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CSC 363            Homework Exercise 1 -- Marking Scheme          Fall 2008
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NOTE TO STUDENTS:

You will find below the marking scheme used for your homework, including
the meaning of marking codes and number of marks associated with each one.
This file also contains my instructions to the marker (so you can get an
idea of how the homework was marked) and the marker's comments about each
question.

Please take the time to read this carefully before you ask questions about
the grading of your homework.


NOTE TO MARKER:

Be picky!  On any homework, it is the responsibility of students to show
that they understand how to solve each problem and to write up their
answers carefully.  At the same time, keep in mind that exercises are worth
only 1.5% of the final grade, so your marking should be somewhat coarse.
And remember that marking is not just about evaluating the students's
performances, but also about giving them feedback so that they can learn
from their mistakes.  This is especially important for students who made
numerous or more serious mistakes, as they are likely to need more feedback
in order to understand why their answers were incorrect.

For each question, I list solution elements with an associated code for
writing on student papers (the letter(s) between underscores _) and a
number of marks.  There are also general errors (with associated codes)
given below, with a maximum number of marks to take off for each type of
general error (as a percentage of the value of the question).  You will
likely encounter other common errors, or maybe decide to break down the
marking scheme further.  Simply make note of these changes/additions to
the marking scheme, and introduce new code letters (or short words) to
allow you to quickly give accurate feedback to the students (both in terms
of what they did wrong and how many marks it cost them).


GENERAL ERRORS (marked negatively, in addition to any other errors):

    _N_otation [up to 20%]:  incorrect/ambiguous notation

    _V_agueness [up to 20%]:  incorrect/unjustified/vague claim


1.  [4 marks]

    _E_rror [up to 4 marks, using negative marking]:  take off 1 mark for
        each error in the tracing, over all parts (take off the mark only
        the first time that each error is made, i.e., if an error is made
        multiple times, don't take off 1 mark each time)

    Following the General Errors above, take off up to 1 additional mark
    overall for unintelligible notation -- if a student did not use the
    exact notation used in lectures and the textbook, their notation should
    at least be straightforward (or it should be explained).

    Marker's Comments:  I used the following additional codes.

    L1:  Wrong configuration.  Check again the table of the transition
        function.

    L2:  Incorrect or ambiguous use of notation.


2.  [11 marks]

    _H_igh-level [1 mark]:  correct high-level idea for the computation

    _I_mplementation-level [5 marks]:  clear, correct implementation-level
        description -- including handling "roll-over" (when the input is a
        string of 2's)

    _F_ormal-level [5 marks]:  clear, correct formal-level description,
        including the format of the transition table/diagram and the
        presence of comments to relate it to the implementation-level
        description

    Marker's Comments:  I used the following additional codes.

    L3:  Failed to handle the roll-over case (see sample solutions).

    L4:  Missing formal description of the TM, that is the set of states,
        input and output alphabets.

    L5:  There are no comments relating the implementation level
        description with the formal level description.

    L6:  Failed to meet the output requirement, as described by the
        question.  Output string has to start with a blank "cell".

    L7:  Wrong TM.  See input examples in your paper.  I encourage you to
        run your TM in these instances.


3.  [3 marks]

    Be especially picky for this one, as it is a bonus!

    _L_anguage [2 marks]:  correct language

    _J_ustification [1 mark]:  reasonable justification

    Marker's Comments:  I used the following additional codes.

    L8:  Not sufficient justification.