Node Visibiliy

GELLO code will be used to display an ELEMENT node or not. GELLO for node visibility can also be applied for CLUSTERs or data groups. This is important for:

• managing computer screen real estate

• developing 'smart forms' that show and hide nodes depending on value(s) entered elsewhere in the archetype tree

• excluding non-visible nodes from the resulting HL7 message

Apple archetype example

Lets go back to the apple archetype. The example here will add GELLO node visibility to 'Total Cost'. When values have been entered for the higher nodes 'Cost' and 'Number', and the IsCalculated tag GELLO has calculated a value , we may decide its fair enough to make the node visible. Another example where node visibility is useful has been in the pathology domain, where calculation of certain values need only be done and displayed where certain other fields have been entered, eg the calculation of electronic glomerular filtration rate (eGFR).

Open CEN13606-Apple.v1.xml again. Set the VisibleAtStart metadata tag for 'Total Cost' on the RHS to false.

Here's a walk through of the GELLO required:

1. Usual beginning:
   
   

   let o:observation = parameter[1]

2. See if 'Cost' and 'Number' have values. This time we'll just retrieve them as the general type/class Observation:
   
   

   let o1: Observation =
    if o.isdefined() then
         o.find_observation('1.2')
    else
         o
    endif
   let o2: Observation =
    if o.isdefined() then
         o.find_observation('1.3')
    else
         o
    endif

3. Set up the test:
    

   let VisA:boolean =
    if o1.isDefined() then
      if o1.value_asPQ().value > 0.0  then
        true
      else
        false
      endif
    else
       unknown
    endif

    let VisB:boolean =
    if o2.isDefined() then
      if o2.value_asReal() > 0.0  then
        true
      else
        false
      endif
    else
      unknown
    endif

4. Run the test and return the result (as a boolean):
   
   

    Let Result : Boolean =
        If VisA = true and VisB = true then true
            else false
        endif

   Result

5. Save your work