Extensions/wms/parser.py

# Copyright (c) 2004 by Intevation GmbH
# Authors:
# Martin Schulze <[email protected]>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

"""
Inspect WMS Capabilities for later processing.

Information should only be retrieved with the proper get*() methods.

class WMSCapabilitiesParser:
    __init__()

    grok(string)

    getTitle()
    getAbstract()
    getFees()
    getAccessConstraints()
    getFormats()
    getLayers()
    getSRS()

    getLayerTitle(layer)
    getLayerSRS(layer)
    getLayerLatLonBBox(layer)
    getLayerBBox(layer, srs)

    isQueryable(layer)

    get_srs_discrepancies()
"""

__version__ = "$Revision$"
# $Source$
# $Id$

import xml.dom.minidom
from xml.dom import Node

from domutils import getElementsByName, getElementByName

from Thuban import _

class WMSCapabilitiesParser:
    """
    Thuban class to parse capabilities supplied as large string.

    This class provides methods to parse and retrieve particular
    information from the WMS capabilities XML.  Information should
    only be extracted by the respective get*() methods.
    """

    layers = None
    title = None
    abstract = None
    fees = None
    access = None
    formats = None
    srs_discrepancies = None
    error = None


    def __init__(self):
        """
        Initialises an instance in this class.
        """

        # Note that we must not initialise internal variables of the
        # class in a mutable way or it will be shared among all
        # instances.  None is immutable, [] is not.
        self.error = []


    def grok(self, data):
        """
        Parses the XML response to a WMS GetCapabilities request.

        Internal datastructure of the class will be filled.
        Information should only be retrieved with the respective
        get*() methods.
        """
        xml_dom = xml.dom.minidom.parseString(data)
        root = xml_dom.documentElement

        # Extract the title
        foo = getElementByName(getElementByName(root, 'Service'), 'Title')
        if foo:
            self.title = foo.childNodes[0].data
        
        # Extract the abstract
        foo = getElementByName(getElementByName(root, 'Service'), 'Abstract')
        if foo and len(foo.childNodes[0].data):
            self.abstract = foo.childNodes[0].data
        
        # Extract fees information
        foo = getElementByName(getElementByName(root, 'Service'), 'Fees')
        if foo and len(foo.childNodes[0].data) \
               and foo.childNodes[0].data.lower() != 'none':
            self.fees = foo.childNodes[0].data
        
        # Extract access information
        foo = getElementByName(getElementByName(root, 'Service'),
                               'AccessConstraints')
        if foo and len(foo.childNodes[0].data) \
               and foo.childNodes[0].data.lower() != 'none':
            self.access = foo.childNodes[0].data
        
        foo = getElementByName(getElementByName(
            root, 'Capability'), 'Request')

        # Need to distinguish between Map and GetMap for v1.0 and v1.1
        bar = getElementByName(foo, 'GetMap')
        if bar:
            # WMS 1.1
            foo = getElementsByName(bar, 'Format')
            self.formats = map((lambda i: i.childNodes[0].data), foo)
        else:
            # WMS 1.0
            foo = getElementByName(getElementByName(
                foo, 'Map'), 'Format')
            for node in foo.childNodes:
                if node.nodeType == Node.ELEMENT_NODE:
                    try:
                        self.formats.append(node.nodeName)
                    except AttributeError:
                        self.formats = [node.nodeName]

        # Extract layer names
        self.layers = []
        self.peekLayers(getElementByName(getElementByName(
            root, 'Capability'), 'Layer'), -1)

        xml_dom.unlink()


    def peekLayers(self, top, parent):
        """
        Inspect the provided DOM fragment referenced as top.

        This method will inspect all included layers and traverse the
        tree recursively in order to fill the internal datastructure.

        Note that SRS other than EPSG:* are not yet supported,
        especially there is no support for AUTO and NONE.
        """

        index = len (self.layers)
        self.layers.append({})
        self.layers[index]['parent'] = parent

        for foo in top.attributes.keys():
            if foo == 'queryable':
                self.layers[index]['queryable'] \
                    = int(top.attributes.get(foo).nodeValue)

        foo = getElementByName(top, 'Title')
        if foo and len(foo.childNodes[0].data):
            self.layers[index]['title'] = foo.childNodes[0].data
        else:
            # A <Title> is required for each layer, <name> is optional
            # See OGC 01-068r3, 7.1.4.5.1 and 7.1.4.5.2
            self.error.append(_("No title found for layer #%d") % index)

        foo = getElementByName(top, 'Name')
        if foo and len(foo.childNodes[0].data):
            self.layers[index]['name'] = foo.childNodes[0].data

