Is a dream object an existent? How about the face in the mirror? The context for this question is contemporary Tibetan Buddhist Monastic debate and associated definitions as practiced at Sera Je Monastic University. I'm looking for answers according to the specific definitions and system of jargon used in that context.

In Tibetan Buddhist monastic debate according to The Course in Buddhist Reasoning and Debate an existent is defined as, "that which is realized by a valid cognizer."

I'm asking whether under such a definition a dream object - such as a snake - is considered an existent or a non-existent such as the son of a barren woman.

I believe that it must be considered an existent as it is known by a directly perceiving mental consciousness given the above context. The same can be said of a face in the mirror although in this case it is directly perceived by the eye consciousness. Is this true from viewpoint of above context? Is it true from the Prasangika viewpoint?

I posit that a dream snake and a snake I perceive in waking life are both conventionally existent. Further, that neither are ultimately existent. And that neither are real except from the perspective of a worldly consciousness. That is, they are both equally unreal. Is this true from the Prasangika viewpoint?

If not, please give reasons according to the context mentioned above.
A dream object is an existent, since it is apprehended by a conventional valid cognizer, that is a conventional cognizer that is not subject to any of the four superficial causes of error.

A dream object is a phenomena source. It is apprehended by mental consciousnesses (except in the continuum of a buddha).

According to Geshe Tenzin Tenphel, a dream consciousness is necessarily a non-conceptual perceiver, while Geshe Lobsang Jamphel says that a dream consciousness can be either non-conceptual or conceptual. Either way, a dream consciousness apprehending a dream car as a dream car is valid with regard to the entity of the object it apprehends.

The reflection of a face in the mirror is also an existent. Unlike the dream object, it is not a phenomena source but form.  While it is empty of being an actual face, it is not empty of being a reflection. It is in the entity of a reflection. A consciousness apprehending it as a reflection is valid with regard to the entity of the thing. On the other hand, a consciousness apprehending a mirage as actual water is wrong with regard to the entity of the thing, but that does not make the mirage a non-existent.

According to Prasangika-Madhyamika, conventional truths are not real. However, they are real in relation to the world in that, in the perspective of an ordinary being, they exist the way they appear. That is also why we say: of both truths (conventional and ultimate), only ultimate truths are actually truths. Conventional truths are only truths in relation to a consciousness that is wrong with regard to the mode of existence of phenomena.