Assignment 1 grading and comments

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Problem 1

30 marks, 10 per item

People generally did very well on that, except that some has forgotten that the question requested that you indicate at which step each item is added to the chart by numbering the arcs.

Problem 2

Grads 17, Undergrads 15 marks, 5 marks per item, grads-only question 2 marks

People did well on that, too. The most common mistake was in (c). People tried to draw the RTN which would allow
 NP -> Det N PPS 
combination rather than
 NP -> Det N 
.

Problem 3

15 marks

People did reasonably well at that, though in a few cases they didn't seem to have tested the grammar properly. Note that calling (show-answers) will give you a final parse tree.

One of the typical problems here was getting a grammar that would build the trees for sentences, but not the correct ones. There were different cases, for example, the rule

  NP => NP PP
  
The rule is correct to analyze sentences like "He saw a boy with red hair", but it will result in the analysis
  [S [NP He] [VP saw [NP the man] [VP saw [NP [NP the wood] [PP with a saw]]]]]
  
This get us very strange interpretation: "he saw someone sawing the wood which had a saw in it" or something like that, which is certainly not what we want to get. There may be multiple trees corresponding to the same sentence, but if you're asked to write a grammar that accounts for it, it should be able to produce only correct interpretations.

Another problem was that many people missed the clause "justify your grammar with examples". It is usually important to show that your grammar allows only correct analyses and disallows ungrammatical utterances, as well as that it can handle a range of sentences rather then some very specific type. I didn't penalize heavily for that this time if there were at least some examples provided, but this argument must be present in your future assignments. You can see my standard answers for what can be a reasonable example.

Problem 4

Grads 18, Undergrads 10 marks, a - 10, b - 15 (part a) + 3(part b)

The biggest problem for people here was to come up with a good grammar. Again, it is reasonably easy to write a grammar that will account for all different cases, but it isn't enough. While it is impossible to achieve full generality, your grammar should be as general as possible and have other features described in NLU section 3.2. Therefore it is unreasonable, for example, to introduce a special feature value for "you" - this looses generality and explanatory power of the grammar by introducing an additional special case which in reality can be handled by just specifying that both subject and object case for the 2nd person pronoun have the same form.

For grads only part, some people didn't notice that problem 4 in NLU had questions (a) and (b) and answered only 1 of them.

Statistics

Here are the scores so that you can compare your performance to others.

(Grads max 90, Undergrads max 60)

           50.00
           51.00
           65.00
           70.00
           89.00