Definition
- For two soft sets (F , A) and (G , B) over a common universe U, we say that (F , A) is a soft subset of (G , B) if A ⊆ B and for all e ∈ A, F (e) and G(e) are identical approximations.
We write .
Reference
- Maji P. K., Biswas R., Roy A. R., Soft set theory. (English summary), Comput. Math. Appl. 45 (2003), no. 4-5, 555-562.