What are the terms for the parts of a comparative?

If I am comparing "thee" to "a summer's day", in other words comparing for equality a == b

What are the proper terms that relate to a and b?
I'd call == the comparator, maybe a the subject.. b the object?

I looked here and they only mention 'entities' http://en.wikipedia.org/wiki/Comparative

The Oxford Dictionary of English Grammar (p77) has this extract in its entry on comparison:

In comparative clauses introduced by than or as, whatever is represented by the adjective, adverb etc. that functions as the comparative element is sometimes called the standard of comparison, and the basis of comparison is whoever or whatever is being compared in the comparative clause, Thus in Pete is happier than Paul, the standard of comparison is happiness and the basis of comparison is Paul.

If we rewrite Shakespeare's famous line as:

You are more beautiful than a summer's day

then the standard of comparison is beauty and the basis of comparison is a summer's day. And you could say that you is the subject of the comparison.

How about "tenor" and "vehicle"?

In my literature class, these are the terms we use when describing the objects in a metaphor, where the "tenor" refers to the object being described and the "vehicle" refers to the image that carries "the weight of comparison," that to which you are comparing the tenor.

In your example, "thee" would be the tenor, and "a summer's day" the vehicle.

Here is an excerpt from Encyclopedia Britannica:

Tenor and vehicle, the components of a metaphor, with the tenor referring to the concept, object, or person meant, and the vehicle being the image that carries the weight of the comparison. The words were first used in this sense by the critic I.A. Richards.

http://www.britannica.com/EBchecked/topic/587448/tenor-and-vehicle