Which of the following examples is grammatically correct?
There was someone at the door. It WOULD BE the milkman.
There was someone at the door. It WOULD HAVE BEEN the milkman.
If both are possible, do they mean the same thing?
Thank you very much for your kind help.
Paolo
If you hear someone knocking at the door, you can say: That will be the milkman. This is a function of will that Swan (Practical English Usage, p600) describes as "expressing certainty or confidence about present or future situations".
The same applies to past situations. If you told your wife that you were in the shower earlier in the day when you heard someone at the door, she could reply:
That would have been the milkman.
In other words: I am pretty sure (or certain) that it was the milkman.
You could also retain the will in such a context: That will have been the milkman. And possibly even: That would be the milkman. But I see no conditionality in such a response.
Neither, assuming your examples are complete.
There was someone at the door. It was the milkman.
works
The past tense makes it hard to guess your context
If you use "is", it makes more sense if you are informing someone about the fact
"There is someone at the door. It could be the milkman" (if you are not sure).
or
"There is someone at the door. It should be the milkman" (if you expect him).
depending on what you meant to say.
Your sentences could be fixed if you add a condition
There was someone at the door. It WOULD BE the milkman by the sound of the clinking bottles.
There was someone at the door. It WOULD HAVE BEEN the milkman, had he not broken his leg the day before.
If the person is alerting the fact that there is someone at the door now and they are expecting the milkman, then the sentence is as follows, where the "would" is used to show you expectations
"There is someone at the door; that would be the milkman."
