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Authoring free-text questions with extractors

This page discusses a free-text question with extractors.

Questions with a single extractor and multiple standard STACK inputs

This is a complex question which can be loaded from 

Doc-Examples/Specialist-Tools-Docs/Free-text-input/Free-text_with_extractors.xml

This page contains only notes, and we recommend you load this question and work through it.

Design

This question adds free-text working to a classic STACK question.

  • one input, the characteristic polynomial, is extracted automatically from the student's text.
  • students still have to fill in the final answer, as would be the case with a classic STACK question.

This combination is a pragmatic middle ground between trying to extract all answers with regex, and having students fill in forms.

Syntax hint as castext

To pre-fill in the "syntax hint" in the free-text input you need to do two things.

First create a maxima variable as a castext string

sh1:castext("
`
M = {#args(M)#}
`

-----------

Characteristic polynomial =

-----------
");

This contains

  1. the matrix in the question, but by using args(M) we get AsciiMath form M = [[8,-6,9],[12,-10,12],[0,0,-1]] rather than maxima syntax M = matrix([8,-6,9],[12,-10,12],[0,0,-1]). Note how we use castext within Maxima here, and we embed variables with the {#...#} form, so they are without LaTeX symbols.
  2. the syntax hint contains the prompt for students to ensure the regex has a reasonable target: Characteristic polynomial =
  3. the input ans1 has syntax hint as castext {#sh1#} which displays the castext without "s, but maintaining the linebreaks.

Extractor

Note the ASCII block has an extractor 

[[input:ans1]] [[validation:ans1]]
[[ascii input="ans1"]]
  [[extractor type="regexmatch" targetinput="scp" regex="^\\s*Characteristic polynomial\\s*=\\s*" /]]
[[/ascii]]

This fills in one of the inputs, scp which is the student's characteristic polynomial. This input has very relaxed stars (basically insert *s etc).

This input is not displayed, note

<p style="display:none">[[input:scp]]</p>

but the validation tag will be visible if students make a syntax error.

Teacher's answer

The teacher's answer for ans1 is also written as castext within Maxima, in a very similar style to the syntax hint.

Questions with a multiple extractors and multiple standard STACK inputs

This is a complex question which can be loaded from 

Doc-Examples/Specialist-Tools-Docs/Free-text-input/Free-text_with_multiple_extractors.xml

This page contains only notes, and we recommend you load this question and work through it.

Design

This question extracts two independent answers, and from the student's working. Students still have to fill in the final answer, as would be the case with a classic STACK question.

This combination is a pragmatic middle ground between trying to extract all answers with regex, and having students fill in forms.

Extractors

This is the complete question text:

<p>You have a parabola of the form \(f(x)=a\,x^2+b\) which satisfies \(f({@x1@})={@f1@}\) and \(f'({@x2@})={@f2@}\).</p>
<p>Work line by line below, find the values of \(a\) and \(b\) and hence the formula for \(f\).  Justifying your answer fully.</p>
<div class="free-text-container">
[[input:ans1]] [[validation:ans1]]
[[ascii input="ans1"]]
  [[extractor type="laststringremainderwhitespace" targetinput="saa" search="a =" /]]
  [[extractor type="laststringremainderwhitespace" targetinput="sab" search="b =" /]]
[[/ascii]]
</div>
<p>Make sure your answer contains lines <code>a=?</code> and <code>b=?</code> for your values of the coefficients.</p>
<p style="display:none">[[input:saa]]</p>
<p>\(a=\)[[validation:saa]]</p>
<p style="display:none">[[input:sab]]</p>
<p>\(b=\)[[validation:sab]]</p>
<p>\(f(x)=\) [[input:saf]][[validation:saf]]</p>

Notes.

  1. The inputs saa and sab are hidden with <p style="display:none">, however validation information is available via compact validation so students can see their answers are correctly extracted.
  2. Note the use of the laststringremainderwhitespace extractor, with a simpler search term, rather than a regular expression.
  3. Students still have to fill in the final answer, as would be the case with a classic STACK question. This could be extracted automatically with a further extractor block within the ascii block in the question text.
  4. The input and [[ascii]] block are contained in the <div class="free-text-container"> so they appear side by side.

In this example the PRT is minimal, and could be improved for partial credit.