        # These values are only used for an integrity check
        for foo in getElementsByName(top, 'SRS'):
            for srs in foo.childNodes[0].data.split(" "):
                if srs[0:5] == 'EPSG:':
                    srs = srs[5:]
                try:
                    int(srs)
                    try:
                        self.layers[index]['srs'].append(srs)
                    except KeyError:
                        self.layers[index]['srs'] = [srs]
                except ValueError:
                    if srs[0:4].upper() == 'AUTO' \
                           or srs[0:4].upper() == 'NONE':
                        try:
                            self.layers[index]['_srs_'].append(srs)
                        except KeyError:
                            self.layers[index]['_srs_'] = [srs]
                    else:
                        self.error.append(_("SRS '%s' is not numerical and not"
                                            " AUTO/NONE in layer '%s'") \
                                          % (srs, self.layers[index]['title']))

        foo = getElementByName(top, 'LatLonBoundingBox')
        if foo is not None:
            self.layers[index]['llbbox'] = {}
            for corner in ['minx', 'miny', 'maxx', 'maxy']:
                self.layers[index]['llbbox'][corner] \
                    = foo.attributes.get(corner).nodeValue

        boxes = getElementsByName(top, 'BoundingBox')
        if boxes != []:
            self.layers[index]['bbox'] = {}
        for foo in boxes:
            srs = foo.attributes.get('SRS').nodeValue
            if srs[0:5] == 'EPSG:':
                srs = srs[5:]
            self.layers[index]['bbox'][srs] = {}
            for corner in ['minx', 'miny', 'maxx', 'maxy']:
                self.layers[index]['bbox'][srs][corner] \
                    = foo.attributes.get(corner).nodeValue
            
        # Traverse subsidiary layers
        sublayer = getElementsByName(top, 'Layer')
        for l in sublayer:
            self.peekLayers(l, index)


    def getTitle(self):
        """
        Returns the main title of the WMS object.

        If no title is provided in the capabilities, an empty string
        is returned.
        """
        if self.title is None:
            return ''
        else:
            return self.title


    def getAbstract(self):
        """
        Returns the abstract of the WMS object.

        If no abstract is provided in the capabilities, an empty
        string is returned.
        """
        if self.abstract is None:
            return ''
        else:
            return self.abstract


    def getFees(self):
        """
        Returns the fees information of the WMS object.

        If no information is provided in the capabilities or if it is
        set to 'none', an empty string is returned.
        """
        if self.fees is None:
            return ''
        else:
            return self.fees


    def getAccessConstraints(self):
        """
        Returns information about access constraints for the WMS object.

        If no information is provided in the capabilities or if it is
        set to 'none', an empty string is returned.
        """
        if self.access is None:
            return ''
        else:
            return self.access


    def getFormats(self):
        """
        Returns a list of supported output formats.

        These are used in the GetMap request.  This method will
        default to 'image/jpeg' if no format is recognised in XML
        Capabilities, assuming that JPEG will always be supported on
        the server side.
        """
        if self.formats is None:
            return ['image/jpeg']
        else:
            return self.formats

    def getLayers(self):
        """
        Returns a list of layer names.

        Only named layers will be returned, since a layer may have a
        title but doesn't have to have a name associated to it as
        well.  If no layers were found, an empty list is returned.
        """
        result = []
        for layer in self.layers:
            if 'name' in layer:
                result.append(layer['name'])

        return result


    def getSRS(self):
        """
        Returns the root list of spatial reference systems (SRS).

        This list is taken from the root layer.  Those SRS are common
        to all subsidiary layers.  If no SRS are common to all layers,
        an empty list is returned.  If no layers were detected, an
        empty list is returned as well.
        """
        if len(self.layers) == 0:
            return []

        # index 0 denotes the root layer by design
        if 'srs' in self.layers[0].keys():
            return self.layers[0]['srs']


    def getLayerTitle(self, name):
        """
        Returns the title of the named layer.

        If no such title or no such layer exists, an empty string is
        returned.
        """
        for layer in self.layers:
            if 'name' in layer:
                if layer['name'] == name:
                    if 'title' in layer:
                        return layer['title']

        return ''


    def getLayerSRS(self, name):
        """
        Returns a list of spacial reference systems (SRS).

