\name{parseVar}
\alias{parseVar}
\alias{xmlDiscreteVariable}
\alias{xmlReportingVar}
\alias{xmlObservable}
\title{Translates varDescription objects to/from StatShop XML}
\usage{ 
parseVar(xNode)
xmlDiscreteVariable(var)
xmlReportingVar(var)
xmlObservable(obs)
}

\arguments{
  \item{xNode}{\code{XMLNode} corresponding to a
    \code{<DiscreteVariable>} element.}
  \item{var}{A \code{varDescription} object to be output.}
  \item{obs}{A \code{varDescription} object to be output.}
}
\description{
  The function \code{parseVar} decodes an \code{<DiscreteVariable>}
  XMLNode and produces a \code{varDescription} object.

  The function \code{xmlDiscreteVariable} does the opposite.

  The function \code{xmlReportingVar} creates a reference to the
  reporting variable for use in student models.  The function
  \code{xmlObservable} creates the reference for evidence/link models.
}
\value{
  A \code{varDescription} or \code{XMLNode} object containing the same
  information as the argument.
}
\details{
  The \code{parseVar} and \code{xmlVarDescription} functions are for use
  in reading/constructing GM files.  The others are for use with AMD
  files.  

  The function \code{xmlObservable} actually writes out one of three
  elements according to the following rules:
  \itemize{
    \item{}{If the \code{isOrdered} field has the value \code{TRUE}, then
      the tag  used is \code{<OrderedObservable>}.}
    \item{}{If the \code{isOrdered} field has the value \code{FALSE}, and
      the variable has exactly two states then
      the tag  used is \code{<LogicalObservable>}.}
    \item{}{Otherwise, the tag used is \code{<UnorderedObservable>}.}
    }

}
\section{Under Construction}{
  Currently the true state information is ignored.  On output it is
  assumed that all but the last state in the list is \dQuote{true}.
}
\references{
  \url{http://research.ets.org/~ralmond/StatShop/dataFormats.html}
}
\seealso{
  \code{\link[XML]{XMLNode}}, \code{\link{varDescription}},
  \code{\link{getEMParametersForAMD}},\code{\link{getLMParametersForAMD}}
  \code{\link{amdToPD}}, \code{\link{xmlStudentModel}},
  \code{\link{xmlEvidenceModelSet}}
}
\examples{
  skill1 <- varDescription("Skill1","Skill 1", "SM",
                           c("High","Medium","Low"),TRUE)
  sk1node <- xmlDiscreteVariable(skill1)
  sk1vd <- parseVar(sk1node)
  \dontshow{
    stopifnot(identical(skill1,sk1vd))
  }

  sk1rv <- xmlReportingVar(skill1)
  \dontshow{
    stopifnot(identical(sk1rv[["name"]],sk1node[["externalName"]]),
              identical(sk1rv[["varName"]],sk1node[["nodeName"]]),
              identical(xmlName(sk1rv),"ReportingVar"))
  }
  oo1 <- varDescription("Grade","Grade", "Observable",
                           c("A","B","C","D","E"),TRUE)
  oonode <- xmlObservable(oo1)
  lo1 <- varDescription("isCorrect","is Correct",
                         "Observable", c("Correct","Incorrect"),FALSE)
  lonode <- xmlObservable(lo1)
  uo1 <- varDescription("Approach","Approach",
                        "Observable", c("MethodA","MethodB","Other"),FALSE)
  uonode <- xmlObservable(uo1)

  \dontshow{
   stopifnot(
    identical(xmlName(oonode),"OrderedObservable"),
    identical(xmlName(lonode),"LogicalObservable"),
    identical(xmlName(uonode),"UnorderedObservable"),
    all(sapply(xmlElementsByTagName(oonode,"State"),xmlValue) == oo1$levels),
    all(sapply(xmlElementsByTagName(lonode,"State"),xmlValue) == lo1$levels),
    all(sapply(xmlElementsByTagName(uonode,"State"),xmlValue) == uo1$levels)
   )
  }

}
\keyword{interface}