1 - You way with using first subanswer was somewhat confusing for our teachers, so I try to find better solution. You may implement it too. Do you notice regex validation using this correct answer? Just try to save question without 100% grade regex matcing it.

2 - Let's consider you example with animals. The regex for correct answer would be something like (the|a)\s+[cbr]at . If you set Exact Matching to Yes, the answer must be strictly as you describe it, for example 'a rat' with nothing else in it (the way the ordinary teacher would expect it to work). If you set it to No, the regex will match any string which contains correct answer, for example 'this is a rat maybe'. In No mode you still can specify exact matching for some options using regexp syntax, that is enclosing it in ^$ i.e. ^(the|a)\s+[cbr]at$ (Exact Match Yes just do it to every regex). You may want to catch correct answers with exact matches and parts of incorrect as partial, for example ^an\s+ would catch wrong article at the start of the string, and you can tell the student whats wrong. In that case it is easy to use an\s+[cbr]at with Exact Matching, but in more complicated cases this isn't so easy.
Can you think how I should to clarify it in help? I'm so familiar with regexes that may omit something important to newbies.

3 - A dog maybe I can't properly understand you needs. Do you want to catch partially wrong answer such as 'bat' without either 'a' or 'the'? I would set Exact Matching to No, create first regex ^{(the|a)\s+[cbr]at$ for 100% and something like [cbr]at for a lesser grade on the second, than you catch any phrase containig cat, bat or rat except the correct ones (the questions in Moodle now thought that first matching response gives grade). This, hovewer, will catch 'catalogue' as it contains 'cat'. You can upgrade it to (}|\s+)[cbr]at(\s+|$) to catch a word cat/bat/rat, enclosed in spaces or start/end of the string. If you want to catch phrase that must end with cat, bat or rat with at least one space before the word (except correct) then you can write \s+[cbr]at$ instead. To create a more specific regex I must know exactly what you want - i.e. which cases must be caught and which must not.

Also, you (as, I think, many contributors there) may like to vote for MDLSITE-551. Please see MDL-14899 too, you may like the block.

1- I said I agreed that yours was a good idea. Yes, I noticed how regex validation used that correct answer. And I will see if I can incorporate this idea into my REGEXP question type. Thanks.

2- OK, now I understand better what you want to achieve with the "Exact Matching Yes/No" setting. Thanks for the examples.

3- "I can't properly understand you needs. Do you want to catch partially wrong answer such as 'bat' without either 'a' or 'the'?"
Not exactly. I want to catch the ABSENCE of mandatory words in the student's answer. Here are some examples of the way I do it in my REGEXP plugin.
a) regular expression --(the|a)\s.*
student's response "cat" or "dog" or "tulip" or ... any character string not beginning with "the " or "a "
feedback message : "You are missing an article at the beginning of your answer"
b) question what are the colors of the French flag?
regular expression to catch ABSENT "blue" color : --(^|.\b)blue\b.
student's response: "red and white" or "it's red, yellow and white" or ... any response not beginning with "blue" or containing the word "blue"
feedback message: "You are missing the color BLUE"
I don't think you can catch these "missing mandatory" words just by using regular expressions, this is why I added the – syntax to my REGEXP plugin. But maybe you can suggest something. Of course, I agree that the problem is that I am introducing a special syntax which is not part of the standard regular expressions syntax; but I do it because I need it for my didactic purposes...

Joseph

3 Well, you can catch abscence of something using the way regexes are compared in Moodle in two steps:
a) first regex must catch any correct answer
b) second regex must contains .* instead of missing fragment - it will catch what you want

for the articles if you don't interested in anything except the article:
a) (the|a)\b.*
b).*
Let's recall you cat/bat/rat example. then
a) (the|a)\s+[cbr]at
b) .*\s+[cbr]at catching missing article
you can write also
c) (the|a)\s+.* to catch anything wrong about an animal

Actually, you'll need more options that Tim mentioned in his last comment to MDL-16344 (go see this Bugzilla page) than regexes. Can we work on implementing it together? You'll get quite pains trying to catch with regexes blue, red and yellow in any possible order.

Oleg, I recently realised that you can do blue, red and yellow in any possible order using regexes, and without listing all six possible orders, but you have to use assertions Something like

^(?=.\bblue\b)(?=.\bred\b).\byellow\b.$

but that is hardly intuitive! (And I don't know what sort of performance you get out of the preg engine with expressions like that.)

http://docs.moodle.org/en/Development:Shortanswer_question_development

Please, add description of features you need in ' initial types of the rules' list. Keep in mind that you can place negation before any rule, so you "absence some words" is already there.

"Please do not hesitate to let me know if there is anything I can do to be of assistance or if you have any questions. " - actually I would like you assistance (if you can) in another contrib matter. Some time later I write for our university block that just display a link for MyMoodle page. Our students found it very useful (forcing everyony to MyMoodle on login irritates experienced users, especially staff), so I release it there. The block is so simple and generally useful, that it probably would be better in the core, than there. I created MDL-14899 for this (we even get some votes). Eloy add +1 and reassigned to Martin for final consideration, but Martin appears to be quite busy. Could you please ensure that this matter wouldn't be forgetted and would be resolved somehow: either inclusion in the core or, failing that, move it there?

Best regards, - Oleg.

http://docs.moodle.org/en/CVS_(developer

http://docs.moodle.org/en/Eclipse

I'll add myself as a watcher to MDL-14899. If you feel that the issue has stalled, just add a comment. My experience is that we do pretty well at keeping things moving along and resolving issues. From what you say, it sounds like a good idea that there is a way to access their My Moodle page. I'll review the issue and comment there.

Peace - Anthony