「どちら様でしたか？」 - why past form?


In a novel I'm reading (「キッチン」 by 吉本{よしもと}ばなな), there's this situation where
the door opens and a woman enters the room asking for the main character by
name. The main character, being surprised and not knowing the woman, asks her
who she is:

> 失礼ですが、どちら様 **でした** か？

My question is: why the past form of です is used in 「どちら様でしたか？」? Those two
people are standing there talking to each other, so why the past form? Would
it be possible to ask 「どちら様ですか？」?




It's used for politeness. Here's what Martin writes in his 1975 _Reference
Grammar of Japanese_ , p.603:

> **Sometimes the perfect is used more for politeness than for time
> reference** : あなたはどなたでした = お名前は何とおっしゃいましたか 'What did you say your name was?'
> ( **when the person has actually not yet said** ); 判子をお持ちでしたね 'You have your
> chop (= signature-seal) with you, I presume'.

Note that Martin refers to the 〜た form as the "perfect" rather than "past
tense" form. This usage of た with present time reference is usually only in
questions, as noted by Hasegawa in her paper [_Tense-Aspect Controversy
Revisited: the -ta and -ru forms in
Japanese_](http://hasegawa.berkeley.edu/Papers/Hasegawa99.pdf) (1999), which
was pointed out by Tim in the comments section.




It's used for politeness. Here's what Martin writes in his 1975 _Reference
Grammar of Japanese_ , p.603:

> **Sometimes the perfect is used more for politeness than for time
> reference** : あなたはどなたでした = お名前は何とおっしゃいましたか 'What did you say your name was?'
> ( **when the person has actually not yet said** ); 判子をお持ちでしたね 'You have your
> chop (= signature-seal) with you, I presume'.

Note that Martin refers to the 〜た form as the "perfect" rather than "past
tense" form. This usage of た with present time reference is usually only in
questions, as noted by Hasegawa in her paper [_Tense-Aspect Controversy
Revisited: the -ta and -ru forms in
Japanese_](http://hasegawa.berkeley.edu/Papers/Hasegawa99.pdf) (1999), which
was pointed out by Tim in the comments section.

