$ awk -F'[<>]' 'BEGIN{F="\t<si><t>";B="</t></si>";H="Report,Tittle,Number,Address,Date,Description"; split(H, arrH, /,/);
  for (i=1;i<=length(arrH);i++) { printf "%s%s%s\n", F, arrH[i], B} }
    NR==FNR{
    if ($2~"file title") { split ($0,N,"\""); print F N[2] B } else if (\
    $2=="title" || $2=="number" || $2=="address" || $2=="date" || $2=="description" ) {print F $3 B}
    next} 
    $2 ~ /f v=\"/{u[$3]}
    END{for (i in u) print F i B | "sort"}' file1 file2
        <si><t>Report</t></si>
        <si><t>Tittle</t></si>
        <si><t>Number</t></si>
        <si><t>Address</t></si>
        <si><t>Date</t></si>
        <si><t>Description</t></si>
        <si><t>Title 1 and 2</t></si>
        <si><t>Title 1</t></si>
        <si><t>No. 1234</t></si>
        <si><t>Address 1</t></si>
        <si><t>October 07, 2009</t></si>
        <si><t>Some text</t></si>
        <si><t>Title 2</t></si>
        <si><t>No. 457</t></si>
        <si><t>Address 2</t></si>
        <si><t>October 15, 2009</t></si>
        <si><t>Some text</t></si>
        <si><t>Report o</t></si>
        <si><t>Report t</t></si>
        <si><t>Report u</t></si>
        <si><t>Report x</t></si>
        <si><t>Report y</t></si>