Pattern-match question type
Pattern-match questions allow the student to give an answer of up to about 20 words, which can then be automatically graded by matching the students response against a number of different patterns expressed in the PMatch syntax. The first matching pattern determines the score and the feedback.
This is a question type created and maintained by the Open University.
More documentation is available in the Open University's reference manual. That includes a description of the pmatch syntax. There is another page that explains The OU PMatch algorithm, but that was written before development started, and may not be a 100% accurate description of what was finally implemented.