1 Introduction
Table 2: Alignment of RST-DT relations for those labels that were identified as theoretically interesting cases of discrepancies between the three mapping proposals.
['RST-DT label PDTB label', 'Temp. Synch.', 'Temp. Asynch.', 'Cont. Cause', 'Cont. Condition', 'Comp. Contrast', 'Comp. Pragm. contr.', 'Comp. Concession', 'Expansion Conjunction', 'Expansion Chosen alt.', 'Expansion Exception', 'Expansion Instantiation', 'Expansion Specification', 'Expansion List', 'Expansion EntRel', 'Total']
Regarding the first label, PDTB does not have a directly corresponding label for RST-DT’s Comparison label. Because the RST-DT annotation manual explicitly defines these relations as non-contrastive, \namecitesanders2016 mapped this label to Conjunction while \namecitebunt2016 mapped it to Contrast. This distribution is similar for explicit and implicit instances of Comparison. Typical markers for explicit instances are while, but and however. We therefore conclude that RST-DT ’s Comparison should be mapped to both PDTB Conjunction and Contrast. Finally, we consider the labels Background and Circumstance. UniDim mapped Background to PDTB Conjunction and Asynchronous, whereas ISO only mapped it to Conjunction. Regarding Circumstance, UniDim mapped it to PDTB Conjunction, Synchronous and Asynchronous, and ISO only mapped it to Synchronous. RST-DT’s Background and Circumstance therefore seem to be more general labels than both UniDim and ISO predicted. This could be due to the lack of corresponding label in PDTB.