[xsl] constructing an element with an element's content based on the content of sibling element

[Dana Pearson <dbpearsonmlis@xxxxxxxxx>]

Greetings,

Hoping someone can point out my misunderstanding of the solution in my
transformation to the construction of an element, <controlfield>, with
a preferred ISBN and the use of a second ISBN (13 characters vs. 10)
if the preferred is unavailable; otherwise, nothing.

<productidentifier>
 <b221>02</b221>
 <b244>160542868X</b244>
</productidentifier>
<productidentifier>
 <b221>03</b221>
 <b244>9781605428680</b244>
</productidentifier>
<productidentifier>
 <b221>15</b221>
 <b244>9781605428680</b244>
</productidentifier>

All of the product records have 3 productidentifiers with b221 element
values in the following order: 02, 03, 15.

To test the element construction with the second ISBN (b221=02) if the
preferred ISBN (b221=15) is missing, I removed the productidentifer
with element b221=15 from the second product record; I removed all
productidentifiers from the third record.

<xsl:for-each select="productidentifier">
  <xsl:variable name="isbn13">
    <xsl:choose>
	 <xsl:when test="b221='15'">
	   <xsl:value-of select="b244"/>
	 </xsl:when>
	 <xsl:otherwise></xsl:otherwise>
    </xsl:choose>
  </xsl:variable>
  <xsl:variable name="isbn10">
    <xsl:choose>
	 <xsl:when test="b221='02'">
	   <xsl:value-of select="b244"/>
	 </xsl:when>
	 <xsl:otherwise></xsl:otherwise>
    </xsl:choose>
   </xsl:variable>
			
   <xsl:choose>
	<xsl:when test="not(empty($isbn13))">
	  <controlfield tag="001">
	  <xsl:text>xyz</xsl:text><xsl:value-of select="$isbn13"/>
	  </controlfield>
	</xsl:when>
	<xsl:otherwise></xsl:otherwise>
   </xsl:choose>

   <xsl:choose>
	<xsl:when test="empty($isbn13)">
	  <controlfield tag="001">
	  <xsl:text>xyz</xsl:text><xsl:value-of select="$isbn10"/>
	  </controlfield>
	</xsl:when>
	<xsl:otherwise></xsl:otherwise>
   </xsl:choose>

</xsl:for-each>

The results of  the three records:

record 1

    <controlfield tag="001">xyz</controlfield>
    <controlfield tag="001">xyz</controlfield>
    <controlfield tag="001">xyz9781605428680</controlfield>

record 2

    <controlfield tag="001">xyz</controlfield>
    <controlfield tag="001">xyz</controlfield>

record 3 has the desired result of no controlfield tag=001

I am apparently not accounting for productidentifier/b221=03 but have
tried creating a similar variable which would result in an empty
string...have tried using exists()...not using variables...but always
get the same result..

hope the problem is clear...a little cross-eyed at this point..

any help would be greatly appreciated...

regards,
dana

-- 
Dana Pearson
dbpearsonmlis.com