Metamorph Cookbook

Use recursion to avoid the value of a field to be reset
4 lines of text should be extracted from a pica+ record which all begin with the $f-subfield of the 003@ and are followed by a combination of subfields in each 028@.
003@ ƒ01025201213
028@ ƒdFarīdƒcal-ƒaʿAbdalāwī
028@ ƒdFarīdƒaAl-ʿAbdalāwī
028@ ƒdFarid HamidƒaEl Abdellaouiƒ4nawi
028@ ƒdFarid HamidƒaAbdellaouiƒlEl

The rule of metamorph is defined as:
'<combine name="${personalname}${surname}${forename}${prefix}${addition}" value="##${pid}##,##${personalname}${surname}${forename}${prefix}${addition}##,##V##" flushWith="028@" reset="true"> <data source="003@.0" name="pid"/> <data source="028@.P" name="personalname" /> <data source="028@.a" name="surname"/> <data source="028@.d" name="forename"/> <data source="028@.c" name="prefix"/> <concat name="addition" delimiter=", " flushWith="028A" reset="true" prefix=" "> <data source="028@.n"/> <data source="028@.l"/> <data source="028@.g"/> </concat> </combine>'

The following output is expected:
'##1025201213##,##Abdellaoui, Farid Hamid##,##V##'
'##1025201213##,##Al-ʿAbdalāwī, Farīd##,##V##'
'##1025201213##,##El Abdellaoui, Farid Hamid##,##V##'
'##1025201213##,##ʿAbdalāwī, Farīd al-##,##V##'

In fact output looks like this:
'##1025201213##,##Abdellaoui, Farid Hamid##,##V##'
'####,##Al-ʿAbdalāwī, Farīd##,##V##'
'####,##El Abdellaoui, Farid Hamid##,##V##'
'####,##ʿAbdalāwī, Farīd al-##,##V##'
The reset=”true” option cleans the 003@ and 028@ before a new 028@ is read. A new 003@ doesn’t exist and it is therefore empty. Neither reset=”false” can be used here, because it will remember the value of the old 028@, like the “al-“ at end of the following lines which in fact only appears in the first 028@ field. '##1025201213##,##Abdellaoui, Farid Hamid al-##,##V##'
'##1025201213##,##Al-ʿAbdalāwī, Farīd al-##,##V##'
'##1025201213##,##El Abdellaoui, Farid Hamid al-##,##V##'
'##1025201213##,##ʿAbdalāwī, Farīd al-##,##V##'

The solution is use of recursion (prefix @):

The first element use the name “@pid” to declare a redirecting the value return to the input stream and it is done for each new 028@. The second element uses the redirected, but not reset value of 003@ to combine the new 028@ value which are reset.