XForms: Complex calculation for binding

Question

I am looking for a possibility to perform complex calculations for a binding. The following instance is given:

<root>
  <appointments>
    <appointment><date>2012-01-01</date></appointment>
    <appointment><date>2012-01-03</date></appointment>
  </appointments>
  <weeks />
</root>

The weeks node depends on the appointment nodes:

$weeks = 0
$week_begin = xs:date("1970-01-01")
for $appointment in //appointments/appoinment
  if # Check if $appointment is in new week
    $weeks = $weeks + 1
    $week_begin = # Do some more calculationx

My problem is that I don't know where to "put" those calculations. As you can see we need a loop with variables that can store some information between loop cycles. Therefore, I have evaluated the following options:

xforms:variable in combination with xforms:repeat => xforms:variable inside a repeat can't write to the "outside" scope
xforms:setvalue in combination with an extra instance that holds temporary variables and xforms:repeat
xforms:bind with calculate attribute => for loops in xpath are possible, but no variables

Any advice how to approach this problem? Thank you!

Can you give me one example of such complex calculations. Above given example is kind of incomplete. — Jayy, Feb 17 '12 at 14:50
I have some Ruby code that might make the "algorithm" more conrete... https://gist.github.com/c3bf9d7948a538b5bbd0 — lacco, Feb 17 '12 at 16:33

tohuwawohu · Accepted Answer · 2012-02-22T16:26:09.190

You could try to implement the calculation in Javascript that's triggered if the appointments nodeset has changed. If you're using Orbeon Forms, you could use the xxforms:script extension. The Orbeon wiki has an example how to set an instance value based on a javascript calculation.

Another solution would be to completely "externalise" the calculation and to create a little web service (XQuery?) that would return the result of the calculation. You could use the xforms:submit mechanism to feed that service and access its result.

XForms: Complex calculation for binding

1 Answers1