Ubuntu Manpage: stilts-votlint - Validates VOTable documents

NAME

       stilts-votlint - Validates VOTable documents

SYNOPSIS

       stilts votlint [votable=<location>] [ucd=true|false] [unit=true|false] [maxrepeat=<int-
                      value>] [validate=true|false] [version=1.0|1.1|1.2|1.3|1.4]
                      [out=<location>]

DESCRIPTION

The VOTable standard, while not hugely complicated, has a number of subtleties and it's
not difficult to produce VOTable documents which violate it in various ways. In some cases
the errors are small and a parser is likely to process the document without noticing the
trouble. In other cases, the errors are so serious that it's hard for any software to make
sense of it. In many cases in between, different software will react in different ways, in
the worst case appearing to parse a VOTable but in fact understanding the wrong data.

votlint is a program which can check a VOTable document and spot places where it does not
conform to the VOTable standard, or places which look like they may not mean what the
author intended. It is meant for use in two main scenarios:

* For authors of VOTables and VOTable-producing software, to check that the documents they
produce are legal and problem-free.

* For users of VOTables (including authors of VOTable-processing software) who are having
problems with one and want to know whether it is the data or the software at fault.

Validating a VOTable document against the VOTable schema or DTD of course goes a long way
towards checking a VOTable document for errors, but it by no means does the whole job,
simply because the schema/DTD specification languages don't have the facilities to
understand the data structure of a VOTable document. For instance the VOTable schema will
allow any plain text content in a TD element, but whether this makes sense in a VOTable
depends on the datatype attribute of the corresponding FIELD element. There are many other
examples. votlint tackles this by parsing the VOTable document in a way which understands
its structure and assessing the content as critically as it can. For any incorrect or
questionable content it finds, it will output a short message describing the problem and
giving its location in the document. What you do with this information is then up to you.

Using votlint is very straightforward. The votable argument gives the location (filename
or URL) of a VOTable document. Otherwise, the document will be read from standard input.
Error and warning messages will be written on standard output. Each message is prefixed
with the location at which the error was found (if possible the line and column are shown,
though this is dependent on your JVM's default XML parser). If multiple instances of the
same problem are found, by default only a few repeats of the message are reported; this
can be controlled with the maxrepeat parameter. The processing is SAX-based, so
arbitrarily long tables can be processed without heavy memory use.

votlint can't guarantee to pick up every possible error in a VOTable document, but it
ought to pick up many of the most serious errors that are commonly made in authoring
VOTables.

Note: votlint's handling of XML namespaces seems to be somewhat dependent on the XML
parser in use. As far as I can see, Crimson (the default in many JREs) works for any
namespace arrangements, but Xerces seems to have problems when validating documents which
use namespace prefixes. Not sure about other parsers. This probably won't cause you
trouble, but if it does you may need to set validate=false to work around it. Contact the
author if this seems to be a serious issue for you.

OPTIONS

votable=<location>
Location of the VOTable to be checked. This may be a filename, URL or "-" (the
default), to indicate standard input. The input may be compressed using one of the
known compression formats (Unix compress, gzip or bzip2).

ucd=true|false
If true, the ucd attributes on FIELD and PARAM elements etc are checked for
conformance against the UCD1+ standard or a list of known UCD1 terms.

unit=true|false
If true, the unit attributes on FIELD and PARAM elements are checked for
conformance against the VOUnits standard; if false, no such checks are made.

The VOTable 1.4 standard recommends use of VOUnits, though there are some
inconsistencies in the text on this topic. Earlier VOTable versions refer to a
different (CDS) unit syntax, which is not checked by votlint. So by default unit
syntax is checked when the VOTable is 1.4 or greater, and not for earlier versions,
but that can be overridden by giving a true or false value for this parameter.

The wording of the VOTable and VOUnit standards do not strictly require use of
VOUnit syntax even at VOTable 1.4, so failed checks result in Warning rather than
Error reports.

maxrepeat=<int-value>
Puts a limit on the number of times that the same issue will be reported. With this
set to a relatively small number, the output is not cluttered with many repetitions
of the same problem.

validate=true|false
Whether to validate the input document aganist the VOTable DTD. If true (the
default), then as well as votlint's own checks, it is validated against an
appropriate version of the VOTable DTD which picks up such things as the presence
of unknown elements and attributes, elements in the wrong place, and so on.
Sometimes however, particularly when XML namespaces are involved, the validator can
get confused and may produce a lot of spurious errors. Setting this flag false
prevents this validation step so that only votlint's own checks are performed. In
this case many violations of the VOTable standard concerning document structure
will go unnoticed.

version=1.0|1.1|1.2|1.3|1.4
Selects the version of the VOTable standard which the input table is supposed to
exemplify. The version may also be specified within the document using the
"version" attribute of the document's VOTABLE element; if it is and it conflicts
with the value specified by this flag, a warning is issued.

If no value is provided for this parameter (the default), the version will be
determined from the VOTable itself.

out=<location>
Destination file for output messages. May be a filename or "-" to indicate standard
output.

VERSION

       STILTS version 3.4.6-debian

       This  is  the  Debian  version  of Stilts, which lack the support of some file formats and
       network protocols. For differences see
       file:///usr/share/doc/stilts/README.Debian

AUTHOR