An interesting question in QTI history came up in discussion amongst the QTI IPS group recently and I thought I'd answer via my blog rather than email.
In QTI, you may use either the <img> element or the <object> element to include images in questions. But in some cases only <object> will do. In the words of the question put to me:
"The rule appears to be that declaration as img is used where the XHTML is to be passed on to (say) a browser for display, but declaration as an object is used where more complex handling is required."
Why?
Both <object> and <img> are valid ways of including an image in XHTML - during spec development Safari would render them if you just pointed it at the QTI without any processing!
However, at the time of writing <object> was considered the better way to include images with <img> being the legacy method common in HTML files. As with many efforts to regularize practice this hasn't really caught on as much as the HTML working group hoped!
Anyway, as a result of the above, where we wanted to accept an image and nothing else (i.e., in certain graphic interactions where issues like bounding rectangles, click-detection and the like needed to be simple and well defined) we chose the <object> form and not the <img> form.
This doesn't stop you putting images in runs of text in places like simpleChoice where layout is not critical. And the width and height can be put on both <img> and <object> to hint at desired rendering size. In both cases the attributes are optional as most rendering engines can use the default dimensions drawn from the media file itself.
But note that the <img> element has no way to specify the media type, which does place a burden on the rendering engine if it needs to sniff the image size because it will have to use file extension heuristics, magic bytes or similar to determine the type of file before it is able use it. These are the little things that cause bugs: <object> requires the media type so it wins there too.
At first glance, <object> seems to lack the accessibility features of <img> as it has no alt text. But it does provide a fairly rich way of handling platform limitations and accessibility needs, the rule being that the contents of the element should be used as a fallback if the object itself is not suitable. There is an issue here with its use in QTI. We chose <object> because we wanted to force people to use an image, not a text-flow. In graphic questions drag-and-drop style renderings are common and this is much harder with random chunks of HTML. But if the image is of a format that the browser does not support will a rendering agent use the fallback rules and what happens if they end up with a text flow anyway? QTI is silent on this but I would not rely on any fallback content when <object> is used in graphical interactions for one of its special purposes. If a delivery engine can't show the objects in a graphical question it should seek an alternative question, not an alternative rendering, in my opinion.
By the way, in the case of <gapImg> we explicitly added a label attribute alongside the <object> to make it clear that, if a label is given by the author it should be shown to all candidates and not treated as a more accessible alternative. Which brings me on to the issue of alt text in assessment generally...
When I first left university I seriously considered working as a graphic artist, so speaking from this limited experience I feel entitled to say that however much you think of your drawing skills others may not recognize your 'dog', 'cat' or even your 'boa constrictor digesting an elephant' (Google it if you are curious). If in doubt, a label is a good idea for everyone.
2011-08-23
2011-07-17
Using gencodec to make a custom character mapping
One of the problems I face in the QTI migration tool is markup that looks like this:
In XML the charset used in a document is detected according to various rules, starting from information available before the XML stream is parsed and culminating in the encoding declaration in the XML declaration at the top of the file:
For this reason, the use of the charset parameter in QTI version 1 is of limited value, at best it might provide a hint on an appropriate font to use when rendering the element. This is not a huge problem these days but when QTI v1 was written it was common for document renderings to be peppered with large squares indicating that the selected font had no glyph for the required character. These days renderers are smarter about selecting default fonts enabling developers to display arbitrary unicode text.
So you would think that charset is redundant but there is one situation where we do need to take note: the symbol font. The problem is explained well in this article: Symbol font – Unicode alternatives for Greek and special characters in HTML. The use of 'greek' in the QTI v1 examples is clearly intended to indicate use of the symbol font in a similar way - not the use of the 'greek' codepage in ISO-8859. The Symbol font is used a lot in older mathematical questions, you can play around with the codec on this neat little web page: Symbol font to Unicode converter.
