Symbian OS System Definition

Overview

We provide here information to complement that in the Symbian OS System Definition. That paper categorises the high level system definition components, relating these to availability on Symbian OS phones. But it does not go into detail about the contents of these components. We present here a more detailed description. We also indicate how their composition has changed between OS releases. Finally it is explained how this information now enables SDK users to work out for themselves which APIs in the Symbian Developer Library are available on any particular Symbian OS phone.

Symbian OS phones and UI platform

Even a cursory review of the Symbian OS phones which have thus far been launched or announced shows the flexibility of Symbian OS to support a wide range of mobile phone products targeted at diverse markets. From the viewpoint of the software developer, the rapid expansion of the target market for Symbian OS phones, combined with the openness of the platform to third party applications and services represents a clear business opportunity.

However the diversity of products which has made possible the rapid market penetration of Symbian OS phones also offers a challenge to software developers, in that the software platform which application developers must target is not defined uniquely by Symbian OS. In particular, Symbian OS is created with a provisional user interface (called TechView) intended only for testing and reference usage. This UI must ultimately be replaced by a user interface suited for shipping on mobile phones. Not only that, a number of applications, system services, device drivers etc. need to be provided alongside Symbian OS for a phone to be produced.

To avoid the difficulties which would otherwise ensue if Symbian OS phone development were allowed to take place in an arbitrary way, Symbian introduced the concept of UI platforms. Each UI platform provides a distinct UI for Symbian OS and an associated set of system applications for such tasks as messaging, browsing, telephony, multimedia and contact/calendar management. These applications typically make use of generic application engines provided by Symbian OS. UI platforms intended to support the installation of third party applications written in native C++ have to be supported by SDKs which define developer platforms based on that UI platform. There are currently four such UI platforms, with as a result four flavours of SDK:

• Nokia Series 60
• Nokia Series 80 (previously "9200 communicator series")
• Nokia Series 90
• UIQ

Phone manufacturers build their phone based on a particular UI platform, licensing or writing for themselves any essential phone software or device drivers required and any other custom software they wish to bundle with their phone. To target a particular Symbian OS phone, the independent software developer needs to know which developer platform (or SDK) is appropriate. This can be ascertained from the Symbian Developer Network web site. This information does not in itself define the phone's software capabilities. But since the further system software which has to be provided to build a phone typically does not have an application-level API or else doesn't make such an API public, such changes will usually not be of particular significance for the developer.

System Definition

This is not however the whole story. In practice it has proved necessary to allow some leeway for Symbian OS licensees to modify, omit or replace Symbian OS system software in a UI platform. Further the same can happen to the UI platform software when it is incorporated into a phone. Changes or omissions in relation to Symbian OS software components designed for deployment on Symbian OS phones are controlled by a categorisation scheme whereby all such software is categorised under one of the following heads, depending on how core the software component is:

These allow licensees varying degrees of flexibility, as is explained in Symbian OS System Definition. In that paper can also be found information about the extent to which each of the Symbian OS phones released thus far based on a UI platform has exercised this flexibility incorporating changes which affect the availability of published Symbian OS APIs. As it turns out licensees' policies in this regard are driven mainly by a desire maximally to reuse Symbian OS system software components where possible. The constraints associated with the categorisation seldom come to bear.

No similar policy has been published in relation to reuse of UI platform software in phones, but in practice any differences between phones and their associated SDKs are fairly clear and predictable in terms of the API set made available to third party developers. Further details about such differences are best obtained from licensees' developer support Web sites.

In the present paper we shall build on the information presented in Symbian OS System Definition. This latter paper should be seen as a complement to this one. It provides a high level statement of which system definition components belong to each of the above system definition categories:

We shall provide here a much more detailed breakdown of each of these system definition components into lower-level system components. For each system component we shall indicate also the executables it is composed of. In terms of Table 3, we will be filling out the bottom two rows.

We will show at the same time how the composition of each system component and system definition component has changed between OS releases from version 6.0 to the current version 8.0. For each system component we also clarify the accessibility of the associated API. There are three levels of accessibility:

• Public
  There is an API published in the Symbian Developer Library which third party developers can take advantage of. The component may in addition have other interfaces which are not intended for third party usage.
• None
  There is no API associated with this component as it provides functionality invoked only by system code, for example to carry out conversions.
• Partner only
  There is a programming interface associated with this component but it is intended only for Symbian Platinum Partner or licensee usage. Availability or replacement of such components on Symbian OS phones does not affect the development platform for third party developers.

Notice that components associated with Symbian's Java implementation have not been included below. Since this provides no public API for native apps, it is immaterial to the question addressed here about public API support for native development.

It will be seen that the information below, taken together with that readily available in each edition of the Symbian Developer Library concerning which executable exports each public API, it becomes possible to associate each public API with a unique system definition component. Further, with reference to the Symbian OS System Definition paper, it can be ascertained which of the currently available Symbian OS phones support each API. Such information should be of considerable help to developers targeting multiple Symbian OS phones.

System Categorisation

Common Symbian

ETEL server
UIKON
Application utilities
Kernel
File server
User libraries
ESOCK server
TCP/IP
C32 server
Window server
INSOCK
TLS
Mbuf manager
Root server

Common Replaceable

ont/bitmap server
Screen drivers

Optional Symbian

Calendar engine
vCard and vCal
Contacts engine
Database engine
GSM SMS Stack
Help
Task scheduler
Bio Messaging
Internet mail MTM
Messaging Engine
HTTP Client
Internet Protocols
SyncML
FORM Layout engine
Store
Bluetooth® wireless technology
COMMS logging
IrDA
Cryptography library
Comms channels

Optional Replaceable

Fax MTM
Onboard converters
Other app engines
Wserv plugin
On-board connectivity
PC Connectivity Toolkit
Alarm/World Server
Locales
Logging engine
System agent
MMS
WAP-browser engine
WAP Stack
Browsing Framework
Application Level Internet Protocols
Data-type recognisers
Code converters
Grid layout engine
Printer drivers
View server
Power
C standard library
Comms database
Media server
Multimedia
Comms utilities
Networking options
FTP, Telnet
Security
Content handling framework