        The SRS are specified by the European Petroleum Survey Group
        (EPSG).  There should be at least one SRS per layer, though.
        The prefix 'EPSG:' will be stripped.  If none exists, an empty
        list is returned.

        The specification [OGC 01-068r3] says about inheritance of
        SRS:

        - Every layer is available in one or more SRS (or in an
          undefined SRS)

        - Geographic information whose SRS is undefined
          (e.g. digitised historical maps) shall use 'NONE'
          (case-sensitive).  This implementation does not support
          this.

        - Every layer shall have at least one SRS element that is
          either stated explicitly or inherited from a parent layer.

        - The root layer element shall include a sequence of zero or
          more SRS elements listing all SRS which are common for to
          all subsidiary layers.

        - Layers may optionally add to the global SRS list, or to the
          list inherited from a parent layer.

        - A server which has the ability to transform data to
          different SRSes may choose not to provide an explicit
          BoundingBox for every possible SRS available for each Layer.
          Thus the list of <SRS> elements are authoritative.

        This implementation returns the list of SRS for the given
        layer, calculated by looking at BoundingBoxes defined in the
        named layer and all layers higher in the hierarchy up to the
        root layer which weren't overwritten.
        """
        for i in range(len(self.layers)):
            if 'name' in self.layers[i]:
                if self.layers[i]['name'] == name:
                    pivot = i
                    break
        else:
            return []

        result = []
        while pivot != -1:
            if 'srs' in self.layers[pivot]:
                for srs in self.layers[pivot]['srs']:
                    if srs not in result:
                        result.append(srs)
            pivot = self.layers[pivot]['parent']

        return result


    def getLayerLatLonBBox(self, name):
        """
        Returns a dictionary of the LatLonBoundingBox.

        ... for the named layer if it exists.  The SRS is always
        EPSG:4326 per convention.  There should be at least one,
        though, inherited from the root layer at least.  If none
        exists, the value None is returned.
        """
        for layer in self.layers:
            if 'name' in layer:
                if layer['name'] == name:
                    if 'llbbox' in layer:
                        return layer['llbbox']
                    else:
                        # No LatLonBoundingBox found in current layer,
                        # so traverse the hierarchy upwards and check
                        # again until there is one.
                        pivot = layer
                        while pivot['parent'] != -1:
                            pivot = self.layers[pivot['parent']]
                            if 'llbbox' in pivot:
                                return pivot['llbbox']

        return None


    def getLayerBBox(self, name, srs):
        """
        Returns a dictionary of the BoundingBox.

        If no such BoundingBox exists, None is returned.

        The specification [OGC 01-068r3] says about BoundingBoxes:

        - Layers may have zero or more BoundingBox elements what are
          either stated explicitly or inherited from a parent layer.

        - A layer may have multiple BoundingBox elements, but each one
          shall state a different SRS.

        - A layer inherits any BoundingBoxes defined by its
          parents.

        - A BoundingBox inherited from the parent layer for a
          particular SRS is replaced by any declaration for the same
          SRS in the current layer.

        - A BoundingBox in the child layer for a new SRS which is not
          already declared by the parent, is added to the list of
          BoundingBoxes for the child layer.

        - A single layer shall not contain more than one BoundingBox
          element for the same SRS.
        """
        for layer in self.layers:
            if 'name' in layer:
                if layer['name'] == name:
                    if 'bbox' in layer:
                        if srs in layer['bbox']:
                            return layer['bbox'][srs]
                    
                    # No BoundingBox for the given SRS found in
                    # current layer, so traverse the hierarchy upwards
                    # and check again until there is one.
                    pivot = layer
                    while pivot['parent'] != -1:
                        pivot = self.layers[pivot['parent']]
                        if 'bbox' in pivot:
                            if srs in pivot['bbox']:
                                return pivot['bbox'][srs]

        # No matching BBox found, let's see if it was EPSG:4326
        if srs == '4326':
            return self.getLayerLatLonBBox(name)

        return None


    def isQueryable(self, name):
        """
        Returns the value of the queryable attribute of a layer.

        This attribute denotes whether this layer can be queried
        through the GetFeatureInfo request.  The default value is 0.