According to the above article the unicode character representing the lower-case letter 'p', when rendered in the symbol font actually appears to the user like this: π - known as Greek small letter pi.
The problem for my Python script is that I need to map these characters to the target unicode forms before writing them out to the QTI version 2 file. This is where the neat gencodec.py script comes in. I don't know where this is documented other than in the gencodec source file itself. But this is a very useful utility!
The synopsis of the tool is:
So I downloaded the following mapping to a directory called 'codecs' on my laptop:
Then I ran the gencodec script:
And confirmed that the mapping was working using the interpreter:
In previous versions of the migration tool I didn't include symbol font mapping because I thought it would be too laborious to create the mapping. I was wrong, future versions will do this mapping automatically.
<mattext>The circumference of a circle diameter 1 is given by the mathematical constant: </mattext> <mattext charset="greek">p</mattext>
In XML the charset used in a document is detected according to various rules, starting from information available before the XML stream is parsed and culminating in the encoding declaration in the XML declaration at the top of the file:
<?xml version = "1.0" encoding = "UTF-8">
For this reason, the use of the charset parameter in QTI version 1 is of limited value, at best it might provide a hint on an appropriate font to use when rendering the element. This is not a huge problem these days but when QTI v1 was written it was common for document renderings to be peppered with large squares indicating that the selected font had no glyph for the required character. These days renderers are smarter about selecting default fonts enabling developers to display arbitrary unicode text.
So you would think that charset is redundant but there is one situation where we do need to take note: the symbol font. The problem is explained well in this article: Symbol font – Unicode alternatives for Greek and special characters in HTML. The use of 'greek' in the QTI v1 examples is clearly intended to indicate use of the symbol font in a similar way - not the use of the 'greek' codepage in ISO-8859. The Symbol font is used a lot in older mathematical questions, you can play around with the codec on this neat little web page: Symbol font to Unicode converter.
According to the above article the unicode character representing the lower-case letter 'p', when rendered in the symbol font actually appears to the user like this: π - known as Greek small letter pi.
The problem for my Python script is that I need to map these characters to the target unicode forms before writing them out to the QTI version 2 file. This is where the neat gencodec.py script comes in. I don't know where this is documented other than in the gencodec source file itself. But this is a very useful utility!
The synopsis of the tool is:
This script parses Unicode mapping files as available from the Unicode
site (ftp://ftp.unicode.org/Public/MAPPINGS/) and creates Python codecmodules from them.
So I downloaded the following mapping to a directory called 'codecs' on my laptop:
ftp://ftp.unicode.org/Public/MAPPINGS/VENDORS/APPLE/SYMBOL.TXT
Then I ran the gencodec script:
$ python gencodec.py codecs pyslet converting SYMBOL.TXT to pysletsymbol.py and pysletsymbol.mapping
And confirmed that the mapping was working using the interpreter:
$ python
Python 2.7.1 (r271:86882M, Nov 30 2010, 09:39:13)
[GCC 4.0.1 (Apple Inc. build 5494)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> unicode('p','symbol')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
LookupError: unknown encoding: symbol
>>> import pysletsymbol
>>> reg=pysletsymbol.getregentry()
>>> import codecs
>>> def SymbolSearch(name):
... if name=='symbol': return reg;
... else: return None
...
>>> codecs.register(SymbolSearch)
>>> unicode('p','symbol')
u'\u03c0'
>>> print unicode('p','symbol')
πIn previous versions of the migration tool I didn't include symbol font mapping because I thought it would be too laborious to create the mapping. I was wrong, future versions will do this mapping automatically.
2011-07-13
In Memoriam Claude Ostyn: Account Suspended
It is strangely saddening to have to mourn a professional colleague twice but today I noticed for the first time that one of my 'go to' sites for information on SCORM has finally also been laid to rest (this is perhaps old news).
Fortunately much of the information is preserved by archive.org but the strength of his voice seems strangely diminished there:
2011-07-11
Open Source Routers to the Rescue!
