OSGi

The OSGi Alliance (formerly known as the Open Services Gateway initiative) is an open standards organization (logo).

Over the past few years it has specified a Java-based service platform that can be remotely managed. The core part of the specifications is a framework that defines an application life cycle model and a service registry. Based on this framework, a large number of OSGi Services have been defined: Log, Configuration management, Preferences, Http Service (runs servlets), XML parsing, Device Access, Package Admin, Permission Admin, Start Level, User Admin, IO Connector, Wire Admin, Jini, UPnP Exporter, Application Tracking, Signed Bundles, Declarative Services, Power Management, Device Management, Security Policies, Diagnostic/Monitoring and Framework Layering.

• R1 released in May 2000
• R2 released in October 2001
• R3 released in March 2003
• R4 released in October 2005

In the following more details about the history, the specification and the community acceptance are provided.

Scope

The Framework implements an elegant, complete, and dynamic component model - something that is missing in standalone Java/VM environments. Applications or components (coming in the form of bundles for deployment) can be remotely installed, started, stopped, updated and uninstalled without requiring a reboot - management of Java packages/classes is specified in great detail. Life cycle management is done via APIs which allow for remote downloading of management policies. The service registry allows bundles to detect new services, or the going away of services, and adapt accordingly.

The original focus was on service gateways but the applicability turned out to be much wider. The OSGi specifications are now used in applications ranging from mobile phones to the open source Eclipse IDE. Other application areas include cars, industrial automation, building automation, PDAs, grid computing, entertainment(e.g. iPronto), fleet management and application servers.

Classification: OSGi & System-Layering

Specification Process

The OSGi specification is developed by the members in an open process and made available to the public free of charge and without licensing conditions. The OSGi Alliance has a compliance program that is open to members only. As of April 2006, the list of certified OSGi implementations contains 10 companies.

Organization

The Alliance has been founded by Sun Microsystems, IBM, Ericsson and others in March 1999 (after it was first called the Connected Alliance).

Among its members are (as of April 2006) more than 35 companies from quite different business areas, for example IBM, Nokia, Motorola, Philips, BenQ, Siemens VDO, Telefonica, BMW, Gatespace Telematics, ProSyst and Deutsche Telekom.

The Alliance has a Board of Directors for the respective working areas. For each area there also are so-called Officers. On the commercial side cooperation takes place in different committees, while technical issues - like developing the specification further, from Release 1 over 2 and 3 to R4 - is handled by the existing Expert Groups.

There are dedicated Expert Groups for the areas Mobile, Vehicle and Core Platform. A new group (EEG) is planned to address Enterprise side applications.

Community

In October 2003, Nokia, Motorola, ProSyst and other OSGi members formed a Mobile Expert Group (MEG) that will specify a MIDP-based service platform for the next generation of smart mobile phones, addressing some of the needs that CLDC cannot manage - other than CDC. MEG became part of OSGi as with R4.

Also in 2003 Eclipse selected OSGi as the underlying runtime for the plug-in architecture used for the Eclipse Rich Client Platform and the IDE platform. Eclipse itself includes sophisticated tooling for developing OSGi bundles and there are a number of other Eclipse plug-ins aimed at supporting OSGi behaviour (e.g. both ProSyst and Knopflerfish have Eclipse plug-ins available specifically for OSGi developers).

There is a vibrant free software community revolving around the OSGi specifications. See Equinox OSGi, Apache Felix and Knopflerfish OSGi.

News in OSGi Release 4

The new features of OSGi R4 in brief are as follows :

• Powerful new modularization capabilities providing enhanced encapsulation of networked services that can share a single VM.
• Modularized class sharing and hiding of implementation details.
• Advanced handling of multiple versions of the same classes so old and new applications can execute within the same VM.
• Localization of OSGi bundle manifests enabling service deployment anywhere.
• Enhancements in security and policies: The new Conditional Permission Admin service provides an elegant and simple way to manage networked services securely. It also supports dynamic policies that can depend on external (custom) conditions. Combined with R4 support for digital signatures, this provides a central security solution to large deployments of products using the OSGi Service Platform.
• A Declarative Services specification that addresses memory footprint issues that can prevent small embedded devices from using a service oriented architecture to support multiple applications. Additionally, it significantly simplifies the service-oriented programming model by declaratively handling the dynamics of services.
• Compatibility with Release 3, requiring no changes for existing OSGi bundles, applications, or services.

Blogs

• OSGi Blog - blog of the official "OSGi Evangelist"
• Fun with OSGi - A blog about OSGi bundle development etc.
• aQute OSGi Technologies - A blog about OSGi and Java technology

References

• OSGi web site General Information
• Specification Download
• Developer site
• Javadoc of the release 4
• OSGi Service Platform, Release 3, IOS Press, ISBN 1-58603-311-5

Guidance and Information Exchange

• Frequently Asked Questions
• OSGi World Congress and Developer Forum
• aQute: OSGi Info - Information about OSGi and access to seminars
• OSGi Users Forums - Japan, Korea, and soon : France, Spain, Italy, Germany

Vendors and Implementations

• IBM WebSphere Everyplace Deployment - Complete end to end platform enabling OSGi developers to build configurable, disconnectable, managed, applications and services for desktop, mobile, and embeddable clients delivering web, ajax, and/or rich user interfaces
• ProSyst Software GmbH - Leading OSGi Software Provider for Remote Management and Service Delivery
• Knopflerfish OSGi - Open Source OSGi implementation under BSD license
• Gatespace Telematics - Leading OSGi vendor, provides Knopflerfish Pro, the fully supported version of open source Knopflerfish.
• Equinox OSGi - Open Source OSGi implementation under EPL license
• Objectweb Oscar: An OSGi framework implementation - Open Source OSGi framework implementation under BSD license
• Apache Felix: An OSGi framework implementation - Open Source OSGi framework implementation under ASL2 license
• Concierge OSGi - Lightweight Open Source implementation under BSD license, ideal for mobile and embedded systems.
• Oxygen Project
• Jadabs - A dynamic lightweight container for small devices in a distributed environment
• Connected Systems, Inc - Leading Provider of OSGi Solutions and Services in South Korea
• osxa - Open Source OSGi implementation under EPL license
• R-OSGi Project - Lightweight OSGi extension for discovering and accessing distributed services.
• Newton - Open Source OSGi based distributed component framework
• Infiniflow - OSGi based Distributed Service Platforms for SOA Applications
• Bundles repositories : Alliance, Oscar v1 and v2, Knopflerfish

Related RFCs and Java Standards

• RFC-2608 (Service Location Protocol)
• Sun JINI™ (Java Intelligent Network Infrastructure)
• Sun JCP JSR-8 (Open Services Gateway Specification)
• Sun JCP JSR-232 (Mobile Operational Management)
• Sun JCP JSR-246 (Device Management API)
• Sun JCP JSR-249 (Mobile Service Architecture for CDC)
• Sun JCP JSR-277 (JavaTM Module System)
• Sun JCP JSR-291 (Dynamic Component Support for JavaTM SE)

Related Technology Standards

• MHP / OCAP
• Universal Plug and Play (UPnP)
• HomePlug
• LonWorks
• CORBA
• CEBus
• EHS / CECED CHAIN
• X10