Archive for the 'Content' Category

RDFa – Implications for Accessibility

Here are my initial thoughts on how I believe RDFa will benefit web accessibility. If you are new to RDFa I recommend reading the Wikipedia entry on RDFa and the W3C RDFa primer as an introduction.

A bit of background on RDFa

RDFa is a set of extensions to HTML and XHTML from W3C. With RDFa it is possible to use custom vocabularies to include machine readable data in web documents. In current web documents based on HTML or XHTML there are very limited ways of expressing information for machines. There are:

  • HTML elements that express document structure (e.g. headings, lists, tables), and rethoric (em, strong),
  • (broadly defined) HTML elements that express various technical terms (code, kbd, samp), and,
  • the content itself.

As more business domains are moving online the need to exchange data in a more structured fashion will increase. Instead of publishing data twice, once in a web document for humans and once in a separate file for machines, RDFa makes it possible to include machine readable data in web documents. (In a way, this has been possible since the modularization of XHTML, but in practice, few developers seem to have used the extension mechanisms of XHTML).

An RDFa example

Consider the following XHTML markup:

<p class="contactinfo">
	My name is Jo Smith. I'm a distinguished web engineer at
	<a href="http://example.org">Example.org</a>.
	You can contact me 
	<a href="mailto:jo@example.org">via email</a>.
</p>

Most humans will be able to understand the information but for machines this markup is too vague to parse without ambiguity. By providing more information about the content we can reduce this ambigity. First we provide information about our vocabulary in the HTML element:

<html xmlns:contact="http://www.w3.org/2001/vcard-rdf/3.0#">

Then we can use the terms of that vocabulary to provide more information for machines:

<p class="contactinfo" about="http://example.org/staff/jo">
	My name is
	<span property="contact:fn">Jo Smith</span>.
	I'm a
	<span property="contact:title">
		distinguished web engineer
	</span>
	at
	<a rel="contact:org" href="http://example.org">
		Example.org
	</a>.
	You can contact me
	<a rel="contact:email" href="mailto:jo@example.org">
		via email
	</a>.
</p>

One of the major benefits is that there is a standard for the vocuabulary specification and it is machine readable. You can open the URI for the vcard vocabulary used above in your browser (you may have to “view source” to see it) and see more information about the terms of the vocabulary. Another big advantage is that you can create a vocabulary specification for your business domain yourself and publish on the web. You do not have to put it through some central authority.

We have now modified the markup in our document to make it useful for both humans and machines. The document still looks the same for sighted users that look at the information in their web browser. Apart from the added benefit for search engines and desktop applications (e.g. importing this information into your adressbook now becomes easier) I believe it will have interesting implications for assistive tools as well.

What if assistive software could use RDFa information?

Since the vocabuary is created in a machine readable format it should be possible to let assistive software such as screen readers load the vocabulary specification and provide more information for the user. If you look at the vocabulary specification for vcards used above each term has a label text. For the title the specification looks like this:

<rdfs:label>Position Title</rdfs:label>

One of the simplest ways of using this information is of course to read it to the listener during the linearization of the page. Since a term can have a description too even more information could be provided to the user.

In practice, the sequence of events for a screen reader working on top of a web browser could look like this:

  1. Browser opens the web page.
  2. Screen reader parses the HTML and extracts references to all external vocabularies.
  3. External vocabularies are fetched and parsed for labels and descriptions.
  4. The screen reader announce that extended information exists and starts rendering the page.

So, by using RDFa to reduce ambiguity for machines it is likely that humans too can benefit from the added information. It will be very interesting to see what makers of assistive tools can come up with. What other use cases for RDFa with regards to accessibility can you see?

References

For more information on RDFa see:

Mental Workload for Paged and Scrolled Documents

In a recent doctoral thesis from the department of psychology at Gothenburg University, Sweden, Erik Wästlund provides some interesting findings on mental workload for consumption of information. Two of the principal findings are:

  1. Consumption of information is more efficient when information is presented on paper compared to presenting the information on a computer screen.
  2. Consumption of information generates less mental workload when the page layout is adapted to fit the screen.

The first point may not come as a surprise. Steve Krug has argued that users tend to scan web pages rather than read them and Erik’s study cites previous research that says users tend to have difficulties reading longer passages of text on a screen.

A fundamental characteristic of reading information on a computer screen is that it “involves both the process of reading the presented text and handling the computer. The reader’s processing capacity is being utilized not only for decoding but also for page navigation.”. When we read e.g. a book the mental workload is low because we know from experience where to focus after turning a page.

