The main reason for introducing this framework is to allow us to characterize algorithms that have previously been described in different traditions and to compare their formal properties within a single unified framework.
whereas this type of framework has previously been used to characterize algorithms in the stackbased family (Nivre 2003(Nivre , 2006bAttardi 2006), it is here being used also for the listbased algorithms first discussed by Covington (2001).