Eat_On_Time ? Theme 3.3 Planning for Linguistic Variation Sentences generated by Picture Books vary in length and word complexity according to the user ? s age . The variation in length is handled by specificity character goals ( SCG ) that are ap-pended as supporting details to their respective character goals . SCGs are designed so that their existence will give more detail to the preceding character goal while ensuring consistency , and that their non-existence will still make the story complete .