As Windows screen reader users will know, there is no screen reader included in Windows. Instead, users requiring a screen reader must obtain and install a third party product. Yes, there is Microsoft Narrator, but even Microsoft know that this is hardly worthy of the name "screen reader". :)

A few years ago, Apple revolutionised the accessibility industry by building a fully fledged screen reader, VoiceOver, right into Mac OS X. Ever since, many have asked why Microsoft can't do the same for Windows. Many are angry with Microsoft for this continued lack of built-in accessibility, some using it as support for the "why Apple is better than Microsoft" argument.

Here's some food for thought. I'm not sure Microsoft could do this even if they wanted to; their hands are probably tied in a legal sense. If they did, they could very likely be sued by assistive technology vendors for anti-competitive conduct, just as they have been sued several times concerning their bundling of Internet Explorer with Windows. Once again, Apple don't have to be concerned with this because there wasn't an existing screen reader on Mac OS X and they don't have the dominant position in the market.

I have no evidence for this argument. Perhaps I'm wrong, but history suggests that it is highly likely that I'm not.

Even as one of the lead developers of NVDA, I'm first and foremost a blind user who wants the best possible access, both for myself and other blind users. As such, I would very much welcome a screen reader built into Windows. Competition is good. A built-in screen reader doesn't mean that other screen readers can't exist. If the built-in solution were good enough, then there would be no need for NVDA to exist. If it weren't, NVDA would drive accessibility to improve through innovation and competition.

Since VoiceOver came to Mac OS X, many screen reader users have joyfully sung its praise - and there's certainly a lot to praise. Some who were previously Windows users have taken the plunge and moved to Mac OS X completely, never looking back. Others use both operating systems or perhaps dream of no longer being dependent on Windows for certain software. This is all fantastic, but as an NVDA developer, there are also aspects of this that frustrate and exasperate me.

Right from the start, NVDA has used "object navigation" in order to review the user interface, particularly to provide access to elements which can't be otherwise accessed using the keyboard. In short, every element in the user interface is generally represented by an object. These objects exist in a hierarchy or tree of objects. Object navigation allows the user to explore this hierarchy by moving between objects and then descending/entering/interacting with objects of interest. For example, entering a list would allow you to see its list items. This is in contrast to the "flat review" (or "screen review") method that Windows screen readers have traditionally used for review, whereby the user can review the content of the screen in a flat fashion from top to bottom, left to right, similar to the way a simple text document would be read. While this might seem more logical at first, it's worth remembering that a sighted user doesn't necessarily read the screen in this ordered fashion. Instead, they are more likely to focus on specific elements of interest, which in some ways is more akin to object navigation. As always, both methods have advantages and disadvantages.

On the Mac, there is only object navigation; there is no concept of flat review of the entire screen using the keyboard. (In the latest version of Mac OS X, you can explore the screen in this fashion using the trackpad. However, NVDA's tracking and reading of text under the mouse allows you to do something similar.) It seems that Mac users are quite happy with this approach, and yet we are constantly bombarded by NVDA users with complaints about the difficulty of object navigation and requests for flat review functionality in NVDA.

So, here's my question for those of you who are either full or partial Mac converts. Why is object navigation quite acceptable on the Mac, but yet not acceptable in Windows? It sometimes seems to me that some of the same users who frequently sing the praises of VoiceOver then turn and complain about the lack of flat review in NVDA. Perhaps I'm wrong and those users who want flat review would not be comfortable using VoiceOver. Even so, it sometimes seems that people are willing to accept a different approach on a completely new platform, yet are unwilling to accept it in a newer product on an existing platform. It's certainly true that NVDA's object navigation needs to be cleaned up a bit (removing extraneous objects, etc.), but I don't think this is the whole story.

ON the web, this gets even more interesting. Due to the non-linear fashion of web pages, Windows screen readers have had to provide their own "flat" representation of web pages. They then override the cursor and other keys to navigate within that representation. Aside from the technical issues associated with this, working with interactive controls on web forms requires a separate mode of interaction (named forms mode, focus mode, etc.) where the screen reader lets the user interact directly with the control by allowing cursor and other keys to pass straight through to the control. (Some screen readers can automatically switch to this mode when appropriate, but there are still two modes.) This is becoming more of a challenge with the ever growing number of web applications, where more keys are required to work with the application. Object navigation solves this problem because the cursor and other application keys are never overridden by the screen reader, so the screen reader doesn't interfere with the functionality of web applications.

Again, VoiceOver uses object navigation on the web and VoiceOver users appear to be quite happy with this. NVDA currently does what other Windows screen readers do, but again, would you be happy if we abandoned this approach in favour of object navigation? It would certainly solve this web application problem once and for all. I get the impression that NVDA users would be unhappy if we changed this.

I want to hear your thoughts. Comment here, Twitter or send me an email.