        The specification [OGC 01-068r3] this attribute can be
        inherited.
        """

        for layer in self.layers:
            if 'name' in layer:
                if layer['name'] == name:
                    try:
                        return layer['queryable']
                    except KeyError:
                        # No attribute in this layer, so traverse the
                        # hierarchy upwards
                        pivot = layer
                        while pivot['parent'] != -1:
                            pivot = self.layers[pivot['parent']]
                            if 'queryable' in pivot:
                                return pivot['queryable']
        return 0


    def get_srs_discrepancies(self):
        """
        Returns a list of layer identifications where the denoted SRS
        values differ from the calculated ones through BoundingBox
        elements.
        """
        return self.srs_discrepancies


if __name__ == "__main__":
    print "This module cannot be executed standalone."

    import os

    sample = "test/sample.xml"
    try:
        f = open(sample, "r")
    except IOError:
        try:
            f = open(os.path.dirname(__file__) + "/" + sample, "r")
        except IOError:
            print "Cannot open %s for reading" % sample

    if f is not None:
        sample = f.read();
        f.close()
        
        ina = WMSCapabilitiesParser()
        ina.grok(sample)
1	joey	2133	# Copyright (c) 2004 by Intevation GmbH
2			# Authors:
3			# Martin Schulze <[email protected]>
4			#
5			# This program is free software; you can redistribute it and/or modify
6			# it under the terms of the GNU General Public License as published by
7			# the Free Software Foundation; either version 2 of the License, or
8			# (at your option) any later version.
9			#
10			# This program is distributed in the hope that it will be useful,
11			# but WITHOUT ANY WARRANTY; without even the implied warranty of
12			# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13			# GNU General Public License for more details.
14			#
15			# You should have received a copy of the GNU General Public License
16			# along with this program; if not, write to the Free Software
17			# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18
19			"""
20			Inspect WMS Capabilities for later processing.
21
22			Information should only be retrieved with the proper get*() methods.
23
24			class WMSCapabilitiesParser:
25			__init__()
26
27			grok(string)
28
29			getTitle()
30			getAbstract()
31			getFees()
32			getAccessConstraints()
33			getFormats()
34			getLayers()
35			getSRS()
36
37			getLayerTitle(layer)
38			getLayerSRS(layer)
39			getLayerLatLonBBox(layer)
40			getLayerBBox(layer, srs)
41
42			isQueryable(layer)
43
44			get_srs_discrepancies()
45			"""
46
47			__version__ = "$Revision$"
48			# $Source$
49			# $Id$
50
51			import xml.dom.minidom
52	joey	2173	from xml.dom import Node
53	joey	2133
54			from domutils import getElementsByName, getElementByName
55
56	joey	2165	from Thuban import _
57
58	joey	2133	class WMSCapabilitiesParser:
59			"""
60			Thuban class to parse capabilities supplied as large string.
61
62			This class provides methods to parse and retrieve particular
63			information from the WMS capabilities XML. Information should
64			only be extracted by the respective get*() methods.
65			"""
66
67			layers = None
68			title = None
69			abstract = None
70			fees = None
71			access = None
72			formats = None
73			srs_discrepancies = None
74	joey	2165	error = None
75	joey	2133
76
77			def __init__(self):
78			"""
79			Initialises an instance in this class.
80			"""
81
82			# Note that we must not initialise internal variables of the
83			# class in a mutable way or it will be shared among all
84			# instances. None is immutable, [] is not.
85	joey	2165	self.error = []
86	joey	2133
87
88			def grok(self, data):
89			"""
90			Parses the XML response to a WMS GetCapabilities request.
91
92			Internal datastructure of the class will be filled.
93			Information should only be retrieved with the respective
94			get*() methods.
95			"""
96	joey	2153	xml_dom = xml.dom.minidom.parseString(data)
97			root = xml_dom.documentElement
98	joey	2133
99			# Extract the title
100			foo = getElementByName(getElementByName(root, 'Service'), 'Title')
101			if foo:
102			self.title = foo.childNodes[0].data
103
104			# Extract the abstract
105			foo = getElementByName(getElementByName(root, 'Service'), 'Abstract')
