non-additive facts in a fact table?

I'm modelling an audio-conversion process where audio files are received and converted into text files.

I have a fact_conversions table, with each row describing a single audio conversion but the only facts in this fact table are audio_length (the length in seconds of the audio file) and conversion_time (the time in seconds it took to convert the audio into text).

Neither of these facts are additive across any dimension but users do want to know things like the average audio_length and the average_conversion time. In order to calculate the averages I'd need to add up the corresponding fact and divide this by the total number of conversions so does this calculation make them additive?

fact_conversions

date_received_key

date_converted_key

language_key

audio_length

conversion_time

How are they not additive across the dimensions? You could easily ask for the total audio-length of files in German converted during the first three months of last year.

Dave Jermy wrote:How are they not additive across the dimensions? You could easily ask for the total audio-length of files in German converted during the first three months of last year.

I see your point. Technically they are additive but I never looked at it in that way because the business would never be interested in total audio-length. But I guess just because the business aren't interested in it doesn't mean it's not additive.