If you need some defined XML entities like é within the IzPack installation XML, you can’t use it there. The reason: they aren’t defined. But you can define a subset within your XML:
<?xml version="1.0" encoding="iso-8859-1" ?>
<!DOCTYPE installation [
<!ENTITY % iso-lat1 PUBLIC "ISO 8879:1986//ENTITIES Added Latin 1//EN//XML"
"http://www.oasis-open.org/docbook/xmlcharent/0.3/iso-lat1.ent">
%iso-lat1;
]>
<installation version="1.0">
<!-- start here -->
</installation>
These additional lines include the usual entities. It is now possible to use:
<authors>
<author name="André Rothe" email="andre.rothe@domain.local" />
</authors>