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\title{Generating an organized set of links to pubmed items}
\author{VJ Carey}
\maketitle

\section{Introduction}

I want to have a relatively flat but hierarchical
presentation of links to published literature.
My criterion for linkable publication is existence
of a pubmed id; this can be made more general in the future.

An example of what I want is at
\url{http://www.biostat.harvard.edu/~carey/provref08.html}.

To create this, I work from a hierarchical list in R.
The outermost named list enumerates topics.
Each element of the topic list has a named list of subtopics.
Each subtopic has a vector of character pubmed IDs.

The remaining sections of this document show how to
create relevant objects and methods for serialization
to HTML.  It was convenient to use Pau's hwriter package to do this.

\section{The URL for the pubmed abstract page corresponding
to a PMID}


The workhorse URL generator is:
<<doit>>=
options(width=55)
mkURL = function(
   id="12584122",
   pre = "http://www.ncbi.nlm.nih.gov/pubmed/",
   post="?ordinalpos=9&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum") {
 paste(pre, id, post, sep="")
}
@

If we execute this, we get:
<<doit2>>=
ur = mkURL()
ur
@
This string can be passed to \texttt{browseURL} for immediate
inspection, but we want to create an organized web page
that includes the generated links.

\section{A reference object}

We propose an object structure that encodes the organization.
<<docl>>=
setClass("litRef", representation(topic="character",
   subtopic="character", pmid="character"))
mkLitRef = function(topic, subtopic, pmid) {
  new("litRef", topic=topic, subtopic=subtopic, pmid=pmid)
}
setMethod("show", "litRef", function(object) {
 cat("pubmed ref: pmid ", object@pmid, "\n")
 cat("topic: ", object@topic, "\n")
})
ex = mkLitRef("Multiple testing", "FDR/microarray", "12584122")
ex
@

That's  perhaps a minimally sufficient schema.  Now we want to
use the web to populate some additional fields to make
the report useful.

\section{Using the pubmed() XML response to get key fields}

First we define a function that extracts key information from
a pubmed xml query:
<<getk>>=
pmidKeyData = function (pmid="12584122", maxauth=3)
{
    require("XML") || stop("need the XML package for this function")
    x = pubmed(pmid)
    rr = xmlRoot(x)
    top = xmlChildren(rr)
    pmart = top[["PubmedArticle"]]
    cit = xmlChildren(pmart)[["MedlineCitation"]]
    art = cit[["Article"]]
    cart = xmlChildren(art)
    yr = xmlValue(xmlChildren(
        xmlChildren(xmlChildren(cart[["Journal"]])$JournalIssue)$PubDate)$Year)
    tmp = lapply(xmlChildren(cart$AuthorList), xmlChildren)
    al = sapply(tmp, function(x) xmlValue(x$LastName))
    if (length(al)>3) al = c(al[1:3], "et al.")
    journalTitle = try(xmlValue(xmlChildren(cart$Journal)$ISOAbbreviation), silent=TRUE)
    if (inherits(journalTitle, "try-error"))
        journalTitle = try(xmlValue(xmlChildren(cart$Journal)$Title))
    list(journalTitle = journalTitle,
    articleTitle = xmlValue(cart$ArticleTitle),
    authorList = paste(al, collapse=", "), year=yr)
    #cart=cart)
}
@

\section{A richer 'entry' object}

Now we use this to populate the enriched entry:

<<domore>>=
setClass("litEntry", representation(auth="character",
 title="character", journal="character", year="character"),
 contains="litRef")
setGeneric("makeEntry", function(lr) standardGeneric("makeEntry"))
setMethod("makeEntry", "litRef", function(lr) {
 require(annotate)
 x = pmidKeyData(lr@pmid)
 new("litEntry", auth=x$authorList, title=x$articleTitle,
    journal=x$journalTitle, year=x$year, lr)
})
setMethod("show", "litEntry", function(object) {
 cat("literature entry:\n")
 callNextMethod()
 cat("  title: ", object@title)
 cat("\n")
 cat("  journal: ", object@journal, "(", object@year, ")\n")
})
ddd = makeEntry(ex)
ddd
@

\section{An example schema (list) for a page}

To specify the page to be generated, we use a hierarchical
list.

