<patents>
      <patent patno="101103062330">
        <office coden="EPO"  short="Eur. Pat. Office"> European Office    </office>
        <volume>80    </volume>
        <issue printdate="2009-12-00">6    </issue>
        <numpages>13    </numpages>
        <section code="A-2D"> Filtering    </section>
        <patno>101103062330    </patno>
        <title> trapping plastic waste    </title>
        <authgrp>
          <author>
            <givenname>Endo    </givenname>
            <surname>Wake    </surname>
          </author>
          <author>
            <givenname>C.    </givenname>
            <surname>Morde    </surname>
          </author>
          <aff> University of M, USA    </aff>
        </authgrp>
        <history>
          <received date="2009-07-01"/>
          <published date="2009-07-30"/>
        </history>
        <tag tagyr="2009">
          <tagcode>B1.C2.B5    </tagcode>
          <tagcode>F4.65.F6    </tagcode>
        </tag>
        <assignment>
          <assigndate date="2009"/>
          <rightholder> university of M    </rightholder>
        </assignment>
  </patent>
      <patent patno="101103062514">
        <office coden="EPO"  short="Eur. Pat. Office"> European Office    </office>
        <issue printdate="2009-12-00">6    </issue>
        <numpages>15    </numpages>
        <section code="A-3D"> structure and dynamics    </section>
        <patno>101103062514    </patno>
        <title> separation of cascades and photon emission    </title>
        <authgrp>
          <author affref="a1 a2">
            <givenname>L.    </givenname>
            <surname>Slabsky    </surname>
          </author>
          <author affref="a1">
            <givenname>D.    </givenname>
            <surname>Volosvyev    </surname>
          </author>
          <author affref="a3">
            <givenname>G.    </givenname>
            <surname>Nonpl    </surname>
          </author>
          <aff affid="a1"> Institute of Physics,Russia    </aff>
          <aff affid="a2"> Physics Institute, St. Petersburg     </aff>
          <aff affid="a3">Technische Universiteit, Dresden    </aff>
        </authgrp>
        <history>
          <received date="2009-01-11"/>
          <published date="2009-01-31"/>
        </history>
        <tag tagyr="2009">
          <tagcode>A1.B2.C3    </tagcode>
        </tag>
        <assignment>
          <assigndate date="2009"/>
          <rightholder> Physics Inst    </rightholder>
        </assignment>
  </patent>
</patents>

`Patent Author1 Author2 Author3
101103062330 Endo Wake  C. Morde
101103062514 L. Slabsky D.Volosyev  G. Nonpl`

`Patent Author
    101103062330 Endo Wake
    101103062330 C. Morde
    101103062514  L. Slabsky
    101103062514  D.Volosyev
    101103062514  G. Nonpl`

`Patent Tag
    101103062330 B1.C2.B5
    101103062330 F4.65.F6
    101103062514 A1.B2.C3`

`Author  Institution
    Endo Wake   University of M
    C. Morde        University of M
    L. Slabsky      Institute of Physics,Russia
    D.Volosyev  Physics Institute, St. Petersburg
    G. Nonpl        Technische Universiteit, Dresden`

xmlfile     <- xmlInternalTreeParse("filename.xml", useInternal = T)
nodes     <- getNodeSet(xmlfile, "//patent")
authors     <- lapply(nodes, xpathSApply, ".//author", xmlValue)
patent     <- sapply(nodes, xpathSApply, ".//patent", xmlValue)

dt1 <- ldply(xmlToList(xmlfile), data.table)

lapply(
  getNodeSet(patents, "//patent"),
  function(patent){
    data.frame(
      patent = xmlAttrs( patent )[["patno"]],
      xmlToDataFrame(
        nodes = getNodeSet(patent,".//*[contains(local-name(), 'author')]")
      ),
      stringsAsFactors = FALSE
    )
  }
)

lapply(
  getNodeSet(patents, "//patent"),
  function(patent){
    data.frame(
      patent = xmlAttrs( patent )[["patno"]],
      tag = xpathSApply(
        patent,
        ".//tagcode",
        xmlValue
      ),
      stringsAsFactors = FALSE
    )
  }
)

lapply(
  getNodeSet(patents, "//authgrp"),
  function(autg){
    aff_df <- do.call(
      rbind,
      xpathApply(
        autg,
        ".//aff[@affid]",  # get only those with affid attr
        function(aff){
          data.frame(
            aff_id = xmlAttrs(aff)[["affid"]],
            institution = xmlValue(aff)
          )
        }
      )
    )

    authors <- getNodeSet( autg, "./author")
    aut_df <- xmlToDataFrame( nodes = authors )
    aut_df$aff_id <- lapply(
      1:length(authors)
      ,function(i){
        if(!is.null(xmlAttrs(authors[[i]])[["affref"]])){
          xmlAttrs(authors[[i]])[["affref"]]
        } else {
          NA
        }
      }
    )

    list(aff_df,aut_df)
  }
)