  We consider semi-inclusive unpolarized DIS for the production of charged
kaons and the different possibilities to test the conventionally used
assumptions s-\bar=0 and D_d^{K^+-K^-}=0. The considered tests have the
advantage that they do not require any knowledge of the fragmentation
functions. We also show that measurements of both charged and neutral kaons
would allow the determination of the kaon FFs D_q^{K^++K^-} solely from SIDIS
measurements, and discuss the comparison of (D_u-D_d)^{K^+-K^-} obtained
independently in SIDIS and e+e- reactions. All analysis are performed in LO and
NLO in QCD. The feasibility of the tests to HERMES SIDIS data is considered.
