# 31. Handling custom defined tags in QuakeML and the ObsPy Catalog/Event framework

QuakeML allows use of custom elements in addition to the ‘usual’ information defined by the QuakeML standard. It allows a) custom namespace attributes to QuakeML namespace tags and b) custom namespace subtags to QuakeML namespace elements. ObsPy can handle both basic custom tags in event type objects (a) and custom attributes (b) during input/output to/from QuakeML. The following basic example illustrates how to output a valid QuakeML file with custom xml tags/attributes:

    from obspy import Catalog, UTCDateTime

    extra = {'my_tag': {'value': True,
                        'namespace': 'http://some-page.de/xmlns/1.0',
                        'attrib': {'{http://some-page.de/xmlns/1.0}my_attrib1': '123.4',
                                   '{http://some-page.de/xmlns/1.0}my_attrib2': '567'}},
             'my_tag_2': {'value': u'True',
                          'namespace': 'http://some-page.de/xmlns/1.0'},
             'my_tag_3': {'value': 1,
                          'namespace': 'http://some-page.de/xmlns/1.0'},
             'my_tag_4': {'value': UTCDateTime('2013-01-02T13:12:14.600000Z'),
                          'namespace': 'http://test.org/xmlns/0.1'},
             'my_attribute': {'value': 'my_attribute_value',
                              'type': 'attribute',
                              'namespace': 'http://test.org/xmlns/0.1'}}

    cat = Catalog()
    cat.extra = extra
    cat.write('my_catalog.xml', format='QUAKEML',
              nsmap={'my_ns': 'http://test.org/xmlns/0.1'})

All custom information to be stored in the customized QuakeML has to be stored in form of a `dict` or `AttribDict` object as the `extra` attribute of the object that should carry the additional custom information (e.g. `Catalog`, `Event`, `Pick`). The keys are used as the name of the xml tag, the content of the xml tag is defined in a simple dictionary: `'value'` defines the content of the tag (the string representation of the object gets stored in the textual xml output). `'namespace'` has to specify a custom namespace for the tag. `'type'` can be used to specify whether the extra information should be stored as a subelement (`'element'`, default) or as an attribute (`'attribute'`). Attributes to custom subelements can be provided in form of a dictionary as `'attrib'`. If desired for better (human-)readability, namespace abbreviations in the output xml can be specified during output as QuakeML by providing a dictionary of namespace abbreviation mappings as nsmap parameter to `Catalog.write()`. The xml output of the above example looks like:

    <?xml version='1.0' encoding='utf-8'?>
    <q:quakeml xmlns:q='http://quakeml.org/xmlns/quakeml/1.2'
               xmlns:ns0='http://some-page.de/xmlns/1.0'
               xmlns:my_ns='http://test.org/xmlns/0.1'
               xmlns='http://quakeml.org/xmlns/bed/1.2'>
      <eventParameters publicID='smi:local/b425518c-9445-40c7-8284-d1f299ed2eac'
                       my_ns:my_attribute='my_attribute_value'>
        <ns0:my_tag ns0:my_attrib1='123.4' ns0:my_attrib2='567'>true</ns0:my_tag>
        <my_ns:my_tag_4>2013-01-02T13:12:14.600000Z</my_ns:my_tag_4>
        <ns0:my_tag_2>True</ns0:my_tag_2>
        <ns0:my_tag_3>1</ns0:my_tag_3>
      </eventParameters>
    </q:quakeml>

When reading the above xml again, using `read_events()`, the custom tags get parsed and attached to the respective Event type objects (in this example to the Catalog object) as `.extra`. Note that all values are read as text strings:

    from obspy import read_events

    cat = read_events('my_catalog.xml')
    print(cat.extra)

    AttribDict({u'my_tag': {u'attrib': {'{http://some-page.de/xmlns/1.0}my_attrib2': '567',
                                        '{http://some-page.de/xmlns/1.0}my_attrib1': '123.4'},
                            u'namespace': u'http://some-page.de/xmlns/1.0',
                            u'value': 'true'},
                u'my_tag_4': {u'namespace': u'http://test.org/xmlns/0.1',
                              u'value': '2013-01-02T13:12:14.600000Z'},
                u'my_attribute': {u'type': u'attribute',
                                  u'namespace': u'http://test.org/xmlns/0.1',
                                  u'value': 'my_attribute_value'},
                u'my_tag_2': {u'namespace': u'http://some-page.de/xmlns/1.0',
                              u'value': 'True'},
                u'my_tag_3': {u'namespace': u'http://some-page.de/xmlns/1.0',
                              u'value': '1'}})

Custom tags can be nested:

    from obspy import Catalog
    from obspy.core import AttribDict

    ns = 'http://some-page.de/xmlns/1.0'

    my_tag = AttribDict()
    my_tag.namespace = ns
    my_tag.value = AttribDict()

    my_tag.value.my_nested_tag1 = AttribDict()
    my_tag.value.my_nested_tag1.namespace = ns
    my_tag.value.my_nested_tag1.value = 1.23E+10

    my_tag.value.my_nested_tag2 = AttribDict()
    my_tag.value.my_nested_tag2.namespace = ns
    my_tag.value.my_nested_tag2.value = True

    cat = Catalog()
    cat.extra = AttribDict()
    cat.extra.my_tag = my_tag
    cat.write('my_catalog.xml', 'QUAKEML')

