# Q3a · Top-down restaurant parse

Subject: Natural Language Processing

Exam: TEE

Reader: https://deep-learning-study-room.vercel.app/nlp/#tee/papers/legacy-r24/q3a

Canonical: https://deep-learning-study-room.vercel.app/read/nlp/tee/papers/legacy-r24--q3a/

Previous examination · complete worked answers

**Question. Draw a top-down parse of “A restaurant serves dosas” using the printed grammar: S→NP VP | Aux NP VP | VP; NP→Pronoun | Proper-Noun | Det Nominal; Nominal→Noun | Nominal Noun | Nominal PP; VP→Verb | Verb NP | VP PP; PP→Prep NP. Lexicon: Det=A; Noun=restaurant,dosas; Verb=serves.** [10 marks]

### Answer

**As printed, this grammar cannot derive the complete sentence.** The object dosas is a Noun, but NP has no rule for a bare Nominal/Noun. NP→Det Nominal would require a determiner before dosas that is absent.

### Clearly stated minimal repair

Add NP→Nominal. The repaired top-down derivation is:

| Step | Sentential form |
| --- | --- |
| 1 | S |
| 2 | NP VP |
| 3 | Det Nominal VP |
| 4 | A Noun VP |
| 5 | A restaurant Verb NP |
| 6 | A restaurant serves Nominal |
| 7 | A restaurant serves Noun |
| 8 | A restaurant serves dosas |

SNPDetANominalNounrestaurantVPVerbservesNPNominalNoundosas

[S [NP [Det A] [Nominal [Noun restaurant]]] [VP [Verb serves] [NP [Nominal [Noun dosas]]]]]

This tree uses the added rule only for the object. Do not silently pretend it is derivable under the original rule set. Left-recursive Nominal/VP alternatives require a terminating parser strategy; the displayed successful derivation chooses the needed finite branches.

**Source / convention note.** Original CFG is incomplete for the given bare-plural object. Exact failure and explicit repaired derivation are both shown.