Site argument representation. Site arguments add detail to core arguments, and each site argument is paired with one core argument. (A) In most tasks we link both core and site arguments to given protein nodes. This minimizes the number of outgoing edges per trigger node, simplifying unmerging, but loses the connection between site and core arguments. (B) In the EPI task, all events with site-arguments have a single core argument, so linking sites to the trigger node preserves the site/core connection. (C) To both limit number of arguments in trigger nodes and preserve site information, event arguments using sites could be linked to protein nodes through the site entity. However, in this approach the core argument would remain undetected if the site wasn't detected.
Björne et al. BMC Bioinformatics 2012 13(Suppl 11):S4 doi:10.1186/1471-2105-13-S11-S4