106			if foo and len(foo.childNodes[0].data):
107			self.abstract = foo.childNodes[0].data
108
109			# Extract fees information
110			foo = getElementByName(getElementByName(root, 'Service'), 'Fees')
111			if foo and len(foo.childNodes[0].data) \
112	joey	2155	and foo.childNodes[0].data.lower() != 'none':
113	joey	2133	self.fees = foo.childNodes[0].data
114
115			# Extract access information
116			foo = getElementByName(getElementByName(root, 'Service'),
117			'AccessConstraints')
118			if foo and len(foo.childNodes[0].data) \
119	joey	2155	and foo.childNodes[0].data.lower() != 'none':
120	joey	2133	self.access = foo.childNodes[0].data
121
122	joey	2173	foo = getElementByName(getElementByName(
123			root, 'Capability'), 'Request')
124	joey	2133
125	joey	2173	# Need to distinguish between Map and GetMap for v1.0 and v1.1
126			bar = getElementByName(foo, 'GetMap')
127			if bar:
128			# WMS 1.1
129			foo = getElementsByName(bar, 'Format')
130			self.formats = map((lambda i: i.childNodes[0].data), foo)
131			else:
132			# WMS 1.0
133			foo = getElementByName(getElementByName(
134			foo, 'Map'), 'Format')
135			for node in foo.childNodes:
136			if node.nodeType == Node.ELEMENT_NODE:
137			try:
138			self.formats.append(node.nodeName)
139			except AttributeError:
140			self.formats = [node.nodeName]
141
142	joey	2133	# Extract layer names
143			self.layers = []
144			self.peekLayers(getElementByName(getElementByName(
145			root, 'Capability'), 'Layer'), -1)
146
147	joey	2153	xml_dom.unlink()
148	joey	2133
149	joey	2153
150	joey	2133	def peekLayers(self, top, parent):
151			"""
152			Inspect the provided DOM fragment referenced as top.
153
154			This method will inspect all included layers and traverse the
155			tree recursively in order to fill the internal datastructure.
156
157			Note that SRS other than EPSG:* are not yet supported,
158			especially there is no support for AUTO and NONE.
159			"""
160
161			index = len (self.layers)
162			self.layers.append({})
163			self.layers[index]['parent'] = parent
164
165			for foo in top.attributes.keys():
166			if foo == 'queryable':
167			self.layers[index]['queryable'] \
168			= int(top.attributes.get(foo).nodeValue)
169
170			foo = getElementByName(top, 'Title')
171			if foo and len(foo.childNodes[0].data):
172			self.layers[index]['title'] = foo.childNodes[0].data
173	joey	2165	else:
174			# A <Title> is required for each layer, <name> is optional
175			# See OGC 01-068r3, 7.1.4.5.1 and 7.1.4.5.2
176			self.error.append(_("No title found for layer #%d") % index)
177	joey	2133
178			foo = getElementByName(top, 'Name')
179			if foo and len(foo.childNodes[0].data):
180			self.layers[index]['name'] = foo.childNodes[0].data
181
182			# These values are only used for an integrity check
183			for foo in getElementsByName(top, 'SRS'):
184			for srs in foo.childNodes[0].data.split(" "):
185			if srs[0:5] == 'EPSG:':
186			srs = srs[5:]
187			try:
188	joey	2167	int(srs)
189			try:
190			self.layers[index]['srs'].append(srs)
191			except KeyError:
192			self.layers[index]['srs'] = [srs]
193			except ValueError:
194			if srs[0:4].upper() == 'AUTO' \
195			or srs[0:4].upper() == 'NONE':
196			try:
197			self.layers[index]['_srs_'].append(srs)
198			except KeyError:
199			self.layers[index]['_srs_'] = [srs]
200			else:
201			self.error.append(_("SRS '%s' is not numerical and not"
202			" AUTO/NONE in layer '%s'") \
203			% (srs, self.layers[index]['title']))
204	joey	2133
205			foo = getElementByName(top, 'LatLonBoundingBox')
206			if foo is not None:
207			self.layers[index]['llbbox'] = {}
208			for corner in ['minx', 'miny', 'maxx', 'maxy']:
209			self.layers[index]['llbbox'][corner] \
210			= foo.attributes.get(corner).nodeValue
211
212			boxes = getElementsByName(top, 'BoundingBox')
213			if boxes != []:
214			self.layers[index]['bbox'] = {}
215			for foo in boxes:
216			srs = foo.attributes.get('SRS').nodeValue
217			if srs[0:5] == 'EPSG:':
218			srs = srs[5:]
219			self.layers[index]['bbox'][srs] = {}
220			for corner in ['minx', 'miny', 'maxx', 'maxy']:
221			self.layers[index]['bbox'][srs][corner] \
222			= foo.attributes.get(corner).nodeValue
223
224			# Traverse subsidiary layers
225			sublayer = getElementsByName(top, 'Layer')
226			for l in sublayer:
227			self.peekLayers(l, index)
228
229
230			def getTitle(self):
231			"""
232			Returns the main title of the WMS object.
233
234			If no title is provided in the capabilities, an empty string
