobile ap-

plication development. While Sun tries to overcome

the limitations of J2ME by introducing J2SE (Java

Standard Edition) features with CDC, Android offers

a simpler unifying approach. Google bought Android

in 2005 and thus drew public attention to the project.

In 2007 Google founded the Open Handset Alliance

together with LG, Motorola, Samsung and others in

order to develop an open mobile platform. This Al-

liance focused on the development of the so called

”GPhone”. Even though no mobile deviceis yet avail-

able, it can be seen as a competitor to Nokia’s market

power.

The Android platform builds upon a Linux ker-

nel, uses Apache Harmony, offers several APIs and

runs through a newly developedvirtual machine name

Dalvik VM. Through this setup, Google avoids pay-

ing the Java licensing costs for mobile devices. Even

though the Dalvik VM draws heavily from the Java

world. Dalvik source code follows the Java syntax,

but offers different mobile APIs. The Android dx tool

offers to port existing Java byte code to executable

Dalvik byte code. Thus, existing Java source code

can easily be ported to Dalvik source code. Gen-

eral Dalvik APIs include SQLite (one of the small-

est database systems), OpenGL, SAX-Handler, Blue-

tooth (BLUEZ), JSON and a WebKit to run a browser

(e.g. Safari).

Apache Felix is the successor of the Oscar open

source project and implements the OSGi release 4

core framework speciﬁcation (Felix, 2008) for gen-

eral use on Java platforms. Its goal is to provide

a completely compliant implementation of the OSGi

framework speciﬁcation. Through its almost J2SE-

Standard JVM it’s possible to run Apache Felix with

only a few alterations (Offermans, 2007) on Android.

Thus, Android implements OSGi. In the next section

we present the iPhone platform.

3.4 iPhone

The iPhone platform has been developed for the Ap-

ple iPhone. The iPhone combines functions like me-

AN OSGi BASED MOBILE DEVELOPMENT OVERVIEW

247

dia player, mobile smartphone, digital camera and In-

ternet access in one device. Thus we speak of the

iPhone as both the physical device as well as the mo-

bile platform architecture. Comparing to Android, the

iPhone platform currently renounces the Java technol-

ogy due to licence fees which are around 5 - 10 Dol-

lar per device. The operating system is an reduced

Mac OS X (Leopard) which needs about 700MB disk

space. The scope of operations is limited compared

to the desktop version but uses an Linux-kernel (Dar-

win) with an modiﬁed development framework (Co-

coa) that supports touchscreen abilities.

Among a lot of helpful features the iPhone has

main limitations in application development compar-

ing to other devices. First, the iPhone has no Java

virtual machine available, all applications are written

in Objective-C. Second, there is currently no possibil-

ity to deploy an application to an iPhone. Facing this

drawback, Apple announced launching the SDK 2.0

in 2008. Developers are then able to send their ap-

plications to Apple and distribute it via the AppStore

software which will cause costs for both, developers

and users. Another option to bring an application on

the iPhone today is to ”jailbreak” it. During this pro-

cess some security key functions are disabled so that

downloading iPhone applications from third parties

like regular developers becomes possible. Of course,

the claim for warranty expires immediately. Hence,

this is not an acceptable option to deploy applications

in a business context, but it might be alright for re-

search purposes. Apple will provide some more key

features for the iPhone which are absolutely necessary

for the application development process.

4 CONCLUSIONS

We presented the three most promising mobile plat-

forms for dynamically deploying and managing appli-

cations available today. At ﬁrst we looked at Sprint’s

Titan platform which has a built-in OSGi implemen-

tation according to JSR 232. One of the design goals

of the platform was the abililty of an SOA-oriented

framework. In our opinion Titan is a powerful plat-

form for dynamic distribution and collaboration of

software components and applications. There is also

support for the Eclipse embedded Rich Client (eRCP)

application model which means that rich GUI applica-

tions can run across a broad range of devices. A major

drawback is that there is only a Windows Mobile im-

plementation which means a limited device selection.

The second platform presented, Google An-

droid, has no built-in OSGi-Framework. We con-

sidered some OSGi-implementations such as Eclipse

Equinox, Apache Felix and Knopﬂerﬁsh. Due to the

lack of available hardware, we could only test Apache

Felix in the emulator of Android SDK.

The iPhone SDK as our last platform has no

ofﬁcial mechanism for application distribution yet.

Through the business model of the iPhone Apple

wants to take a ”small” amount of the sales from third-

party applications. Apple created a so called App-

Store to make application delivery as simple as pos-

sible and wants to add it in the next iPhone ﬁrmware.

After completion, it should be possible to bring a

JVM to the iPhone (as announced from Sun). The

next step would be to port a OSGi-implementation to

the iPhone. When that task is completed then it would

be possible to use the OSGi-frameworkon the iPhone.

From hardware aspects Android could also run on the

iPhone. We hope that our insights on present OSGi

implementations will help further research.

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