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QTI Components

Authoring response processing

Response processing is what turns a candidate’s answer into a score. It’s declarative: you write a small tree of rule and expression elements inside <qti-response-processing>, and the library walks that tree and executes it whenever something calls processResponse() on the item.

The fast path: built-in templates

Most items don’t need custom rules at all. QTI defines a handful of standard response-processing templates, and <qti-response-processing> recognizes them by URL — this is what the Quick Start’s example item actually uses:

<qti-response-processing template="https://purl.imsglobal.org/spec/qti/v3p0/rptemplates/match_correct.xml" />
TemplateScoring
match_correct1 point if the response exactly matches the declared correct response, 0 otherwise.
map_responseLooks up the response in the response variable’s qti-mapping (per-choice point values).
map_response_pointSame idea, for point-based interactions (e.g. Select Point), via qti-area-mapping.

No network fetch happens for these — the library recognizes the template by its filename and expands it locally.

What match_correct actually expands to

Seeing the real markup is the fastest way to understand the rule model, so here’s exactly what that one-line shortcut expands to internally:

<qti-response-processing>
  <qti-response-condition>
    <qti-response-if>
      <qti-match>
        <qti-variable identifier="RESPONSE"></qti-variable>
        <qti-correct identifier="RESPONSE"></qti-correct>
      </qti-match>
      <qti-set-outcome-value identifier="SCORE">
        <qti-base-value base-type="float">1</qti-base-value>
      </qti-set-outcome-value>
    </qti-response-if>
    <qti-response-else>
      <qti-set-outcome-value identifier="SCORE">
        <qti-base-value base-type="float">0</qti-base-value>
      </qti-set-outcome-value>
    </qti-response-else>
  </qti-response-condition>
</qti-response-processing>

Reading it as an execution model rather than markup:

  1. <qti-response-processing> runs each of its child rules in order — normally just one <qti-response-condition>.
  2. <qti-response-condition> evaluates its <qti-response-if>/<qti-response-else-if>/<qti-response-else> children in order, and runs the sub-rules of the first one whose own expression evaluates to true.
  3. <qti-match> is a boolean expression — it compares its two child expressions for equality. Here that’s <qti-variable identifier="RESPONSE"> (the candidate’s answer) against <qti-correct identifier="RESPONSE"> (the answer declared in <qti-response-declaration>’s <qti-correct-response>).
  4. <qti-set-outcome-value identifier="SCORE"> assigns the outcome variable named SCORE to whatever its child expression evaluates to — here, a literal <qti-base-value base-type="float">.

Writing this out by hand instead of using the template shortcut is exactly how you’d handle anything the standard templates don’t cover — partial credit, multiple conditions, combining several interactions’ responses into one score, and so on.

Live example

This item uses the exact rule tree above, written out explicitly rather than via the template shortcut. Pick an answer and press Submit to actually run it:

Common operators

Response processing has a full expression vocabulary beyond qti-match — around 35 operators in @qti-components/processing, covering logic, comparison, math, and container manipulation. Rather than a page per operator, here’s the full list at a glance; each links conceptually to the QTI 3.0 operators spec for exact semantics:

Logic — qti-and, qti-or, qti-not, qti-any-n (true if between N and M sub-expressions are true)

Comparison — qti-match, qti-equal, qti-equal-rounded, qti-gt/qti-gte, qti-lt/qti-lte, qti-duration-lt/qti-duration-gte, qti-pattern-match, qti-substring, qti-is-null, qti-null

Math — qti-sum, qti-product, qti-subtract, qti-divide, qti-integer-divide, qti-integer-modulus, qti-power, qti-round, qti-round-to, qti-truncate, qti-gcd, qti-min/qti-max, qti-integer-to-float, qti-math-operator, qti-stats-operator

Containers & lookups — qti-index, qti-field-value, qti-container-size, qti-delete, qti-repeat, qti-random-integer, qti-map-response, qti-map-response-point, qti-correct, qti-default

Variables — qti-variable (read any declared variable by identifier), qti-base-value (a literal value)

See also