I think it probably has to do with the successful communication of genetic information from one generation to the next, that is also capable of adapting to environmental changes. By that standard, I suppose one could write a computer virus that is also "alive."
Being unsophisticated in matters scientific, what you say sounds reasonable to me. So far, I think, this discussion has principally illustrated that, despite how much we know, we can't even describe (define) life in an adequate fashion.