"Die Frau sieht das Kind."
Grammatically that would not be wrong since die Frau could be accusative and das Kind could be nominative instead of the other way around, but it would be very awkward to say or write something like that since it would be misunderstood 100% of the time if no further context was given.
Thank you for your explanation. I have been curious about this for some time now.
I'm learning Esperanto, which does not allow for this kind of confusion no matter in which order the words are put. HOWEVER. I gather from your answer that it's not that complicated in German either because common sense (no reference to Ehsan) would tell us that since both nouns can be exchanged grammatically (in this sentence), the sentence should be taken just as it sounds.
Really, in my perhaps awkward way, I am saying you have helped turn on a light bulb for me. Thank you.