I've been working on this one for a while, and have finally given up.

I have currently 2 different filters i'd like to apply to my xpath query. one is a time based one (month & year), and another is a category query. My goal is to create either different queries and intersect them to get common elements, or to build a smart query (not preferred) which will only set my attribute filters if they are set.

I've been messing around with some examples i've found using set:intersection and $n1[count(.|$n2) = count($n2)] and i'm either doing it wrong (most likely) or it's not working.

here's what i was doing regarding the intersection

<xsl:variable
 name="month" select="/macro/month" />
<xsl:variable name="year" select="/macro/year" />
<xsl:variable name="categoryId"
 select="/macro/categoryId"
 />

<xsl:variable
 name="timeQuery">
  <xsl:choose>
    <xsl:when test="$year!='' and $month!=''">
        <xsl:copy-of
 select="$currentPage/Posts/Year[@nodeName=$year]/Month[@nodeName=$month]/*"/>      
 
   </xsl:when>
    <xsl:when test="$year!=''">
      
  <xsl:copy-of select="$currentPage/Posts/Year[@nodeName=$year]/Month/*"/>
    </xsl:when>
    <xsl:when test="$month!=''">
        <xsl:copy-of select="$currentPage/Posts/Year/Month[@nodeName=$month]/*"/>
    </xsl:when>
    <xsl:otherwise>
      
  <xsl:copy-of select="$currentPage/Posts/Year/Month/*"/>
    </xsl:otherwise>
  </xsl:choose>    
</xsl:variable> 
    
<xsl:variable
 name="categoryQuery">  
    <xsl:if test="$categoryId!=''">
      <xsl:copy-of
 select="$currentPage/Posts/Year/Month/*[category[text()=$categoryId]]"/>      
 
   </xsl:if>  
</xsl:variable> 
    
<xsl:variable
 name="intersection"
 select="msxml:node-set($timeQuery)[count(.|msxml:node-set($categoryQuery))
 = count(msxml:node-set($categoryQuery))]" />

<xsl:template
 match="/">   
  <ul>
    <xsl:for-each
 select="$intersection">.....

i took a quick stab at a smart query, using if else conditionals (which i found was in xpath 2.0), but i guess i was doing it wrong, as i continued to get errors on the if() being invalid.

<xsl:variable name="query" select="$currentPage/Posts/Year if($year!='') then([@nodeName=$year])/Month if($month!='') then([@nodeName=$month])/* if($categoryId!='') then([category[text()=$categoryId]])"/> 

Thanks for any input!