This will produce an xml output similar to the following:

    <?xml version='1.0' encoding='utf-8'?>
    <q:quakeml xmlns:q='http://quakeml.org/xmlns/quakeml/1.2'
               xmlns:ns0='http://some-page.de/xmlns/1.0'
               xmlns='http://quakeml.org/xmlns/bed/1.2'>
      <eventParameters publicID='smi:local/97d2b338-0701-41a4-9b6b-5903048bc341'>
        <ns0:my_tag>
          <ns0:my_nested_tag1>12300000000.0</ns0:my_nested_tag1>
          <ns0:my_nested_tag2>true</ns0:my_nested_tag2>
        </ns0:my_tag>
      </eventParameters>
    </q:quakeml>

The output xml can be read again using `read_events()` and the nested tags can be retrieved in the following way:

    from obspy import read_events

    cat = read_events('my_catalog.xml')
    print(cat.extra.my_tag.value.my_nested_tag1.value)
    print(cat.extra.my_tag.value.my_nested_tag2.value)

    12300000000.0
    true

The order of extra tags can be controlled by using an `OrderedDict` for the extra attribute (using a plain dict or `AttribDict` can result in arbitrary order of tags):

    from collections import OrderedDict
    from obspy.core.event import Catalog, Event

    ns = 'http://some-page.de/xmlns/1.0'

    my_tag1 = {'namespace': ns, 'value': 'some value 1'}
    my_tag2 = {'namespace': ns, 'value': 'some value 2'}

    event = Event()
    cat = Catalog(events=[event])
    event.extra = OrderedDict()
    event.extra['myFirstExtraTag'] = my_tag2
    event.extra['mySecondExtraTag'] = my_tag1
    cat.write('my_catalog.xml', 'QUAKEML')

### Thank you!

We would like to thank our contributors, whose efforts make this software what it is. These people have helped by writing code and documentation, and by testing. They have created and maintained this product, its associated libraries and applications, our build tools and our web sites.

#### Contributors

- Ackerley, Nick
- Allgeyer, Sebastien
- Ammon, Charles J.
- Antunes, Emanuel
- Arnarsson, Ólafur St.
- Bank, Markus
- Barsch, Robert
- Behr, Yannik
- Bernardi, Fabrizio
- Bernauer, Felix
- Bes de Berc, Maxime
- Beyreuther, Moritz
- Boltz, Shawn
- Bonaimé, Sébastien
- Carothers, Lloyd
- Chamberlain, Calum
- Chambers, Derrick
- Chen, Zhao
- Clark, Adam
- Danecek, Peter
- Egdorf, Sven
- Engels, Fabian
- Ermert, Laura
- Eulenfeld, Tom

- Fabbri, Tommaso
- Falco, Nicholas
- Fee, Jeremy
- Grellier, Clément
- Grunberg, Marc
- Hammer, Conny
- Heimann, Sebastian
- Heiniger, Lukas
- Hope, Gaute
- Igel, Heiner
- Inza, Adolfo
- Isken, Marius
- Ketchum, David
- Koymans, Mathijs
- Kremers, Simon
- Kress, Victor
- Krieger, Lars
- Krischer, Lion
- Kula, Damian
- Käufl, Paul
- Köhler, Andreas
- Lecocq, Thomas
- Leeman, John
- Legovini, Paride

- Lesage, Philippe
- Li, Yulin
- Lomax, Anthony
- Lopes, Rui L.
- MacCarthy, Jonathan
- Maggi, Alessia
- Martin, Henri
- Medlin, Andrew
- Megies, Tobias
- Meschede, Matthias
- Michelini, Alberto
- Miller, Nathaniel C.
- Morgenstern, Bernhard
- Nof, Ran Novitsky
- Panning, Mark P.
- Parker, Tom
- Pestourie, Romain
- Rapagnani, Giovanni
- Reyes, Celso
- Ringler, Adam
- Rothenhäusler, Nicolas
- Russo, Emiliano
- Sales de Andrade, Elliott

- Satriano, Claudio
- Saul, Joachim
- Scheingraber, Chris
- Schneider, Simon
- Sippl, Christian
- Snoke, Arthur
- Stange, Stefan
- Stähler, Simon C.
- Sullivan, Benjamin
- Tian, Dongdong
- Trabant, Chad
- Trani, Luca
- Uieda, Leonardo
- Walker, Andrew
- Walther, Marcus
- Wassermann, Joachim
- Williams, Mark C.
- Winkelman, Andrew
- Zaccarelli, Riccardo
- Zad, Seyed Kasra Hosseini
- Zhu, Lijun
- van Driel, Martin
- van Wijk, Kasper

#### Funds

ObsPy was partially funded by the

- German Science Foundation (DFG) via grant DFG IG 16/9-1
- German Ministry for Education and Research (BMBF), GEOTECHNOLOGIEN grant 03G0646H.
- NERA project (Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation) under the European Community's Seventh Framework Programme (FP7/2007-2013) grant agreement n° 262330
- Leibniz Institute for Applied Geophysics (LIAG)
- VERCE EU-FP7 project (no. 283543)