Re: "castable as" explanation

On Monday 28 August 2006 14:48, cknell@xxxxxxxxxx wrote:
> I'm using Saxon 8.7.1J.
>
> I have output from a database in the form of an XML document that I
> transform using XSLT. As an expediant, the persons in responsible positions
> decided to encode data in a text field in order to accomplish a goal rather
> than wait until the application and database are upgraded.
>
> Some records will contain this "packed" information and others will not. I
> need to determine if an element in the output XML document contains the
> packed information or does not, and process each type differently.
>
> One of the data items packed into this text field is a date. I have
> substringed the text so as to construct a date (YYYY-MM-DD) if there is
> indeed a date encoded in the field.
>
> I thought to use "castable as" in order to distinguish between those fields
> containing the packed information and those that do not. Here the relevant
> section of my stylesheet:
>
> <xsl:variable name="is-date" select="if(DATE_PACKED_XSD castable as
> xs:date) then '1' else('0')" />
>
> <xsl:choose>
>   <xsl:when test="$is-date = '1'">
>     ... some processing here
>   </xsl:when>
>   <xsl:otherwise>
>     ... some different processing here
>   </xsl:otherwise>
> </xsl:choose>

If a variable is treated as a boolean value, let it be a boolean value. That 
is:

<xsl:variable as="xs:boolean" name="is-date" select="(DATE_PACKED_XSD castable 
as xs:date"/>

<xsl:choose>
 <xsl:when test="$is-date">
	....

The 'as="xs:boolean"' is not strictly necessary, but it makes your code safer 
and more readable, some would say.

> What I expected to happen was that when the stylesheet processed a
> DATE_PACKED_XSD element that could not be cast as a date ($is-date = 0),
> processing would pass to the <xsl:otherwise> branch.
>
> What did happen was this:
>
> stylesheet.xslt:423: Fatal Error! Invalid date "208 2-01-1 2". Non-numeric
> component
>
> What am I misapprehending about "castable as"?

Nothing about 'castable as', but "208 2-01-1 2" simply isn't a valid date. A 
valid text representation for a date is for example "2082-01-12". If you need 
to read dates in some custom format, you will need to text process those 
strings first such that they are valid xs:dateS. Here's the detailed 
description of xs:date:

http://www.w3.org/TR/xmlschema-2/datatypes.html#date


Cheers,

		Frans