Passive or Active Voice?

[InChina10]

In the sentence, "Compared to Mary, Bill is tall." Is this in the Passive Voice structure?

I'm trying to help a friend do a corpus linguistics research project, and we can't seem to agree on this. I cannot determine how it could be passive voice without the verb "to be" present, nor could I discover any way to rewrite it into an active voice form.

I have checked grammar books, and cannot find any exact examples of this part of speech. Personally, I would write it as, "When compared with Mary, Bill is tall."

This paper requires analysis of Passive Voice structures written by L2 students, so I cannot change it but must determine if it is actually in passive voice format or not. Any help would be greatly appreciated.

[Alan]

Hi,

Your sentence is a contracted form of: 'If he is compared to Mary, Bill is tall' - which makes that a present passive. Consider also: 'If one compares him to Mary, Bill is tall' - which is the active form.

Alan
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[InChina10]

Thank you; that is a big help.