235			is returned.
236			"""
237			if self.title is None:
238			return ''
239			else:
240			return self.title
241
242
243			def getAbstract(self):
244			"""
245			Returns the abstract of the WMS object.
246
247			If no abstract is provided in the capabilities, an empty
248			string is returned.
249			"""
250			if self.abstract is None:
251			return ''
252			else:
253			return self.abstract
254
255
256			def getFees(self):
257			"""
258			Returns the fees information of the WMS object.
259
260			If no information is provided in the capabilities or if it is
261			set to 'none', an empty string is returned.
262			"""
263			if self.fees is None:
264			return ''
265			else:
266			return self.fees
267
268
269			def getAccessConstraints(self):
270			"""
271			Returns information about access constraints for the WMS object.
272
273			If no information is provided in the capabilities or if it is
274			set to 'none', an empty string is returned.
275			"""
276			if self.access is None:
277			return ''
278			else:
279			return self.access
280
281
282			def getFormats(self):
283			"""
284			Returns a list of supported output formats.
285
286			These are used in the GetMap request. This method will
287			default to 'image/jpeg' if no format is recognised in XML
288			Capabilities, assuming that JPEG will always be supported on
289			the server side.
290			"""
291			if self.formats is None:
292			return ['image/jpeg']
293			else:
294			return self.formats
295
296			def getLayers(self):
297			"""
298			Returns a list of layer names.
299
300			Only named layers will be returned, since a layer may have a
301			title but doesn't have to have a name associated to it as
302			well. If no layers were found, an empty list is returned.
303			"""
304			result = []
305			for layer in self.layers:
306			if 'name' in layer:
307			result.append(layer['name'])
308
309			return result
310
311
312			def getSRS(self):
313			"""
314			Returns the root list of spatial reference systems (SRS).
315
316			This list is taken from the root layer. Those SRS are common
317			to all subsidiary layers. If no SRS are common to all layers,
318			an empty list is returned. If no layers were detected, an
319			empty list is returned as well.
320			"""
321			if len(self.layers) == 0:
322			return []
323
324			# index 0 denotes the root layer by design
325			if 'srs' in self.layers[0].keys():
326			return self.layers[0]['srs']
327
328
329			def getLayerTitle(self, name):
330			"""
331			Returns the title of the named layer.
332
333			If no such title or no such layer exists, an empty string is
334			returned.
335			"""
336			for layer in self.layers:
337			if 'name' in layer:
338			if layer['name'] == name:
339			if 'title' in layer:
340			return layer['title']
341
342			return ''
343
344
345			def getLayerSRS(self, name):
346			"""
347			Returns a list of spacial reference systems (SRS).
348
349			The SRS are specified by the European Petroleum Survey Group
350			(EPSG). There should be at least one SRS per layer, though.
351			The prefix 'EPSG:' will be stripped. If none exists, an empty
352			list is returned.
353
354			The specification [OGC 01-068r3] says about inheritance of
355			SRS:
356
357			- Every layer is available in one or more SRS (or in an
358			undefined SRS)
359
360			- Geographic information whose SRS is undefined
361			(e.g. digitised historical maps) shall use 'NONE'
362			(case-sensitive). This implementation does not support
363			this.
364
365			- Every layer shall have at least one SRS element that is
366			either stated explicitly or inherited from a parent layer.
367
368			- The root layer element shall include a sequence of zero or
369			more SRS elements listing all SRS which are common for to
370			all subsidiary layers.
371
372			- Layers may optionally add to the global SRS list, or to the
373			list inherited from a parent layer.
374
375	joey	2144	- A server which has the ability to transform data to
376			different SRSes may choose not to provide an explicit
377			BoundingBox for every possible SRS available for each Layer.
378			Thus the list of <SRS> elements are authoritative.
379
380	joey	2133	This implementation returns the list of SRS for the given
381			layer, calculated by looking at BoundingBoxes defined in the
382			named layer and all layers higher in the hierarchy up to the
383			root layer which weren't overwritten.
384			"""
385			for i in range(len(self.layers)):
386			if 'name' in self.layers[i]:
