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DEPRECATED this module since it has been merged into ckanext-spatial.
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David Read
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Oct 19, 2012
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| =========== | ||
| ckanext-csw | ||
| =========== | ||
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| .. warning:: | ||
| This module is DEPRECATED as of 19/10/12. It has been merged into https://github.com/okfn/ckanext-spatial | ||
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| ckanext-csw is made of several distinct parts: | ||
| * CSW Server - a basic CSW server - to serve metadata from the CKAN instance | ||
| * CSW Client - a basic client for accessing a CSW server | ||
| * cswinfo - a command-line tool to help making requests of any CSW server | ||
| * Validator - a python library that uses Schematron to validate geographic metadata XML | ||
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| CSW (Catalogue Service for the Web) is an OGC standard for a web interface that allows you to access metadata (which are records that describe data or services) | ||
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| CSW Server | ||
| ========== | ||
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| The currently supported methods with this CSW Server are: | ||
| * GetCapabilities | ||
| * GetRecords | ||
| * GetRecordById | ||
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| ckanext-csw provides the CSW service at ``/csw``. | ||
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| For example you can ask the capabilities of the CSW server installed into CKAN running on 127.0.0.1:5000 like this:: | ||
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| curl 'http://127.0.0.1:5000/csw?request=GetCapabilities&service=CSW' | ||
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| The standard CSW response is in XML format. | ||
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| CSW Client | ||
| ========== | ||
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| CswService is a client for python software (such as the CSW Harvester in ckanext-inspire) to conveniently access a CSW server, using the same three methods as the CSW Server supports. It is a wrapper around OWSLib's tool, dealing with the details of the calls and responses to make it very convenient to use, whereas OWSLib on its own is more complicated. | ||
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| cswinfo tool | ||
| ============ | ||
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| When ckanext-csw is installed, it provides a command-line tool ``cswinfo``, for making queries on CSW servers and returns the info in nicely formatted JSON. This may be more convenient to type than using, for example, curl. | ||
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| Currently available queries are: | ||
| * getcapabilities | ||
| * getidentifiers | ||
| * getrecords | ||
| * getrecordbyid | ||
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| For details, type:: | ||
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| cswinfo csw -h | ||
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| There are options for querying by only certain types, keywords and typenames as well as configuring the ElementSetName. | ||
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| The equivalent example to the one above for asking the cabailities is:: | ||
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| $ cswinfo csw getcapabilities http://127.0.0.1:5000/csw | ||
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| OWSLib is the library used to actually perform the queries. | ||
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| Validator | ||
| ========= | ||
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| This python library uses Schematron and other schemas to validate the XML. | ||
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| Here is a simple example of using the Validator library: | ||
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| from ckanext.csw.validation import Validator | ||
| xml = etree.fromstring(gemini_string) | ||
| validator = Validator(profiles=('iso19139', 'gemini2', 'constraints')) | ||
| valid, messages = validator.isvalid(xml) | ||
| if not valid: | ||
| print "Validation error: " + messages[0] + ':\n' + '\n'.join(messages[1:]) | ||
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| In DGU, the Validator is integrated here: | ||
| https://github.com/okfn/ckanext-inspire/blob/master/ckanext/inspire/harvesters.py#L88 | ||
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| NOTE: The ISO19139 XSD Validator requires system library ``libxml2`` v2.9 (released Sept 2012). If you intend to use this validator then see the section below about installing libxml2. | ||
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| Setup | ||
| ===== | ||
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| Install this extension into your python environment using as usual:: | ||
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| pip install -e git+https://github.com/okfn/ckanext-csw#egg=ckanext-csw | ||
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| This extension requires that ckanext-harvest is also installed - see https://github.com/okfn/ckanext-harvest | ||
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| Currently the library dependencies aren't setup to install automatically, so do this:: | ||
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| pip install owslib 'lxml<=2.2.99' argparse | ||
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| To enable the CSW Server you should adding ``cswserver`` to your ckan.plugins line in your CKAN config file (``harvest`` should be there already from the ckanext-harvest install):: | ||
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| ckan.plugins = harvest cswserver | ||
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| Configure the extension itself with the following keys in your CKAN config file (default values are shown):: | ||
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| cswservice.title = Untitled Service - set cswservice.title in config | ||
| cswservice.abstract = Unspecified service description - set cswservice.abstract in config | ||
| cswservice.keywords = | ||
| cswservice.keyword_type = theme | ||
| cswservice.provider_name = Unnamed provider - set cswservice.provider_name in config | ||
| cswservice.contact_name = No contact - set cswservice.contact_name in config | ||
| cswservice.contact_position = | ||
| cswservice.contact_voice = | ||
| cswservice.contact_fax = | ||
| cswservice.contact_address = | ||
| cswservice.contact_city = | ||
| cswservice.contact_region = | ||
| cswservice.contact_pcode = | ||
| cswservice.contact_country = | ||
| cswservice.contact_email = | ||
| cswservice.contact_hours = | ||
| cswservice.contact_instructions = | ||
| cswservice.contact_role = | ||
| cswservice.rndlog_threshold = 0.01 | ||
| cswservice.log_xml_length = 1000 | ||
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| cswservice.rndlog_threshold is the percentage of interactions to store in the log file. | ||
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| Installing libxml2 | ||
| ================== | ||
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| Version 2.9 is required for the ISO19139 XSD validation. | ||
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| With CKAN you would probably have installed an older version from your distribution. (e.g. with ``sudo apt-get install libxml2-dev``). You need to find the SO files for the old version:: | ||
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| $ find /usr -name "libxml2.so" | ||
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| For example, it may show it here: ``/usr/lib/x86_64-linux-gnu/libxml2.so``. The directory of the SO file is used as a parameter to the ``configure`` next on. | ||
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| Download the libxml2 source:: | ||
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| $ cd ~ | ||
| $ wget ftp://xmlsoft.org/libxml2/libxml2-2.9.0.tar.gz | ||
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| Unzip it:: | ||
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| $ tar zxvf libxml2-2.9.0.tar.gz | ||
| $ cd libxml2-2.9.0/ | ||
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| Configure with the SO directory you found before:: | ||
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| $ ./configure --libdir=/usr/lib/x86_64-linux-gnu | ||
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| Now make it and install it:: | ||
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| $ make | ||
| $ sudo make install | ||
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| Now check the install by running xmllint:: | ||
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| $ xmllint --version | ||
| xmllint: using libxml version 20900 | ||
| compiled with: Threads Tree Output Push Reader Patterns Writer SAXv1 FTP HTTP DTDValid HTML Legacy C14N Catalog XPath XPointer XInclude Iconv ISO8859X Unicode Regexps Automata Expr Schemas Schematron Modules Debug Zlib |