expression
from the viewpoint of; according to
Used after a noun or clause to indicate a perspective, basis, or standard for judgment. Often translates as 'in terms of', 'based on', or 'judging from'.
法律の上では、それは違法だ。
From a legal standpoint, that is illegal.
理論の上では可能だが、実際には難しい。
It's possible in theory, but difficult in practice.