Article
Keywords:
monotonic valuations; ideal; semigroup
Summary:
We develop problems of monotonic valuations of triads. A theorem on monotonic valuations of triads of the type $\pi \sigma $ is presented. We study, using the notion of the monotonic valuation, representations of ideals by monotone and subadditive mappings. We prove, for example, that there exists, for each  ideal $J$ of the type $\pi $ on a set $A$, a monotone and subadditive set-mapping $h$ on  $P(A)$ with values in non-negative rational numbers such that $J = h^{-1}{''}\{r\in Q;\,r\geq 0 \& r\doteq 0\}$. Some analogical results are proved for ideals of the types $\sigma ,\,\sigma \pi $ and $\pi \sigma $, too. A problem of an additive representation is also discussed.
References:
                        
[M1] Mlček J.: 
Approximations of $\sigma $-classes and $\pi $-classes. Comment. Math. Univ. Carolinae (1979), 20 669-679. 
MR 0555182[M2] Mlček J.: 
Valuations of structures. Comment. Math. Univ. Carolinae (1979), 20 681-695. 
MR 0555183[M3] Mlček J.: 
Monotonic valuations and valuations of triads of higher types. Comment. Math. Univ. Carolinae (1981), 22 377-398. 
MR 0620373[V] Vopěnka P.: 
Mathematics in the Alternative Set Theory. Teubner Texte, Leipzig, 1979. 
MR 0581368