<<myl>>=
mylit = list()
topics = c("Cautions", "Yeast", "Expression arrays", "Protein-DNA arrays",
  "Expression plus genotyping", "Structural variation", "High-throughput sequencing",
  "Statistics", "Computing")
for (i in 1:length(topics)) mylit[[topics[i]]] = list()
mylit[["Cautions"]][["Irreproducibility"]] = c("17987014", "15814023")
mylit[["Cautions"]][["Batch effects"]] = c("17597765", "18309960")
mylit[["Yeast"]][["Cell cycle"]] = c("9843569", "12399584")
mylit[["Yeast"]][["Environmental stress response"]] = c("11102521")
mylit[["Yeast"]][["Species divergence of TFBS"]] = c("17690298")
mylit[["Yeast"]][["Transcriptional regulation"]] = c("17311525", "15113405")
mylit[["Yeast"]][["Post-transcriptional regulation"]] = c("16317069")
mylit[["Expression arrays"]][["Theory: absolute mRNA concentrations"]] = c("12655013")
mylit[["Expression arrays"]][["Application: Breast cancer/stem compendium"]] = c("18443585")
mylit[["Expression arrays"]][["Application: Pancreatic cancer/pathway addiction"]] = c("18413752")
mylit[["Protein-DNA arrays"]][["TF binding specificities"]] = c("16998473", "16839757")
mylit[["Protein-DNA arrays"]][["Harmen"]] = c("10812473")
mylit[["Expression plus genotyping"]][["Early work"]] = c("16251966", "17158513")
mylit[["Expression plus genotyping"]][["Multiple populations"]] = c("17206142", "17873874")
mylit[["Expression plus genotyping"]][["Drosophila"]] = c("17873888", "17418441")
mylit[["Structural variation"]][["Copy number: Breast cancer cell lines"]] = c("17157791")
mylit[["Structural variation"]][["Copy number: Glioma"]] = c("18077431")
mylit[["Structural variation"]][["Paired end mapping"]] = c("17901297")
mylit[["High-throughput sequencing"]][["Overview"]] = c("16339375", "18175411")
mylit[["High-throughput sequencing"]][["Impact"]] = c("18262675")
mylit[["Statistics"]][["Linear models"]] = c("16646809")
mylit[["Statistics"]][["Motif finding"]] = c("9719638", "11175784")
mylit[["Statistics"]][["Multiple testing"]] = c("12584122")
mylit[["Statistics"]][["GSEA"]] = c("16199517", "17903287", "17127676")
mylit[["Statistics"]][["Regularized LDA"]] = c("16603682")
mylit[["Computing"]][["Bioconductor"]] = c("15461798")
mylit[["Computing"]][["Reproducible research"]] = c("16646837")
@

\section{Walking the schema to generate the page}

We get a list of topics and subtopics as follows:
<<getto>>=
tops = lapply(mylit, names)
topics = names(tops)
@
We need to walk through this and create a list of litRef instances:
<<lkdd>>=
reflist = list()
for (i in 1:length(tops)) {
 reflist[[topics[i]]] = list()
 for (j in 1:length(tops[[i]])) # j is num subtopics
  reflist[[topics[i]]][[ tops[[i]][j] ]] = lapply(mylit[[i]][[j]],
      function(x) mkLitRef(topics[i], tops[[i]][j], x))
 }
entlist = lapply(reflist, lapply, lapply, makeEntry)
@

Now we need to be able to serialize entries to HTML.
We use the hwriter package.
<<newm>>=
setGeneric("HW", function(x,con) standardGeneric("HW"))
setMethod("HW", c("litEntry", "ANY"), function(x,con) {
 hwrite(x@title, con, link=mkURL(id=x@pmid), style="padding-left:30pt; font-family:sans-serif", br=TRUE)
 hwrite(x@auth, con, style="padding-left: 40pt; font-family:sans-serif")
 hwrite(", ", con)
 hwrite(x@journal, con, style="font-weight: bold; font-family:sans-serif")
 hwrite("(", con)
 hwrite(x@year, con, style="font-family:sans-serif")
 hwrite(")", con, br=TRUE)
})
 

@
The whole hierarchical structure is
then serialized to HTML using hwriter.
<<doh>>=
library(hwriter)
kk = openPage("demowrite.html", ".")
hwrite("A provisional set of references for preparation for CDATA-08", kk,
    style="font-weight: bold; font-size:130%; font-family:sans-serif", br=TRUE)
hwrite(" ", kk, br=TRUE)
tl = lapply(entlist, names)
for (i in 1:length(tl)) {
   hwrite(names(tl)[i], kk, style="font-weight: bold; font-size: 130%; font-family:sans-serif", br=TRUE)
   for (j in 1:length(tl[[i]])) {
     hwrite(tl[[i]][j], kk, style="padding-left:20pt; font-size: 115%; font-family:sans-serif", br=TRUE)
     for (k in 1:length(entlist[[i]][[j]]))
      HW(entlist[[i]][[j]][[k]], kk)
   }
 }
closePage(kk)
@

\section{Things to do}
\begin{itemize}
\item generalize to other kinds of links, such as doi or
direct URL specs ... the problem here is that we
may not get publishing metadata so easily and we probably
have to hand code author info, etc., ... but semantic web should eventually
solve that
\item meaningful links to software resources
\item combine with task view system
\end{itemize}

\end{document}
