Thread Subject: Re: dialog on OS-platform-application
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From: Gregg Vanderheiden
Date: Mon, Oct 23 2006 10:30 AM
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This topic (who is responsible for what) was addressed in the HFES 200.2
and in parallel in ISO 9241-171. There the term "platform" was used for
software that supported other software. And application was used for end
See below for specifics
Gregg C Vanderheiden Ph.D.
Users of this standard will need to consider all the recommendations that it
contains. In many cases the application of a recommendation may depend on
the particular context of use so that it will be necessary to determine
whether a given piece of guidance is applicable.
This standard is designed to support those responsible for all the aspects
of developing and acquiring software that will be accessible. This will
involve people with different roles and with responsibility for different
aspects of the process. In order to assist the reader in identifying
whether a given clause applies to those parts of the system for which they
have responsibility, a way of categorizing where the guidance needs to be
applied has been developed and is described in Table 1.
Table 1 - Implementation responsibility
(the operating system and associated layers, and toolkits)
Operating system, drivers and associated software layers.
Includes Windowing Systems, libraries and associated toolkits that provide
or affect the user interface of other software (e.g. GNOME, KDE, Java
runtime, Visual Basic, applications executing scripts or hosting embedded
NOTE: If a software program uses its own routine to override or replace OS
driver functions then the application would need to conform to related
Platform Software provisions.
(which run on and make use of services provided by platform software)
Software not considered as part of the operating system or its immediate
layers. This includes "desktop" software bundled with an operating system,
personal productivity applications, development tools, Web browsers, and
other non-OS software.
Hardware or software that is added to or incorporated within a system that
increases accessibility for an individual. Some portions may function as
platform software while other portions may function as application software
and would be covered above. Guidelines for the design of assistive
technology in general are outside the scope of this document.
Since it is often ambiguous to differentiate between Platform and
Application and since most of the provisions apply to both, we only note
those provisions that would apply to only one or the other.
In order to achieve accessibility it is necessary to provide support in
different parts of the overall software system. While much can be done to
improve accessibility in the design of the application, it is not possible
to provide all of the input and output support that users require in every
circumstance at the application level alone. To the extent that any
particular part of the software is dependent upon a level below it for its
operational characteristics it will be necessary to ensure that the lower
levels enables the implementation of recommended accessibility
characteristics in any layers that depend upon them. This dependency may
occur in relation to different layers in the platform software and in
relation to the applications that are mounted on the platform software.
Applications themselves may have layers that result in dependencies arising
within different levels of the application. The majority of the
recommendations in clauses 8, 9, 10, and 11 require that the issue be
addressed at more than one level of the software system if the particular
recommendation is to be satisfied. In some cases the guidance is related to
either the platform software or applications layers alone. The platform
software is the general means by which accessibility features that involve
control of hardware devices, in particular those involving input, are
implemented and controlled. Some issues that arise in relation to the nature
of the content and the form of its presentation may only apply within the
Many recommendations marked are the responsibility of both applications and
portions of the platform software that have or affect a user interface.
Developers of operating systems, toolkits, and other platform components are
encouraged to implement support for these provisions in ways that minimize
the amount of work required by application developers. Application
developers may take advantage of such features where they are available, but
are ultimately responsible for ensuring their products are compatible with
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