swh:1:snp:7d9f1bc35e120776766db9334626062f837c20ad
Tip revision: db230f20006a0b7edc98fff17930bcdba29e22dd authored by Duncan Temple Lang on 21 July 2008, 00:00:00 UTC
version 1.96-0
version 1.96-0
Tip revision: db230f2
catalogResolve.Rd
\name{catalogResolve}
\alias{catalogResolve}
\title{Look up an element via the XML catalog mechanism}
\description{
XML parsers use a catalog to map generic system and public addresses
to actual local files or potentially different remote files.
We can use a catalog to map a reference such as
\code{http://www.omegahat.org/XSL/} to a particular
directory on our local machine and then not have to
modify any of the documents if we move the local files to another
directory, e.g. install a new version in an alternate directory.
This function provides a mechanism to query the catalog to
resolve a URI, PUBLIC or SYSTEM identifier.
This is now vectorized, so accepts a character vector of
URIs and recycles \code{type} to have the same length.
If an entry is not resolved via the catalog system,
a \code{NA} is returned for that element.
To leave the value unaltered in this case, use \code{asIs = TRUE} .
}
\usage{
catalogResolve(id, type = "uri", asIs = FALSE, debug = FALSE)
}
%- maybe also 'usage' for other objects documented here.
\arguments{
\item{id}{the name of the (generic) element to be resolved}
\item{type}{a string, specifying whether the lookup is for a uri,
system or public element}
\item{asIs}{a logical. If \code{TRUE} any element of \code{id} which
is not resolved by the catalog system will be left as given in the
call. If \code{FALSE}, such unresolved elements are identified
by \code{NA}.
}
\item{debug}{logical value indicating whether to turn on debugging
output written to the console (\code{TRUE}) or not (\code{FALSE}).}
}
\value{
A character vector. If the element was resolved,
the single element is the resolved value.
Otherwise, the character vector will contain no elements.
}
\references{
\url{http://www.xmlsoft.org}
\url{http://www.sagehill.net/docbookxsl/Catalogs.html} provides a short, succinct tutorial on catalogs.
}
\author{Duncan Temple Lang}
\seealso{
\code{\link{xmlTreeParse}}
}
\examples{
if(!exists("Sys.setenv")) Sys.setenv = Sys.putenv
Sys.setenv("XML_CATALOG_FILES" = system.file("exampleData", "catalog.xml", package = "XML"))
catalogResolve("-//OASIS//DTD DocBook XML V4.4//EN", "public")
catalogResolve("http://www.omegahat.org/XSL/foo.xsl")
catalogResolve("http://www.omegahat.org/XSL/article.xsl", "uri")
catalogResolve("http://www.omegahat.org/XSL/math.xsl", "uri")
# This one does not resolve anything, returning an empty value.
catalogResolve("http://www.oasis-open.org/docbook/xml/4.1.2/foo.xsl", "uri")
# Vectorized and returns NA for the first and /tmp/html.xsl
# for the second.
catalogAdd("http://made.up.domain", "/tmp")
catalogResolve(c("ddas", "http://made.up.domain/html.xsl"), asIs = TRUE)
}
\keyword{IO}
\concept{XML}