387			if self.layers[i]['name'] == name:
388			pivot = i
389			break
390			else:
391			return []
392
393			result = []
394			while pivot != -1:
395	joey	2144	if 'srs' in self.layers[pivot]:
396			for srs in self.layers[pivot]['srs']:
397	joey	2133	if srs not in result:
398			result.append(srs)
399			pivot = self.layers[pivot]['parent']
400
401			return result
402
403
404			def getLayerLatLonBBox(self, name):
405			"""
406			Returns a dictionary of the LatLonBoundingBox.
407
408			... for the named layer if it exists. The SRS is always
409			EPSG:4326 per convention. There should be at least one,
410			though, inherited from the root layer at least. If none
411			exists, the value None is returned.
412			"""
413			for layer in self.layers:
414			if 'name' in layer:
415			if layer['name'] == name:
416			if 'llbbox' in layer:
417			return layer['llbbox']
418			else:
419			# No LatLonBoundingBox found in current layer,
420			# so traverse the hierarchy upwards and check
421			# again until there is one.
422			pivot = layer
423			while pivot['parent'] != -1:
424			pivot = self.layers[pivot['parent']]
425			if 'llbbox' in pivot:
426			return pivot['llbbox']
427
428			return None
429
430
431			def getLayerBBox(self, name, srs):
432			"""
433			Returns a dictionary of the BoundingBox.
434
435			If no such BoundingBox exists, None is returned.
436
437			The specification [OGC 01-068r3] says about BoundingBoxes:
438
439			- Layers may have zero or more BoundingBox elements what are
440			either stated explicitly or inherited from a parent layer.
441
442			- A layer may have multiple BoundingBox elements, but each one
443			shall state a different SRS.
444
445			- A layer inherits any BoundingBoxes defined by its
446			parents.
447
448			- A BoundingBox inherited from the parent layer for a
449			particular SRS is replaced by any declaration for the same
450			SRS in the current layer.
451
452			- A BoundingBox in the child layer for a new SRS which is not
453			already declared by the parent, is added to the list of
454			BoundingBoxes for the child layer.
455
456			- A single layer shall not contain more than one BoundingBox
457			element for the same SRS.
458			"""
459			for layer in self.layers:
460			if 'name' in layer:
461			if layer['name'] == name:
462			if 'bbox' in layer:
463			if srs in layer['bbox']:
464			return layer['bbox'][srs]
465
466			# No BoundingBox for the given SRS found in
467			# current layer, so traverse the hierarchy upwards
468			# and check again until there is one.
469			pivot = layer
470			while pivot['parent'] != -1:
471			pivot = self.layers[pivot['parent']]
472			if 'bbox' in pivot:
473			if srs in pivot['bbox']:
474			return pivot['bbox'][srs]
475
476	joey	2170	# No matching BBox found, let's see if it was EPSG:4326
477			if srs == '4326':
478			return self.getLayerLatLonBBox(name)
479
480	joey	2133	return None
481
482
483			def isQueryable(self, name):
484			"""
485			Returns the value of the queryable attribute of a layer.
486
487			This attribute denotes whether this layer can be queried
488			through the GetFeatureInfo request. The default value is 0.
489
490			The specification [OGC 01-068r3] this attribute can be
491			inherited.
492			"""
493
494			for layer in self.layers:
495			if 'name' in layer:
496			if layer['name'] == name:
497			try:
498			return layer['queryable']
499			except KeyError:
500			# No attribute in this layer, so traverse the
501			# hierarchy upwards
502			pivot = layer
503			while pivot['parent'] != -1:
504			pivot = self.layers[pivot['parent']]
505			if 'queryable' in pivot:
506			return pivot['queryable']
507			return 0
508
509
510			def get_srs_discrepancies(self):
511			"""
512			Returns a list of layer identifications where the denoted SRS
513			values differ from the calculated ones through BoundingBox
514			elements.
515			"""
516			return self.srs_discrepancies
517
518
519			if __name__ == "__main__":
520			print "This module cannot be executed standalone."
521
522			import os
523
524	joey	2164	sample = "test/sample.xml"
525	joey	2133	try:
526	joey	2164	f = open(sample, "r")
527	joey	2133	except IOError:
528			try:
529	joey	2164	f = open(os.path.dirname(__file__) + "/" + sample, "r")
530	joey	2133	except IOError:
531	joey	2164	print "Cannot open %s for reading" % sample
532	joey	2133
533			if f is not None:
534			sample = f.read();
535			f.close()
536
537			ina = WMSCapabilitiesParser()
538			ina.grok(sample)
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