I spent a few happy hours this weekend fiddling with routers and stumbled across a great open source project called dd-wrt. This one is not for the timid as there is a serious risk of bricking your router but if you are anything like me you have an old box gradually filling up with discarded routers you are keeping just in case you main router fails.
I recently switched tariffs with my broadband supplier, Virgin Media. As a result, they replaced my cable modem with an all-in-one wireless-router/cable modem. I can see that this simplifies their business for most customers but when you already had a good router before it is a pain when you realise that you are now tied to something with poorer range and and annoying tendency to make your printer panic.
Anyway, as a result I went and bought an ASUS device (RT-N12) capable of being used as a wireless repeater to improve coverage in those hard-to-reach corners of my small 3-bed semi. Unfortunately, try as I might I could not get it to work as advertised. At one point I actually got it to repeat the wifi signal from the Virgin router but the LAN ports were all on their own private network. My attempts to fix the LAN ports broke wifi connectivity for everyone in the house and almost bricked the device. I updated to the latest ASUS firmware but still no joy - I was beginning to get bored of the recovery mode procedure for restoring factory defaults. There has to be a better way, surely?
Part of the problem is that the ASUS device has attempted to simplify the user interface of the router to an extreme making it very hard to fix issues. The quality of the translation in the UI is very poor and the little help icon almost always brings up a little box with placeholder text explaining what the help function does, rather than actually providing any useful insight into the settings. The one saving grace is that, with so few settings to control, one can quickly exhaust all possible combinations and conclude that home-networking is not for mere mortals.
But, masochists take note: there is even more fun you can have with these devices and you don't need to spend a penny more (the RT-N12 is available from £28 at 52 stores according to Google).
The software distributed by dd-wrt is a replacement firmware that actually works. Don't be scared off by the use of 'beta' or the frightening stories of bricked devices. I'm sure there is a reason why you are supposed to use the special ASUS firmware updating tool on Windows but I just flashed the firmware through Safari from my Mac and within a few minutes I was looking at a whole new user interface. This software is a breath of fresh air. It may be free but there is more documentation than the supplied firmware and being German the quality of the English is better than I could write myself.
I recently switched tariffs with my broadband supplier, Virgin Media. As a result, they replaced my cable modem with an all-in-one wireless-router/cable modem. I can see that this simplifies their business for most customers but when you already had a good router before it is a pain when you realise that you are now tied to something with poorer range and and annoying tendency to make your printer panic.
Anyway, as a result I went and bought an ASUS device (RT-N12) capable of being used as a wireless repeater to improve coverage in those hard-to-reach corners of my small 3-bed semi. Unfortunately, try as I might I could not get it to work as advertised. At one point I actually got it to repeat the wifi signal from the Virgin router but the LAN ports were all on their own private network. My attempts to fix the LAN ports broke wifi connectivity for everyone in the house and almost bricked the device. I updated to the latest ASUS firmware but still no joy - I was beginning to get bored of the recovery mode procedure for restoring factory defaults. There has to be a better way, surely?
Part of the problem is that the ASUS device has attempted to simplify the user interface of the router to an extreme making it very hard to fix issues. The quality of the translation in the UI is very poor and the little help icon almost always brings up a little box with placeholder text explaining what the help function does, rather than actually providing any useful insight into the settings. The one saving grace is that, with so few settings to control, one can quickly exhaust all possible combinations and conclude that home-networking is not for mere mortals.
But, masochists take note: there is even more fun you can have with these devices and you don't need to spend a penny more (the RT-N12 is available from £28 at 52 stores according to Google).
The software distributed by dd-wrt is a replacement firmware that actually works. Don't be scared off by the use of 'beta' or the frightening stories of bricked devices. I'm sure there is a reason why you are supposed to use the special ASUS firmware updating tool on Windows but I just flashed the firmware through Safari from my Mac and within a few minutes I was looking at a whole new user interface. This software is a breath of fresh air. It may be free but there is more documentation than the supplied firmware and being German the quality of the English is better than I could write myself.
