Question

I have a XML file that display the pubblications from an author with some article or inproceeding node. Something like this:

<dblp>
<inproceedings key="aaa" mdate="bbb">
<author>author1</author>
<author>author2</author>
<author>author3</author>
<author>author4</author>
<title>Title of pubblications</title>
<pages>12345</pages>
<year>12345</year>
<crossref>sometext</crossref>
<booktitle>sometext</booktitle>
<url>sometext</url>
<ee>sometext</ee>
</inproceedings>

<article key="aaa" mdate="bbb">
<author>author1</author>
<author>author2</author>
<title>Title of pubblications</title>
<pages>12345</pages>
<year>12345</year>
<crossref>sometext</crossref>
<booktitle>sometext</booktitle>
<url>sometext</url>
<ee>sometext</ee>
</article>

</dblp>

I have to create an XSL stylesheet to trasform this file in a .dot file that shows only the collaboration with the authors from all the pubblications. Like this:

author1--author2;
author1--author3;
author1--author4;
author2--author3;
author2--author4;
author3--author4;

This for the first pubblication and this for the second:

author1--author2;

I have to write all the connection by the author with no repeats. How can i do this?
I write something to display all the connection but i must delete the repeats. Can i solve using following-sibling?

<xsl:variable name="papers" select="dblp/*"/>
        <xsl:for-each select="$papers">
            <xsl:variable name="autori" select="author"/>
            <xsl:variable name="autori2" select="author"/>
            <xsl:for-each select="$autori">
                <xsl:variable name="i" select="node()"/>
                    <xsl:for-each select="$autori2">
                        <xsl:if test=".!=$i">
                            <xsl:value-of select="$i"/><xsl:text>--</xsl:text><xsl:value-of select="."/><xsl:text>;</xsl:text>
                        </xsl:if>
                    </xsl:for-each><xsl:text>&#xa;</xsl:text>
            </xsl:for-each>
        </xsl:for-each>

Thanks for the answers!

Answer 1

<xsl:for-each select="author[position() != last()]">
  <xsl:variable name="a1" select="."/>
  <xsl:for-each select="following-sibling::author">
    <xsl:value-of select="concat($a1, '--', ., ';&#10;')"/>
  </xsl:for-each>
</xsl:for-each>