  Attosecond x-ray pulses offer unprecedented opportunities for probing and
triggering new types of ultrafast motion. At the same time, pulse
characterization of x-rays presents new challenges that do not exist in the UV
regime. Inner-shell ionization is the dominant ionization mechanism for x-rays
and it is followed by secondary processes like fluorescence, Auger decay, and
shake-up.In general, we find that inner-shell ionization and secondary
processes can create additional delay-dependent modulations that will affect
pulse reconstruction schemes. Our recently proposed pulse characterization
method [Pabst and Dahlstr\"om, PRA 94, 013411 (2016)], where a bound electron
wavepacket is sequentially photoionized by the attosecond pulse, can be adapted
to mitigate the impact of these effects, thus opening up an avenue for reliable
pulse reconstruction in the x-ray regime.
