Using astropy.vo.validator

VO services validator is used by STScI to support Simple Cone Search. Currently, only Cone Search services are supported. A typical user should not need the validator. However, this could be used by VO service providers to validate their services. Currently, any service to be validated has to be registered in STScI VAO Registry.

Validation for Simple Cone Search

astropy.vo.validator.validate validates VO services. Currently, only Cone Search validation is done using check_conesearch_sites(), which utilizes underlying astropy.io.votable.validator library.

A master list of all available Cone Search services is obtained from astropy.vo.validator.Conf.conesearch_master_list, which is a URL query to STScI VAO Registry by default. However, by default, only the ones in astropy.vo.validator.Conf.conesearch_urls are validated (also see Default Cone Search Services), while the rest are skipped. There are also options to validate a user-defined list of services or all of them.

All Cone Search queries are done using RA, DEC, and SR given by <testQuery> XML tag in the registry, and maximum verbosity. In an uncommon case where <testQuery> is not defined for a service, it uses a default search for RA=0&DEC=0&SR=0.1.

The results are separated into 4 groups below. Each group is stored as a JSON file of VOSDatabase:

1. conesearch_good.json Passed validation without critical

   warnings and exceptions. This database residing in astropy.vo.Conf.vos_baseurl is the one used by Simple Cone Search by default.

2. conesearch_warn.json Has critical warnings but no

   exceptions. Users can manually set astropy.vo.Conf.conesearch_dbname to use this at their own risk.

3. conesearch_exception.json

   Has some exceptions. Never use this. For informational purpose only.

4. conesearch_error.json

   Has network connection error. Never use this. For informational purpose only.

HTML pages summarizing the validation results are stored in 'results' sub-directory, which also contains downloaded XML files from individual Cone Search queries.

Warnings and Exceptions

A subset of astropy.io.votable.exceptions that is considered non-critical is defined by astropy.vo.validator.Conf.noncritical_warnings, which will not be flagged as bad by the validator. However, this does not change the behavior of astropy.io.votable.Conf.pedantic, which still needs to be set to False for them not to be thrown out by conesearch(). Despite being listed as non-critical, user is responsible to check whether the results are reliable; They should not be used blindly.

Some units recognized by VizieR are considered invalid by Cone Search standards. As a result, they will give the warning 'W50', which is non-critical by default.

User can also modify astropy.vo.validator.Conf.noncritical_warnings to include or exclude any warnings or exceptions, as desired. However, this should be done with caution. Adding exceptions to non-critical list is not recommended.

Building the Database from Registry

Each Cone Search service is a VOSCatalog in a VOSDatabase (see Catalog Manipulation and Database Manipulation).

In the master registry, there are duplicate catalog titles with different access URLs, duplicate access URLs with different titles, duplicate catalogs with slightly different descriptions, etc.

A Cone Search service is really defined by its access URL regardless of title, description, etc. By default, from_registry() ensures each access URL is unique across the database. However, for user-friendly catalog listing, its title will be the catalog key, not the access URL.

In the case of two different access URLs sharing the same title, each URL will have its own database entry, with a sequence number appended to their titles (e.g., ‘Title 1’ and ‘Title 2’). For consistency, even if the title does not repeat, it will still be renamed to ‘Title 1’.

In the case of the same access URL appearing multiple times in the registry, the validator will store the first catalog with that access URL and throw out the rest. However, it will keep count of the number of duplicates thrown out in the 'duplicatesIgnored' dictionary key of the catalog kept in the database.

All the existing catalog tags will be copied over as dictionary keys, except 'accessURL' that is renamed to 'url' for simplicity. In addition, new keys from validation are added:

• validate_expected

  Expected validation result category, e.g., “good”.

• validate_network_error

  Indication for connection error.

• validate_nexceptions

  Number of exceptions found.

• validate_nwarnings

  Number of warnings found.

• validate_out_db_name

  Cone Search database name this entry belongs to.

• validate_version

  Version of validation software.

• validate_warning_types

  List of warning codes.

• validate_warnings

  Descriptions of the warnings.

• validate_xmllint

  Indication of whether xmllint passed.

