The primary purpose of statements (utterances having a tag in the statement aspect) is to make claims about the world as in utterances such as ``It's raining outside'' or ``I need to get cargo there'' (the world includes the speaker) and in answers to questions. As a rule, the content of statements can be evaluated as being true or false. Note that the speaker does not have to be strongly claiming that something is true or false. This classification also includes weak forms of statement such as hypothesizing or suggesting that something might be true. Note also that we are only coding utterances that make explicit claims about the world, and not utterances that implicitly claim that something is true. As a intuitive test as to whether an utterance makes an explicit claim, consider whether the utterance could be followed by ``That's not true''. For example, the utterance ``Let's take the train from Dansville'' presupposes that there is a train at Dansville, but this utterance is not considered a statement. You couldn't coherently reply to this suggestion with ``That's not true''.
Figure 1 shows a decision tree for the statement aspect. The top level is an applicability condition that tests whether an utterance should be coded along this aspect. We only code utterances that make an explicit claim about the world. If the statement aspect is applicable, the decision tree then indicates how to select the appropriate tag. The key distinction for the Assert tag is that the speaker is trying to change the beliefs of the hearer. If this is not true, then a further distinction is made depending on whether the claim has been made previously in the dialogue or not.
Figure 1: Decision Tree for Statement Aspect