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	# 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	from xml.dom import Node
53
54	from domutils import getElementsByName, getElementByName
55
56	from Thuban import _
57
58	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	error = None
75
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	self.error = []
86
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	xml_dom = xml.dom.minidom.parseString(data)
97	root = xml_dom.documentElement
98
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	and foo.childNodes[0].data.lower() != 'none':
113	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	and foo.childNodes[0].data.lower() != 'none':
120	self.access = foo.childNodes[0].data
121
122	foo = getElementByName(getElementByName(
123	root, 'Capability'), 'Request')
124
125	# 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	# Extract layer names
143	self.layers = []
144	self.peekLayers(getElementByName(getElementByName(
145	root, 'Capability'), 'Layer'), -1)
146
147	xml_dom.unlink()
148
149
150	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	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
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	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
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	- 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	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	if 'srs' in self.layers[pivot]:
396	for srs in self.layers[pivot]['srs']:
397	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	# No matching BBox found, let's see if it was EPSG:4326
477	if srs == '4326':
478	return self.getLayerLatLonBBox(name)
479
480	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	sample = "test/sample.xml"
525	try:
526	f = open(sample, "r")
527	except IOError:
528	try:
529	f = open(os.path.dirname(__file__) + "/" + sample, "r")
530	except IOError:
531	print "Cannot open %s for reading" % sample
532
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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