20. A computerized assessment grading method comprising: upon receipt of an encoded equation-based response to an assessment question, said assessment question comprising an equation, decoding, by a processing device, the encoded equation-based response and processing the decoded equation-based response to determine a hierarchy of operators and operands and a grading method selected from a plurality of different grading methods; determining, by the processing device, if the response comprises an equation that matches the equation of the assessment question; if the response does not comprises an equation that matches the equation of the assessment question, comparing, by the processing device, (i) the response hierarchy of operators and operands with (ii) a solution hierarchy of operators and operands; and grading, by the processing device, the response according to the determined grading method based on the comparison; wherein said grading comprises awarding a score based on the extent to which nodes of the syntax trees match.
20. A computerized assessment grading method comprising: upon receipt of an encoded equation-based response to an assessment question, said assessment question comprising an equation, decoding, by a processing device, the encoded equation-based response and processing the decoded equation-based response to determine a hierarchy of operators and operands and a grading method selected from a plurality of different grading methods; determining, by the processing device, if the response comprises an equation that matches the equation of the assessment question; if the response does not comprises an equation that matches the equation of the assessment question, comparing, by the processing device, (i) the response hierarchy of operators and operands with (ii) a solution hierarchy of operators and operands; and grading, by the processing device, the response according to the determined grading method based on the comparison; wherein said grading comprises awarding a score based on the extent to which nodes of the syntax trees match. 21. The method of claim 20 wherein said grading method is selected from Order Equivalence, Formal Equivalence and Content Equivalence grading methods.