XPS is used for surface chemical state identification. But other than that, is XAS just an inverse of XPS?
You could easily google this...
X-ray photoelectron spectroscopy uses low energy monochromatic x-rays to excite electrons from atoms near the surface of a sample. The kinetic energy of the electrons is then measured and then the binding energy of the electrons can be calculated.
X-ray absorption spectroscopy measure the attenuation of a x-ray beam as a function of x-ray wavelength (or energy). So what you are detecting is the absorption edges of the atoms in the sample.