תרגום - אנגלית-איטלקית - Fault Trees A fault tree is a hierarchic chart...

Not sure about the 'fault tree' translation, i couldn't find any actual italian equivalent; i think it might exist an exact expression for it - but don't know it since it's so specific language.
not sure also about the top-level and high-level meaning, if they're meant as synonyms or they refers to two different kind of object. maybe reading the whole text would help :)