2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/39779We discuss the role of some nonpartonic effects which lead to $N_p^{π^+} \ne N_n^{π^+}$ and $N_p^{π^-} \ne N_n^{π^-}$ and may therefore modify the conclusionon the $\bar d - \bar u$ asymmetry extracted from semi-inclusive production of pions in DIS. Quantitative estimations for resolved photon and exclusive $ρ^0$ are given as examples. The results are discussed in the context of recent HERMES data.A talk given at the workshop "Meson2000", Cracow, Poland, 19-23 May 2000High Energy Physics - Phenomenologytext