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## B.24 `taplint`: Tests TAP services

`taplint` runs a series of tests on a Table Access Protocol (TAP) service and reports the results. Unlike most of the other tools in this package it is not likely to be of use to normal users; its intended use is for people developing or operating TAP services to assess their services, perhaps with a view to improving compliance.

Testing takes place in a number of stages; it is possible to choose which stages are run in by using the `stages` parameter. The default output (`format=text`) is line-based text to standard output, and each report line is of the (fairly greppable) form:

       T-SSS-MMMMxN aaaaa...

where the parts have the following meanings:

- `T`: Report type, one of E(rror), W(arning), I(nfo), S(ummary), F(ailure). See the documentation of the `report` parameter for further description of what these mean. The `report` parameter can be used to suppress some of these; only `E` indicates actual service compliance errors, but including the others may make it easier to see what's going on.
- `SSS`: Stage abbreviation, as used in the `stages` parameter. The `stages` parameter can be used to select which stages are run.
- `MMMM`: Message label, which is always the same for messages generated by the same test, is usually different for messages generated by different tests, and may be somewhat mnemonic.
- `x`: Continuation indicator, either "`-`" or "`+`". In most cases it is "`-`", indicating the first line of a message, but multi-line messages (rare) use "`-`" for the first line and "`+`" for any continuation lines.
- `N`: Sequence number, which is 1 for the first time message `T-SSS-MMMM` is reported, and increases by one for each subsequent appearance. After a certain maximum (determined by the `maxrepeat` parameter) additional reports with the same code are no longer output individually, but a summary of the number of reports so discarded is written at the end of the section with the character "`x`" instead of the sequence number. This behaviour prevents the output being swamped by multiple reports of the same issue. If the `maxrepeat` parameter is increased above 9, more than one digit will be used here (so e.g. for maxrepeat=999, the format would be `NNN` not `N`).
- `aaaaa...`: Message text, a free text description of what is being reported.

If you don't like that format, others may be selected using the `format` parameter, which currently also supports JSON. For more flexible interaction with the output you can invoke `taplint` programmatically and supply your own `OutputReporter` instance.

TAP is a complicated beast, referencing many standards (including TAP, UWS, VODataService, ADQL, VOResource, VOSI, TAPRegExt, DALI, ObsCore, ObsLocTAP, EPN-TAP, VOTable, UCD, VOUnits, SSO, SoftID, HTTP, RDFa Lite), and it is hard to write a validator which is comprehensive, especially one which can provide useful output for services with a range of compliance levels. This tool tries to make a wide range of tests, but does not claim to be comprehensive. An idea of what tests it does perform can be gained from the stages listed in the description of the `stages` parameter. It does make a fairly good job of checking that declared metadata is consistent and matches the data actually returned from queries, it tests job submission in most of the various ways permitted by the TAP standard, and it checks all returned VOTables by effectively running them through `votlint`. Things it does not test much include complex ADQL queries, coordinate/STC-related data types, queries in non-ADQL languages, and service registration.

HTTP connections made by this validator are flagged in the `User-Agent` field with the token "`(IVOA-test)`".

- B.24.1 Usage
- B.24.2 Examples

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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