All xsd files are located at http://fews.wldelft.nl/schemas/version1.0/pi-schemas/. The most up to date versions can be found there. See attached pdf for schema documentation
The following schema's are available:
http://fews.wldelft.nl/schemas/version1.0/pi-schemas/Delft_PI.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_branches.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_cells.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_configupdatescript.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_crosssections.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_datacluster.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_dataclusterdefinition.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_diag.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_latinputs.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_locations.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_mapstacks.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_parameters.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_polygons.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_profiles.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_sharedtypes.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_state.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_table.xsd http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_timeseries.xsd