using Python lxml to do XML Schema validation on a document, against multiple XML Schema (courtesy @rouault)

validate-multi-xsd

# -*- coding: utf-8 -*-
#-------------------------------------------------------------------------------
# Portions coming from EOxServer
# ( https://github.com/EOxServer/eoxserver/blob/master/eoxserver/services/testbase.py )
#   Copyright (C) 2011 EOX IT Services GmbH
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies of this Software or works derived from this Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#-------------------------------------------------------------------------------

from lxml import etree
import os

def ingest_file_and_strip_mime(filename):
    data = ''
    f = open(filename, 'rb')
    for line in f.readlines():
        if line == '\r\n':
            continue
        if line == '\n':
            continue
        if line.find('Content-Type') >= 0:
            continue
        data = data + line
    f.close()
    return data

def substitute_opengis_schema_location(location, alternate_opengisschemas_location):
    if alternate_opengisschemas_location is not None and \
        location.startswith('http://schemas.opengis.net/'):
        location = alternate_opengisschemas_location + '/' + location[len('http://schemas.opengis.net/'):]
    return location

def validate(xml_filename_or_content, xsd_filename = None, \
             application_schema_ns = 'http://mapserver.gis.umn.edu/mapserver', \
             alternate_opengisschemas_location = 'SCHEMAS_OPENGIS_NET'):

    if xml_filename_or_content.find('<?xml') == 0:
        doc = etree.XML(xml_filename_or_content)
    else:
        doc = etree.XML(ingest_file_and_strip_mime(xml_filename_or_content))

    # Special case if this is a schema
    if doc.tag == '{http://www.w3.org/2001/XMLSchema}schema':
        for child in doc:
            if child.tag == '{http://www.w3.org/2001/XMLSchema}import':
                    location = child.get('schemaLocation')
                    location = substitute_opengis_schema_location(location, alternate_opengisschemas_location)
                    child.set('schemaLocation', location)
        etree.XMLSchema(etree.XML(etree.tostring(doc)))
        return True

    schema_locations = doc.get("{http://www.w3.org/2001/XMLSchema-instance}schemaLocation")

    # Our stripped GetFeature document have an empty timeStamp, put a
    # fake value one instead
    if doc.get('timeStamp') == '':
        doc.set('timeStamp', '1970-01-01T00:00:00Z')

    locations = schema_locations.split()

    # get schema locations
    schema_def = etree.Element("schema", attrib={
            "elementFormDefault": "qualified",
            "version": "1.0.0",
        }, nsmap={
            None: "http://www.w3.org/2001/XMLSchema"
        }
    )

    tempfiles = []

    # Special case for the main application schema
    for ns, location in zip(locations[::2], locations[1::2]):
        if ns == application_schema_ns:
            if xsd_filename is not None:
                location = xsd_filename
            else:
                location = xml_filename[0:-3]+'xsd'

            # Remove mime-type header line if found to generate a valid .xsd
            sanitized_content = ingest_file_and_strip_mime(location)
            location = '/tmp/tmpschema%d.xsd' % len(tempfiles)
            f = open(location, 'wb')
            f.write(sanitized_content)
            tempfiles.append(location)
            f.close()

            xsd = etree.XML(sanitized_content)
            for child in xsd:
                if child.tag == '{http://www.w3.org/2001/XMLSchema}import':
                    sub_ns = child.get('namespace')
                    sub_location = child.get('schemaLocation')
                    sub_location = substitute_opengis_schema_location(sub_location, alternate_opengisschemas_location)
                    etree.SubElement(schema_def, "import", attrib={
                        "namespace": sub_ns,
                        "schemaLocation": sub_location
                        }
                    )

            etree.SubElement(schema_def, "import", attrib={
                    "namespace": ns,
                    "schemaLocation": location
                }
            )

    # Add each schemaLocation as an import
    for ns, location in zip(locations[::2], locations[1::2]):
        if ns == application_schema_ns:
            continue
        location = substitute_opengis_schema_location(location, alternate_opengisschemas_location)
        etree.SubElement(schema_def, "import", attrib={
                "namespace": ns,
                "schemaLocation": location
            }
        )

    # TODO: ugly workaround. But otherwise, the doc is not recognized as schema
    schema = etree.XMLSchema(etree.XML(etree.tostring(schema_def)))

    try:
        schema.assertValid(doc)
        ret = True
    except etree.Error as e:
        print(str(e))
        ret = False

    for filename in tempfiles:
        os.remove(filename)

    return ret