A typical natural language production rule looks like this:

S => NP VP

for a declarative language, or

S => aux NP VP

for a question.

S = sentence, NP = noun phrase, VP = verb phrase, aux = auxiliary.

In this case aux is rewritten by a single word: did, can, or will. When I tried to parse more complicated sentences I stumbled over the fact that the aux part was not a simple part-of-speech, but rather a phrase on its own; it can consist of multiple words.

Be careful when using this table: I am not a language specialist. Just a programmer. Although I tried very hard not to make mistakes, some combinations of grammatical categories seemed far fetched (i.e. "John used to be being bitten by a dog") and I had to use Google to find out if such a combination is being used at all. And even though I didn't add sentences I could not find via Google, some of them were very rare and may have been errors by the users of the language.

Legend

For each color used, I give an example and the meaning of the word group.

bites = simple present (verb form)
biting = present participle (verb form)
bitten = past participle (verb form)
bite = infinitive (verb form)
could = modal auxilliary
is going to = primary auxiliary (italic = modify for tense, person, number)

Verb forms

A verb has different forms, and these are important with respect to these sentences.
Possible values: simple present, simple past, present participle, past participle, infinitive
Reference: Participle - Chomp chomp, Word forms (simple, participle, infinitive) - English Club

Grammatical categories

The auxiliaries in the table have been grouped by grammatical category combination. Some of these categories were new to me too, so it is probably a good idea that I explain them. And while I'm at it, I may as well name the link with their semantic counterparts.

Mood

The mood of a sentence is the main structure, and is represented by a production rule with S at the left hand.
Typical values: declarative (statement), interrogative (question), imperative (demand)
Meaning: the mood determines the speakers attitude toward that what they are saying.
Reference: Grammatical mood - Wikipedia

Voice

In which position do we find the agent of the sentence? In the subject position (active) or in the direct object position (passive)
Typical values: passive, active
Meaning: the subject position determines the focus of the sentence
Reference: Grammatical voice - Wikipedia, Examples of active and passive voice - Helping hands

Tense

When did the event or state in the sentence occur? Or: temporally when.
Typical values: past, present and future
Meaning: tense determines the time of the event, relative to the present moment
Reference: Grammatical tense - Wikipedia, Perfect tense - Wikipedia

Aspect

The the internal temporal constituency of a situation. Or: temporally how.
Typical values: simple (happens now, "a dog bites john"), progressive (ongoing: "a dog is biting John"), perfect (completed event, "a dog has bitten John"), habitual (customary, "a dog used to bit John"), prospective (future, "a dog is going to bite")
Meaning: aspect is a specification of the tense aspect, and determines the period of time within the range specified by tense
Reference: Grammatical aspect - Wikipedia

Modality

The proposition the speaker wishes to make with respect to the
Typical values: can, will, must
Meaning: will specifies that the event takes place in the future, can specifies that the event is possible, not certain, must specifies that the event is required.
Reference: Linguistic modality - Wikipedia

Conclusive remarks

When creating production rules, remember that these sentences may need to be negated as well ("John may not have been bitten by a dog"). Further, in the examples I have only used the present tense, using the third person, in the singular. An example of a first person, plural (a dog => we), past tense (bites => bit) sentence would be:

We bit John

I formatted all words that need to change to account for these three grammatical categories in italic.

Links

• Auxilliary verb - Chomp chomp
• Auxiliary verb - Wikipedia