• validate_xmllint_content

  Output from xmllint.

Configurable Items

These parameters are set via Configuration system (astropy.config):

• astropy.vo.validator.Conf.conesearch_master_list

  VO registry query URL that should return a VO table with all the desired VO services.

• astropy.vo.validator.Conf.conesearch_urls

  Subset of Cone Search access URLs to validate.

• astropy.vo.validator.Conf.noncritical_warnings

  List of VO table parser warning codes that are considered non-critical.

Also depends on properties in Simple Cone Search Configurable Items.

Examples

>>> from astropy.vo.validator import validate

Validate default Cone Search sites with multiprocessing and write results in the current directory. Reading the master registry can be slow, so the default timeout is internally set to 60 seconds for it. However, astropy.utils.data.REMOTE_TIMEOUT should still be set to account for accessing the individual services (at least 30 seconds is recommended). In addition, all VO table warnings from the registry are suppressed because we are not trying to validate the registry itself but the services it contains:

>>> from astropy.utils import data
>>> with data.conf.set_temp('remote_timeout', 30):
...     validate.check_conesearch_sites()
Downloading http://vao.stsci.edu/directory/NVORegInt.asmx/...
|===========================================|  25M/ 25M (100.00%)        00s
INFO: Only 30/11938 site(s) are validated [astropy.vo.validator.validate]
# ...
INFO: good: 14 catalog(s) [astropy.vo.validator.validate]
INFO: warn: 12 catalog(s) [astropy.vo.validator.validate]
INFO: excp: 0 catalog(s) [astropy.vo.validator.validate]
INFO: nerr: 4 catalog(s) [astropy.vo.validator.validate]
INFO: total: 30 out of 30 catalog(s) [astropy.vo.validator.validate]
INFO: check_conesearch_sites took 451.05685997 s on AVERAGE...

Validate only Cone Search access URLs hosted by 'stsci.edu' without verbose outputs (except warnings that are controlled by warnings) or multiprocessing, and write results in 'subset' sub-directory instead of the current directory. For this example, we use registry_db from VO database examples:

>>> urls = registry_db.list_catalogs_by_url(pattern='stsci.edu')
>>> urls
['http://archive.stsci.edu/befs/search.php?',
 'http://archive.stsci.edu/copernicus/search.php?', ...,
 'http://galex.stsci.edu/gxWS/ConeSearch/gxConeSearch.aspx?',
 'http://gsss.stsci.edu/webservices/vo/ConeSearch.aspx?CAT=GSC23&']
>>> with data.conf.set_temp('remote_timeout', 30):
...     validate.check_conesearch_sites(
...         destdir='./subset', verbose=False, parallel=False, url_list=urls)
INFO: check_conesearch_sites took 84.7241549492 s on AVERAGE...

Add 'W24' from astropy.io.votable.exceptions to the list of non-critical warnings to be ignored and re-run default validation. This is not recommended unless you know exactly what you are doing:

>>> from astropy.vo.validator.validate import conf
>>> with conf.set_temp('noncritical_warnings', conf.noncritical_warnings + ['W24']):
...     with data.conf.set_temp('remote_timeout', 30):
...         validate.check_conesearch_sites()

Validate all Cone Search services in the master registry (this will take a while) and write results in 'all' sub-directory:

>>> with data.conf.set_temp('remote_timeout', 30):
...     validate.check_conesearch_sites(destdir='./all', url_list=None)

To look at the HTML pages of the validation results in the current directory using Firefox browser (images shown are from STScI server but your own results should look similar):

firefox results/index.html

When you click on ‘All tests’ from the page above, you will see all the Cone Search services validated with a summary of validation results:

When you click on any of the listed URLs from above, you will see detailed validation warnings and exceptions for the selected URL:

When you click on the URL on top of the page above, you will see the actual VO Table returned by the Cone Search query:

Inspection of Validation Results

astropy.vo.validator.inspect inspects results from Validation for Simple Cone Search. It reads in JSON files of VOSDatabase residing in astropy.vo.Conf.vos_baseurl, which can be changed to point to a different location.

