No, you can’t concatenate strings in XML but you can define XML resources.
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE resources [
<!ENTITY appname "MyAppName">
<!ENTITY author "MrGreen">
]>
<resources>
<string name="app_name">&appname;</string>
<string name="description">The &appname; app was created by &author;</string>
</resources>
The original answer was posted here.