1. A method executed by a computer, the method comprising: defining a plurality of reference event categories each associated with at least one reference action from an ontology based on: an intention class representing a purpose of each reference action, an activity type class representing a nature of each reference action, a movement class representing an implementation of each reference action, a target class representing an object of each reference action, and a gain class representing result of each reference action, wherein the ontology is operable to define each action by meaning of an event such that, based on linguistic rules associated with each reference action, the action belongs to no more than one reference event category; and for each given message, disassembling the given message in a database defined by the intention class, the activity type class, the movement class, the target class and the gain class; comparing the disassembled message with at least one reference event category; and generating at least one standardised event representing a correspondence between the disassembled message and the reference event category, wherein: each of the linguistic rules corresponds to a type of reference action that is represented in different fields of messages when the messages are generated from different log-generating systems; each of the linguistic rules associates the type of reference action with a predicted result of the reference action; the meaning of the event is defined based at least in part on the type of reference action and the predicted result; and the standardised event is operable to represent the given message by meaning regardless of differences in arrangements of fields between the message and other messages having the same meaning.