relational algebra 3

Question 1

Universal quantification

Answer 1

this means that a condition whisch apply for all in other words !∃ (there is none)

Question 2

different condition which help one working on all

Answer 2

the negation of «for all»:
« ∀ item the condition is true »
is not «for none»:
« ∀ item the condition is false» <– no!
but it is:
«∃ an item for which the condition is false»