 Relevance implicatures like  (1)  are thought to arise from the maxim of Relation. Barb would have infringed this maxim unless her contribution were relevant to the purpose of the conversation. If Barb was being cooperative, then she was trying to answer Alan’s question. Given that working is incompatible with partying, it is inferred that Barb must have intended to communicate that she is not going to the party. Grice (1975: 34) thought other implicatures arise by flouting maxims. This happens when what a cooperative speaker says so patently violates a maxim that the hearer must infer that the speaker means something different. Irony is thought to arise from flouting the maxim of Quality  (§9).