The ASUS device clearly has software shortcomings but it isn't clear when linkingWifi devices which party is to blame. The market always seems to be getting ahead of the standards and even with the faster 802.11n mode it seems that devices can't agree which frequency to talk on and that in practice most networks are operating at b/g speeds for legacy reasons.
Routers like the Virgin hub are understandably configured for compatibility so most people seem to recommend turning off the wireless completely and then using one of the four LAN ports to plug in a completely separate wireless infrastructure to split new 'n' devices from the old b/g - now where is that box I keep all my old routers in...
2011-06-27
Amount of profanity in git commit messages per programming language
I spotted this blog page from a list I subscribe to the other day, those sensitive to profanity should look away now others can see the stats here...
Given that C# and Java are similar in many ways and are often used for the same things it is amusing that they both induce exactly equal levels of profanity in their developer communities.
The figures for different languages are significantly different (with C++ being the most sweary language to work in it seems) so I feel like this data is trying to tell us something.
And who are the nicest people to program with? PHP developers it seems (with Python not far behind).
2011-06-24
Visual C++ Redistributable Licensing: I'm just not seeing it
As part of putting together the latest builds of the QTI Migration tool I have had to repackage the updated tool into a new installer.
The migration tool is written in python and uses the py2exe tool to convert the Python script into a set of binaries that can be distributed to other Windows systems as a ready-to-run application without requiring Python (and various other packages, including wxPython: used for the GUI) to be installed first.
The output of py2exe is a folder containing the executable and all its supporting files ready to package up. Originally this was all done by Pierre, my co-chair of the QTI working group. I'm happy to report that updating the installation scripts went fine and I've been able to create a new Windows Installer using InnoSetup.
There is a recipe for using py2exe with wxPython published on pythonlibrary.org called "A py2exe tutorial". However, I did have one problem with this recipe - I too had trouble with MSVCP90.dll but I needed the help of stackoverflow (thread: py2exe fails to generate an executable) to actually get the build going. Once done, I was concerned with the warning messages about the need to have a license to redistribute the DLL in my installer. I found another blog post on distributing python apps for the windows platform which spelt out my options. As I don't personally own a Visual Studio license it seems like I need to use the redistributable package which can be downloaded from Microsoft.
Unfortunately, when I download this file the license in the resulting installer does not appear compatible with packaging it into my installer for distribution with my tool.
Several people on the net seem to suggest that the DLL is off-limits but the 'redistributable' does exactly what it says on the tin. Indeed, if you don't run the package it isn't clear what license you signed up to by downloading it but once you run the installer it clearly says that "You may make one backup copy of the software. You may use it only to reinstall the software." and that you may not "publish the software for others to copy". So I've played safe and am crossing my fingers that my users will have already installed these wretched DLLs on their system before they try the migration tool.
Previous versions of the migration tool installer were built by Pierre and he did have a Visual Studio license so could do the build and redistribute the software.
My experience and the time I wasted trying to find an answer to this question eventually turned up one discussion thread in which the complex issues that the team within Microsoft faces are exposed: see VC++ 2005 redistributable. Although this thread is a little old now the replies from Nikola Dudar are helpful in providing deeper insight into the issue and the conflict that having a chargeable development platform creates. On one hand Microsoft would like it to be easy for people to create software for their platform but they also have a paid-for development tool chain in Visual Studio. The existence of Visual Studio Express edition (a free lightweight development environment) appears to be suitable only for personal hobbyists and not for anyone wanting to build software for redistribution. There are lots of replies to the above article but if you search down for "release team" there is a reply that emphasises the difficulty of finding the balance between paid and express editions and a link to a blog post relating to the creation of the free to download redistributable packages. I like these types of forum discussions as they show that even 'evil empires' like Microsoft are full of ordinary people just trying to do their jobs.
