Problematic Set-Denoting Temporal Expressions in the Framework of ISO-TimeML

This study investigates how to represent set-denoting temporal expressions with ISO-Time ML, a state-of-the-art framework for representing time expressions. Specifically, we will show its limitations, caused by characteristics of TIMEX3, i) the freq attribute can not represent both the frequency of time points and the time granularity at the same time. ii) set expressions structurally containing another set expressions can not be annotated in the current framework. iii) value attribute can not contain values of complex set-denoting expressions. iv) there are set-expressions that have no set marker. These limitations reveal that TIMEX3 needs to be modified or extended to represent those problematic temporal expressions.