If  you try to print that:

   PPMSEArrayParser parse: (FMMSEPrinter new onString
beginDocument;
beginElement: 'Element';
beginAttribute: 'attribute';
primitive: 'it''s here';
endAttribute: 'attribute';
endElement: 'Element';
endDocument;
stream) contents 

you will see that instead of having the string 'it''s here' as value of the attrinute, I will retrieve a collection with two strings #('it' 's here'). 
I was expecting to retrieve my string  in one full part. So I wonder if this should be the normal behaviour or if we have to re-compose the string by ourselves ?