Adapting content to the screen

The second point has some interesting implications for people working with the web. Currently, web pages with a lot of text tend to come in two flavors:

  1. All text on a single web page and the standard browser scrollbar to move forward in the page. (Example: A review of the Web Content Accessibility Guidelines 2.0, May 2007 Working Draft).
  2. Paged text and one or more navigation buttons to move to the next page. (Example: Mark Pilgrim’s Dive Into Accessibility, Day 6: Choosing a DOCTYPE).

Paged text on the web today is rarely adapted to the browser window size.

In Erik’s study the test subjects were given reading assignments. One group read the document in a scrolled format (number 1 above) and the other group read the document in a paged format where the page format was adapted to the computer screen.

The result showed that mental workload was lower when you read information in a paged way adapted to the screen. This is interesting as the current technology for constructung web pages (HTML and CSS) do not provide an easy way to page text adapted to the user’s screen. I am guessing that it may be possible by using javascript to measure the window size and create keys to move forward by a viewport page at the click of a button.

On the other hand, most browsers provide this functionality for scrolled pages in the Page-up and Page-down keys. In the usability tests I have participted in during the past years I can not recall a single user using the Page-up/down keys.

So, does this mean that scrolled text is better if user’s learn to navigate with the Page-up/down keys? Or should content authors paginate long documents? Will these methods have other accessibility implications?

Visually Editing Semantics – What You See Is What You Mean

Many CMSs (content management systems) come with some kind of visual editor that allow editors to create and format content without knowing the markup involved. I evaluated some of these WYSISYG-editors back in March and found most of them lacking in features for semantic markup. One of the more commonly found problems is that they have a lot of features for visual formatting like font selection, font color, indentation etc. In most CMSs these are features you would like to avoid (ask your corporate communication department if they would like to have features that allow editors to go crazy with colors on the website…).

Som of you will argue that one should never use a WYSIWYG editor and instead deploy a wiki-style editing syntax like e.g. Markdown. This typically solves the problem, but in reality this type of syntax is very difficult for content editors to learn and becomes increasingly difficult if you want to do more advanced editing.

WYMeditor to the rescue

I was planning to start working on my own inline editor by forking TinyMCE and correcting what I thought was wrong with it when I found this comment from Jean-François:

[...] I’d like to present WYMeditor: WYMeditor is a web-based XHTML editor, not WYSIWYG, but WYSIWYM: the end-user can concentrate on rich content, while layout and design are handled via style-sheets.

This sounded almost too good to be true. WYSIWYM (What You See Is What You Mean) is of course how content for the web should be edited. WYMeditor is in an early stage of development, but after playing with it for a while it looks very promising. If it guarantees well formed XHTML it is an easy task to convert it to HTML 4.01 or any other representation you can think of.

WYMEditor interface showing the markup structure of a text.

Currently it works in Internet Explorer and Gecko-based browsers such as Firefox. You can try an online demo of WYMeditor here.

If content management systems were to use editors like WYMeditor web accessibility would get and instant boost. There are some issues that hopefully will be solved soon:

  • icons for strong emphasis and emphasis look like bold and italics,
  • heading levels can be mixed in a non-logical way (like inserting h5 after h1)
  • support for som elements like acronym, abbreviation and definition lists, are missing

But, if I was developing a CMS I would definitely monitor the progress of WYMeditor.

Could WYMeditor make content editors aware of semantics in a way currently impossible in other inline editors? Will this type of inline editing merge with visual presentation à la XStandard?

Don’t Provide an Accessibility Statement

When I surf the web I see more and more sites providing an accessibility statement. Googling for “accessibility statement” returns over twelve million pages. What do these statements contain? Why would you want one? Who reads them? This article will try to make two points: 1. accessibility statements are often pointless and 2. you are better off with a “site help” if you think your target audience need it.
Read more about Don’t Provide an Accessibility Statement

Methods for measuring text readability

Content is often overlooked when working with a web site to increase accessibility. Even if your web site follows all W3C recommendations it will still be inaccessible if your content is difficult to comprehend. Let’s have a look at how you can measure text readability in english, spanish, swedish, danish and french to get a feel for the readability of your content.

Read more about Methods for measuring text readability

Peter Krantz, peter.krantz@giraffe.gmail.com (remove giraffe).