RE: Assigning unique id to new node using generate-id()

If your code works, then it's working by luck.

If you define a key

  <xsl:key name="k" match="credential" use="@id"/>

then it's very easy to add a test

  <xsl:if test="not(key('k', generate-id())">

to check that the id you are generating is not the same as the id of an
element that you are copying. You can then try other IDs until you find
one that is indeed unique:

<xsl:template name="make-id">
  <xsl:param name="try"/>
  <xsl:choose>
    <xsl:when test="not(key('k', $try))">
      <xsl:value-of select="$try"/>
    </xsl:when>
    <xsl:otherwise>
      <xsl:call-template name="make-id">
        <xsl:with-param name="try" select="concat($try, 'ï')"/>
      </xsl:call-template>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>

The letter ï ('i' with two dots, in case the email service loses it) is
chosen here as a character that can appear in an ID attribute but that
cannot appear in the result of generate-id() (which is always ASCII). In
your initial call of this template, supply generate-id() as the first
try. If this is "G123", then this value will be used unless there is an
@id with value "G123"; if this happens the next try will be "G123ï", and
so on.

Michael Kay

-----Original Message-----
From: owner-xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com 
[mailto:owner-xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com] On Behalf Of 
kyle(_dot_)himmerick(_at_)insatiabit(_dot_)com
Sent: 13 August 2003 19:41
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: Re: [xsl] Assigning unique id to new node using generate-id()

Thank you for you reply.

I would like to keep the existing ID's the same.  As they are 
referenced from other nodes (a credential is referenced from 
0 or more services).

My current workaround seems to be working although I'm not 
100% convinced that it will always create a unique id.

After new node is created without an id, I transform the 
document again with. 
This is run against the result of the first transform which 
adds the new credential without and id.

<xsl:for-each select="credential">
      <xsl:choose>
              <xsl:when test="@id">
                      <xsl:copy-of select="."/>               

              </xsl:when>
              <xsl:otherwise>
                      <credential>
                              <xsl:attribute name="id">
                                      <xsl:value-of 
select="generate-id()"/>
                              </xsl:attribute>
                              <xsl:copy-of select="username"/>
                              <xsl:copy-of select="password"/>
                              <xsl:copy-of select="description"/>
                              <xsl:copy-of select="lastModified"/>
                      </credential>
              </xsl:otherwise>
      </xsl:choose>
</xsl:for-each>

As I said, this seems to work.

What other methods would you recommend for generating a 
unique id?  It is possible, albeit unlikely, that the a 
profile may contain identical credential nodes (where 
username, password, description and lastModified are identical).

Thanks,
Kyle

On Wed, 13 Aug 2003 13:10 , Wendell Piez 
<wapiez(_at_)mulberrytech(_dot_)com> sent:

Hi Kyle,

At 12:11 PM 8/13/2003, you wrote:

I'd like this stylesheet to copy all existing credential nodes and 
create
a new
node assigning a unique id


It's a reasonable requirement.

 with generate-id().


Why? as opposed to by some other means?

  It appears as if the generate-id
call doesn't observe existing id's in the current/copied credential
nodes.  So I
end up with duplicate (illegal) id's.  I've tried passing

several context

nodes
to the generate-id() function, but with no luck.

Sample XSL:
        
                
                        
                                
                        
                        
                                
                                        
select="generate-id()"/>
                                
                                
select="$username"/>
                                
select="$password"/>
                                
select="$description"/>
                                
select="java:getCurrentDateTimeGMT($dateHelper)"/>
                        
                
        

My current workaround is to transform twice.  The first

transformation

appends the new credential node.  The second transformation

assigns an

id (using
generate-id()) to any credential nodes without an id

(probably only newly

created).  Seems like I should be able to do it all in one

transform.


The root of your problem is in thinking that generate-id() assigns 
(unique)
IDs to new nodes, when it doesn't; it merely assigns (or

retrieves) an ID

for a node in the source. The generated value has nothing to

do with any

value in the source, even if on an attribute called "id". It

needs only to

be unique to the node provided as argument to the function,

or to the

context node (in your case, "/profile") if none is given.

Given the code you have provided, in which you create only one
and assign it an ID unique to the  you have matched, there is a 
good chance that the observed duplication is actually

faithful to the

input, in which IDs are not unique (check to verify whether

this is not the

case). To guarantee uniqueness, reassign an ID to every

credential. Since

you are also creating new credentials, a second pass (your current 
workaround) is an appropriate place to do this. If you have

a requirement

to preserve IDs where they exist, this is a more complex problem and 
generate-id() is probably not part of the solution at all.

Cheers,
Wendell



=============================================================

=========

Wendell Piez

wapiez(_at_)mulberrytech(_dot_)com','','','')">wapiez(_at_)mulberrytech(_dot_)com

Mulberry Technologies, Inc.

http://www.mulberrytech.com

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           Direct Phone: 301/315-9635

Suite 207                                          Phone:

301/315-9631

Rockville, MD  20850                                 Fax:

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