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### B.49.2 Items Checked

Votlint checks that the XML input is well-formed, and, unless the `valid=false` parameter is supplied, that it validates against the 1.0 DTD or 1.1, 1.2, 1.3, 1.4, 1.5 or 1.6 schema as appropriate. Some of the validity checks are also done by `votlint` internally, so that some validity-type errors may give rise to more than one warning. In general, the program errs on the side of verbosity.

In addition to these checks, the following checks are carried out, and lead to ERROR reports if violations are found:

- `TD` contents incompatible with `datatype`/`arraysize` attributes declared in `FIELD`
- BINARY/BINARY2 data streams which don't match metadata declared in `FIELD`
- `PARAM` values incompatible with declared `datatype`/`arraysize`
- Meaningless `arraysize` declarations
- Array-valued `TD` elements with the wrong number of elements
- Array-valued `PARAM` values with the wrong number of elements
- `nrows` attribute on `TABLE` element different from the number of rows actually in the table
- `VOTABLE` `version` attribute is unknown
- `ref` attributes without matching `ID` elements elsewhere in the document
- Same `ID` attribute value on multiple elements.
- Attributes defined by external vocabularies have permitted values; hard-coded lists of known permitted values are stored internally, but the external vocabularies are consulted if necessary to check for values added after build time (currently only applies to `TIMESYS` attributes).
- Values marked by `xtype` values as defined in DALI are checked for formal compliance with DALI requirements.

Additionally, the following conditions, which are not actually forbidden by the VOTable standard, will generate WARNING reports. Some of these may result from harmless constructions, but it is wise at least to take a look at the input which caused them:

- Wrong number of `TD` elements in row of `TABLEDATA` table
- Mismatch between VOTable and FITS column metadata for FITS data encoding
- `TABLE` with no `FIELD` elements
- Use of deprecated attributes
- `FIELD` or `PARAM` elements with `datatype` of either `char` or `unicodeChar` and undeclared `arraysize` - this is a common error which can result in ignoring all but the first character in `TD` elements from a column
- `ref` attributes which reference other elements by `ID` where the reference makes no, or questionable sense (e.g. `FIELDref` references `FIELD` in a different table)
- Multiple sibling elements (such as `FIELD`s, though not `INFO`s) with the same `name` attributes
- `TIMESYS` elements never referenced.
- `ucd` attribute values are not legal UCD1+ strings (if parameter `ucd=true`)
- `unit` attribute values are not legal VOUnit strings (if parameter `unit=true`)

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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk