Practical Grammar 3

Features

The lexical entries in Grammar 1 all looked like the following:

this D;
those D;
bottle N;
bottles N;

Together with the rule

NP -> D N;

the grammar accepts all the following strings as grammatical:

(1) this bottle
(2) *those bottle
(3) those bottles
(4) *those bottle

In this unit, we will change the grammar so that it makes the correct predictions about (1)-(4).

The source of the problem pointed out above is easy to spot: English determiners and nouns can both be singular or plural and in an NP of the form 'D N' the two words have to agree in number: either they are both singular or both plural. This is shown by (1)-(4).

What this shows, is that so far, the grammar does not contain enough information about words. Besides a part of speech, words also have inflectional features and the values of these features are regulated in the syntax (this is why these features are also called morphosyntactic features: they determine the morphological shape of words, but there distribution is determined by the syntax).

Features

So, let us add features to words. First, some terminology. We make a distinction between a feature and its value(s). This is illustrated for nouns and determiners below:

1. Nouns and determiners carry the features PER(son) and NUM(ber).
2. The possible values of the feature PER are: 1, 2, 3.
3. The possible values of the feature NUM are: sg, pl.

With these concepts, we can add features to the words in (1)-(4) which will lead to the correct predictions for these sentences by our grammar.

Exercise 1

• Change the lexical entry of the word this exactly as is shown below:

this D
     [PER:3,
      NUM:sg];

• Save the grammar.
• Parse.

You will notice a difference from Grammar 1. When you parsed a string in the previous grammar, xlfg showed you one window per string which was labeled 'Constituent Structure'. Now there is a second window which is labeled 'Functional Structure'. Unfortunately, that second window is empty. So, where is the inflectional information that we added to the word this?

• Click on the D node in the Constituent Structure.

Ahh! Now the D node has a colored block around it and simultaneously the Functional Structure shows the features PER and NUM and their values we added for the word this earlier.

What we are seeing here for the first time is that the grammar associates two different kinds of information with words (and also phrases, as we will soon see):

C(onstituent)-structure information consists of the syntactic category (= parts of speech) of an expression in a phrase structure tree.

F(unctional)-structure information consists of features and values that express the functions of an expression.

Exercise 2

• Add PER and NUM features (and their correspondig values) to the three other words in the lexicon.
• Save.
• Parse.
• Click on the D or N node in Constituent Structure to display the f-structure information associated with that node in Functional Structure.

Exercise 3

• Display the Constituent Structure of those bottle.
• Click on the D and the N node to display their f-structures.
• They differ, as expected.
• Yet, the grammar does not mark the string as ungrammatical! Think about why that is! Determiners and nouns are supposed to agree in PER and NUM. Here, they don't agree in NUM and yet the grammar does not seem to mind. Again, why?

The answer is the following: you know that determiners and nouns agree in English, but the grammar doesn't know! Why? Because you haven't told it!

You are the grammar writer and the grammar only contains the information that you have given it!

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