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

[Joachim Wackerow]

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>