The migration tool is written in python and uses the py2exe tool to convert the Python script into a set of binaries that can be distributed to other Windows systems as a ready-to-run application without requiring Python (and various other packages, including wxPython: used for the GUI) to be installed first.
The output of py2exe is a folder containing the executable and all its supporting files ready to package up. Originally this was all done by Pierre, my co-chair of the QTI working group. I'm happy to report that updating the installation scripts went fine and I've been able to create a new Windows Installer using InnoSetup.
There is a recipe for using py2exe with wxPython published on pythonlibrary.org called "A py2exe tutorial". However, I did have one problem with this recipe - I too had trouble with MSVCP90.dll but I needed the help of stackoverflow (thread: py2exe fails to generate an executable) to actually get the build going. Once done, I was concerned with the warning messages about the need to have a license to redistribute the DLL in my installer. I found another blog post on distributing python apps for the windows platform which spelt out my options. As I don't personally own a Visual Studio license it seems like I need to use the redistributable package which can be downloaded from Microsoft.
Unfortunately, when I download this file the license in the resulting installer does not appear compatible with packaging it into my installer for distribution with my tool.
Several people on the net seem to suggest that the DLL is off-limits but the 'redistributable' does exactly what it says on the tin. Indeed, if you don't run the package it isn't clear what license you signed up to by downloading it but once you run the installer it clearly says that "You may make one backup copy of the software. You may use it only to reinstall the software." and that you may not "publish the software for others to copy". So I've played safe and am crossing my fingers that my users will have already installed these wretched DLLs on their system before they try the migration tool.
Previous versions of the migration tool installer were built by Pierre and he did have a Visual Studio license so could do the build and redistribute the software.
My experience and the time I wasted trying to find an answer to this question eventually turned up one discussion thread in which the complex issues that the team within Microsoft faces are exposed: see VC++ 2005 redistributable. Although this thread is a little old now the replies from Nikola Dudar are helpful in providing deeper insight into the issue and the conflict that having a chargeable development platform creates. On one hand Microsoft would like it to be easy for people to create software for their platform but they also have a paid-for development tool chain in Visual Studio. The existence of Visual Studio Express edition (a free lightweight development environment) appears to be suitable only for personal hobbyists and not for anyone wanting to build software for redistribution. There are lots of replies to the above article but if you search down for "release team" there is a reply that emphasises the difficulty of finding the balance between paid and express editions and a link to a blog post relating to the creation of the free to download redistributable packages. I like these types of forum discussions as they show that even 'evil empires' like Microsoft are full of ordinary people just trying to do their jobs.
2011-06-17
Getting ready for HTML5: Accessibility in QTI, img and alt text
Last night I was playing around with David McKain and co's excellent MathAssessEngine site.
I tripped over an interesting error with some test data produced by the QTI migration tool. I was converting a basic MCQ with four images used as the choices. On loading my content package into MathAssessEngine I got four errors like this:
Error: Required attribute is not defined: alt
I went off in search of a bug in my XML generation code from the migration tool but discovered that what MathAssessEngine is really complaining about is an empty string being used as the alt text for an image. Actually, empty alt text is allowed by the specification (my QTI v2 files validate) and it is also allowed by HTML4 so I think it is more a bug in the MathAssessEngine, but it did force me to go and check current thinking on this issue because it is so important for accessibility.
According to the current editor's draft of HTML5 the alt attribute "must be specified and its value must not be empty" so it looks like QTI-based tools will need to address this issue in the near future.
The problem with the QTI migration tool is that it only has old scrappy content to work with. There isn't even the facility to put an alt attribute on QTI version 1.x's matimage which, incidentally, is another reason why the community should be moving to QTI version 2.
So is there any way to set the alt text automatically when migrating version 1 content?