Configurable Items

This parameter is set via Configuration system (astropy.config):

• astropy.vo.Conf.vos_baseurl

Examples

>>> from astropy.vo.validator import inspect

Load Cone Search validation results from astropy.vo.Conf.vos_baseurl (by default, the one used by Simple Cone Search):

>>> r = inspect.ConeSearchResults()
Downloading http://.../conesearch_good.json
|===========================================|  48k/ 48k (100.00%)        00s
Downloading http://.../conesearch_warn.json
|===========================================|  85k/ 85k (100.00%)        00s
Downloading http://.../conesearch_exception.json
|===========================================| 3.0k/3.0k (100.00%)        00s
Downloading http://.../conesearch_error.json
|===========================================| 4.0k/4.0k (100.00%)        00s

Print tally. In this example, there are 13 Cone Search services that passed validation with non-critical warnings, 14 with critical warnings, 1 with exceptions, and 2 with network error:

>>> r.tally()
good: 13 catalog(s)
warn: 14 catalog(s)
exception: 1 catalog(s)
error: 2 catalog(s)
total: 30 catalog(s)

Print a list of good Cone Search catalogs, each with title, access URL, warning codes collected, and individual warnings:

>>> r.list_cats('good')
Guide Star Catalog 2.3 1
http://gsss.stsci.edu/webservices/vo/ConeSearch.aspx?CAT=GSC23&
W48,W50
.../vo.xml:136:0: W50: Invalid unit string 'pixel'
.../vo.xml:155:0: W48: Unknown attribute 'nrows' on TABLEDATA
# ...
USNO-A2 Catalogue 1
http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?CAT=USNO-A2&
W17,W42,W21
.../vo.xml:4:0: W21: vo.table is designed for VOTable version 1.1 and 1.2...
.../vo.xml:4:0: W42: No XML namespace specified
.../vo.xml:15:15: W17: VOTABLE element contains more than one DESCRIPTION...

List Cone Search catalogs with warnings, excluding warnings that were ignored in astropy.vo.validator.Conf.noncritical_warnings, and writes the output to a file named 'warn_cats.txt' in the current directory. This is useful to see why the services failed validations:

>>> with open('warn_cats.txt', 'w') as fout:
...     r.list_cats('warn', fout=fout, ignore_noncrit=True)

List the titles of all good Cone Search catalogs:

>>> r.catkeys['good']
[u'Guide Star Catalog 2.3 1',
 u'SDSS DR7 - Sloan Digital Sky Survey Data Release 7 1',
 u'SDSS DR7 - Sloan Digital Sky Survey Data Release 7 2',
 u'SDSS DR7 - Sloan Digital Sky Survey Data Release 7 3', ...,
 u'USNO-A2 Catalogue 1']

Print the details of catalog titled 'USNO-A2 Catalogue 1':

>>> r.print_cat('USNO-A2 Catalogue 1')
{
    "capabilityClass": "ConeSearch",
    "capabilityStandardID": "ivo://ivoa.net/std/ConeSearch",
    "capabilityValidationLevel": "",
    "contentLevel": "#University#Research#Amateur#",
    # ...
    "version": "",
    "waveband": "#Optical#"
}
Found in good

Load Cone Search validation results from a local directory named 'subset'. This is useful if you ran your own Validation for Simple Cone Search and wish to inspect the output databases. This example reads in validation of STScI Cone Search services done in Validation for Simple Cone Search Examples:

>>> from astropy.vo import conf
>>> with conf.set_temp('vos_baseurl', './subset/'):
>>>     r = inspect.ConeSearchResults()
>>> r.tally()
good: 19 catalog(s)
warn: 7 catalog(s)
exception: 2 catalog(s)
error: 0 catalog(s)
total: 28 catalog(s)
>>> r.catkeys['good']
[u'Advanced Camera for Surveys 1',
 u'Berkeley Extreme and Far-UV Spectrometer 1',
 u'Copernicus Satellite 1',
 u'Extreme Ultraviolet Explorer 1', ...,
 u'Wisconsin Ultraviolet Photo-Polarimeter Experiment 1']