I have not been able to find a clear issue on omitting reviews from Microdata.

I understand that Microdata values for reviews will default to a certain number when omitted, but I was wondering if it would be correct/acceptable to completely omit the review node completely.

I can see where reviews and average "star" ratings would be of help to the end user, especially for things like recipes. However, what if there are no reviews for a product or application?

To be completely clear - let's isolate this question to only software applications or extensions. What if a particular piece of software or extension was not featured on an "app store" or other site that provided reviews? Wouldn't the formats still be helpful by providing version number, download URL, compatible software - etc?

Sorry for the lengthy background, but I just don't understand why it seems that reviews must be part of a Microdata markup. Or, am I wrong in this assumption?