Summary of existing schemes for the classification of emission-line galaxies at high redshift. Top: results of the reference diagnostic (Kewley et al. 2006) are shown in the log([Oiii] λ5007/Hβ) vs. the log ([Oii] λλ3726 + 3729/Hβ) diagram (left) and in the D_n(4000) vs. diagram (right). The code is blue: SFG; green: Seyfert 2; cyan: LINERs; magenta: composites. Bottom: the results of the high-redshift classifications are shown in the standard log([Oiii] λ5007/Hβ) vs. log([Nii] λ6583/Hα) diagram. Left: the L10 diagnostic (Lamareille 2010). Right: the DEW diagnostic (Stasińska et al. 2006). Same color code as above except green: stands for all AGNs in the bottom-right panel; light blue: SFG/comp; yellow: LIN/comp; orange: SF/Sy2. In bottom-right panel, the long dashed line is the boundary between SFG and AGN used by Stasińska et al. (2006).