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Re: RS: Write a proposal for the Techniques Document for loading an assistive technology for direct access to the browsers DOM

From: Al Gilman <asgilman@iamdigex.net>
Date: Sun, 30 May 1999 12:49:10 -0400
Message-Id: <Version.32.19990530114141.01100950@pop.iamdigex.net>
To: WAI UA group <w3c-wai-ua@w3.org>
At 12:45 AM 5/30/99 -0400, Harvey Bingham wrote:
>At 1999-04-12 01:04 PM, Rich Schwerdtfeger wrote:
>>Access to application specific data across process boundaries can be costly 
>>in terms of performance. Also, access to the DOM through a specified 
>>accessibility API inhibits the ability for assistive technologies to access 
>>object model data not yet provided in that API. Therefore, user agents
>>provide a mechanism to load an assistive technology (AT) into the process 
>>space of the application, as a separate thread, with direct access to the 


>Suspicious but unknowing: Isn't this a way for a Trojan horse to get into 
>the user agent? Does ..., as a separate thread, ... give enough protection? 
>I worry that a user agent needs to give arbitrary AT (unknown in advance)
>access to the UA innards.


Yes, any extension mechanism has to be engineered for security as though it
is a potential avenue of attack.  That is just goes with the territory, it
does not mean we shouldn't seek appropriate extension mechanisms.  The
state of practice in this regard is that extension mechanisms are supported
and they have occasional security breakdowns.  All of them.  They are still


>>A technique for accomplishing this would be to store a reference to an 
>>assistive technology in a system registry file or properties file in the
>>of Java. Registry files are common among many operating system platforms


>So who controls what can get into the Registry? It is my understanding that
>a principal cause of Windows crashing is lack of control over what gets into

>the registry, and who can break common information in it to change values
>to whatever they desire, breaking what other programs need.


Giving the user the ability to tailor the user interface of all
applications class-by-class, based on some resource ontology (dictionary of
types or classes of presentable information) is pro-usability and

Mark Novak nominated the following resources as good tutorial explanation
of the Model-View-Controller architectural view which I think we need to
understand here as well as in designing the details of protocols and formats:



Be careful to get the whole URL from two text lines in those references.

Yes, people experience problems with the  Windows registry, but the use of
such a central [to the system or user account] UI-building database is
still a positive step.  The problem is not the existence and role of the
Registry, but the logical  model that it implements.  That is what we are
exploring here.  If the Registry supported seamless AT integration, how
would it work?

Microsoft may not respond immediately with a total rewrite of Windows, but
I suspect that if there is an accessibility advantage to something which
Java provides, they want to understand it to see if Windows can't provide a
comparable capability.


>>In Java 2, the existence of an accessibility.properties causes the system 
>>event queue to check the file for assistive technologies required for
>>If the file contains a property called assistive_technologes, it will load 
>>all registered assistive technologies and start them on there own thread in 
>>the Java Virtual Machine which is a single process. An example entry for 
>>Java is as follows:


>I'm dense here:    an  accessibility.properties  
>(is there such? is it a collection?)
>typo: ...called assistive_technolog_i_es, ...


>>Once the assistive technology is determined from the registry, any user
>>on the given operating system can now determine if an assistive technology 
>>needs to be loaded with their application and load it.


>Does this preclude more than one AT to be available? Are there times where
>more than one are required: such as both braille and speech output?, or
>voice command and special keyboard?


If I read Rich right, the system loads "all ATs registered" as needed for
the class of the object being accessed.  That sounds as though multiple ATs
(such as concurrent disposition to both Braille and speech) can be supported.

If multiple ATs are to be loaded, they have to be designed and tested for
compatibility; they can't make contradictory assumptions.  This is a
necessary part of the extension mechanism (discipline, as used) that is
mostly separate from the 
real-time transaction where an object is opened and ATs appropriate to its
class are linked in as a result.  

Actually, both your concerns point to a single place.  The time to check
the compatibility status of a pair of ATs is when registering them both to
the same class of resource object.


>>Rich Schwerdtfeger
>>Lead Architect, IBM Special Needs Systems
>>EMail/web: schwer@us.ibm.com http://www.austin.ibm.com/sns/rich.htm
>>"Two roads diverged in a wood, and I -
>>I took the one less traveled by, and that has made all the difference.",
>What a joy to find that saying on a rock in the woods on a farm that Frost
>once had [Now a Vermont state park, I believe], and having the choice he 
>probably had in mind.
>Regards/Harvey Bingham
Received on Sunday, 30 May 1999 12:44:08 UTC

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