Exactly one of uri, file or string must be given. Validation is then performed by using the W3C Markup Validation
service at the given URL, using the (still declared
experimental) SOAP 1.2 API of such a service (see
http://validator.w3.org/docs/api.html for more information).
If a SOAP validation response could be obtained,
w3c_markup_validate() returns the information in the response
organized into an object of class "w3c_markup_validate", which
is a list with the following elements:
valid- a logical indicating the validity of the web
document checked (TRUE iff there were no errors)
errorcountan integer giving the number of errors
found.
errorsa data frame with variables line,
col, message, messageid,
explanation and source with the obvious
meanings, or NULL.
warningcountan integer giving the number of warnings
found.
warningsa data frame with variables as for
errors, or NULL.
This class has methods for print for compactly
summarizing the results, an inspect method for inspecting
details, and an as.data.frame method for collapsing the
errors and warnings into a flat data frame useful for further
analyses.