1. A method implemented by one or more computing devices for generating a narrative summary including at least one assertion describing an activity, the method comprising: receiving, by at least one of the one or more computing devices, a data record, the data record having associated activity information; retrieving, by at least one of the one or more computing devices, an assertion model, wherein the assertion model comprises at least one assertion template having a data field, wherein the data field is associated with one of a plurality of scenarios and wherein the plurality of scenarios include an activity scenario; filling, by at least one of the one or more computing devices, the data field of the at least one assertion template with the associated activity information based at least in part on a determination that the scenario associated with the data field is an activity scenario to thereby generate an assertion describing the associated activity information; and publishing, by at least one of the one or more computing devices, a narrative based on the assertion.