[DDI-users] Re:Adding tags to the DDI (Andrew L Arnott)

[Andrew Arnott]

Achim,

The goal is a kind of skip pattern, that's true.  Specifically what I'm
looking for is an answer to the problem: If I have a page of questions on
divorce details, but on a previous page the question "Were you ever
divorced?" were answered No, then the whole page (or even a small section of
the page) on divorce later in the questionnaire ought to be skipped.  By
skipped, I mean that the questions should never show up on the web page (or
grayed out, whatever you wish).  

So to me, the most convenient way of supporting this with the DDI is just
surround those divorce details questions in a varGrp and use the
conditionals within that varGrp.  It sounds like you are suggesting that
rather than make up the new DDI tags to use right here, we adopt MathML's
syntax, or leave DDI extensible so that additional schemas can be used
within DDI -- perhaps schemas best used for this and similar tasks.  While
that idea appeals to me, MathML's example that you included simples
extremely complex and hard to read, compared to the three or four lines of
code I had as an example.  Maybe though, if DDI left some extensibility for
third-party schemas in its next version, we could each use our favorite
schemas to perform that conditional work.

Of course then we lose the 100% compatibility that the DDI gives us right
now, which would be a sore loss.

- Andrew
-----Original Message-----
From: ddi-users-bounces at icpsr.umich.edu
[mailto:ddi-users-bounces at icpsr.umich.edu] On Behalf Of Joachim Wackerow
Sent: Wednesday, January 21, 2004 3:35 AM
To: Data Documentation Iniative Users Group
Subject: Re: [DDI-users] Re:Adding tags to the DDI (Andrew L Arnott)

Another comment.

The goal seems to me to describe conditional connections between several 
questions/variables. One use of conditional connections is the "skip 
pattern", an other use is the construction of new variables on the basis 
of existing variables. With a formal description of this conditional 
connections it would be possible for example to generate a SPSS command 
setup with "select if" statements out of a DDI description.

A very flexible way would be to extend the DDI elements varGrp and/or 
var with the possibilities of MathML. Then it would not be necessary to 
build new elements, with the chance of new restrictions. The main 
problem would be, how to extend DDI with other DTDs/Schemas. But the 
same question exists in other areas of the DDI, like bibliographic 
information (MARC).

Achim

Below is Andrew's example in MathML:

Possible rendering in Unicode: { VG8F1| V1=5 ? V2=3 ? V3=2 }

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE math PUBLIC "-//W3C//DTD MathML 2.0//EN"
            "http://www.w3.org/Math/DTD/mathml2/mathml2.dtd">
<math xmlns="http://www.w3.org/1998/Math/MathML">
   <semantics>
     <set>
       <bvar>
         <ci>VG8F1</ci>
       </bvar>
       <condition>
         <apply>
           <or/>
           <reln>
             <eq/>
             <ci>V1</ci>
             <ci>5</ci>
           </reln>
           <condition>
             <apply>
               <and/>
               <reln>
                 <leq/>
                 <ci>V2</ci>
                 <ci>3</ci>
               </reln>
               <reln>
                 <eq/>
                 <ci>V3</ci>
                 <ci>2</ci>
               </reln>
             </apply>
           </condition>
         </apply>
       </condition>
     </set>
   </semantics>
</math>



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