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 domutils import getElementsByName, getElementByName

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


    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.
        layers = []


    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 lower(foo.childNodes[0].data) != '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 lower(foo.childNodes[0].data) != 'none':
            self.access = foo.childNodes[0].data
        
        # Extract output format information
        foo = getElementsByName(
            getElementByName(getElementByName(getElementByName(
            root, 'Capability'), 'Request'), 'GetMap'), 'Format')
        self.formats = map((lambda i: i.childNodes[0].data), foo)

        # 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

        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:
                    self.layers[index]['srs'].append(srs)
                except KeyError:
                    self.layers[index]['srs'] = [srs]

        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]

        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

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

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