One possibility is to use the label attribute on matimage as the alt text for the img element when converting to version 2. The description of the label attribute in QTI version 1 is a 'content label' used for editing and searching. This might be quite close to the purpose of alt for matimage because a text string used to find an image in a search might be a sensible string for use when the image cannot be displayed. However, editing sounds like something only the author would do so there is a risk that the label would be inappropriate for the candidate. There is always the risk of spoiling the question, for example, if the label on an image contained the word "correct" then candidates that experienced the alt text instead of the image would be at a significant advantage!
Another common way to auto-generate alt text is to use the file name of the image, this is less likely to leak information as authors are more likely to figure that the file name might be visible to the candidate anyway. Unfortunately, image file names are typically meaningless so it would be text for the sake of it and it might even confuse the candidate - especially if the names contained letters or numbers that might get confused with the controls: just imagine a speech interface reading a shuffled MCQ: "option A image B; option B image C; option C image A" - now our poor alt text user is at a serious disadvantage.
Finally, adding a general word like 'image' is perhaps the safest thing and something I might experiment with in the future for the QTI Migration tool but clearly the word 'image' needs to be localized to the language used in the context of the image tag, otherwise it might also be distracting. I don't have a suitable look-up table to hand.
So in conclusion, content converted from version 1 is always likely to need review for accessibility. Also, my experience with the migration tool reaffirms my belief that developers of QTI 2 authoring tools should start enforcing the non-empty constraint on alt for compatibility now to get ready for HTML5.
I tripped over an interesting error with some test data produced by the QTI migration tool. I was converting a basic MCQ with four images used as the choices. On loading my content package into MathAssessEngine I got four errors like this:
Error: Required attribute is not defined: alt
I went off in search of a bug in my XML generation code from the migration tool but discovered that what MathAssessEngine is really complaining about is an empty string being used as the alt text for an image. Actually, empty alt text is allowed by the specification (my QTI v2 files validate) and it is also allowed by HTML4 so I think it is more a bug in the MathAssessEngine, but it did force me to go and check current thinking on this issue because it is so important for accessibility.
According to the current editor's draft of HTML5 the alt attribute "must be specified and its value must not be empty" so it looks like QTI-based tools will need to address this issue in the near future.
The problem with the QTI migration tool is that it only has old scrappy content to work with. There isn't even the facility to put an alt attribute on QTI version 1.x's matimage which, incidentally, is another reason why the community should be moving to QTI version 2.
So is there any way to set the alt text automatically when migrating version 1 content?
One possibility is to use the label attribute on matimage as the alt text for the img element when converting to version 2. The description of the label attribute in QTI version 1 is a 'content label' used for editing and searching. This might be quite close to the purpose of alt for matimage because a text string used to find an image in a search might be a sensible string for use when the image cannot be displayed. However, editing sounds like something only the author would do so there is a risk that the label would be inappropriate for the candidate. There is always the risk of spoiling the question, for example, if the label on an image contained the word "correct" then candidates that experienced the alt text instead of the image would be at a significant advantage!
Another common way to auto-generate alt text is to use the file name of the image, this is less likely to leak information as authors are more likely to figure that the file name might be visible to the candidate anyway. Unfortunately, image file names are typically meaningless so it would be text for the sake of it and it might even confuse the candidate - especially if the names contained letters or numbers that might get confused with the controls: just imagine a speech interface reading a shuffled MCQ: "option A image B; option B image C; option C image A" - now our poor alt text user is at a serious disadvantage.
Finally, adding a general word like 'image' is perhaps the safest thing and something I might experiment with in the future for the QTI Migration tool but clearly the word 'image' needs to be localized to the language used in the context of the image tag, otherwise it might also be distracting. I don't have a suitable look-up table to hand.
So in conclusion, content converted from version 1 is always likely to need review for accessibility. Also, my experience with the migration tool reaffirms my belief that developers of QTI 2 authoring tools should start enforcing the non-empty constraint on alt for compatibility now to get ready for HTML5.
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