Embodiments are directed towards automatically generating extraction rules for extracting fields from event records. An extraction rule application receives field data describing the fields to be extracted (including one or more examples) and a collection of event records that may be a representative sample set from a larger set of events records. The extraction rule application generates extraction rules based on the event records and the field data. These extraction rules may be ranked using a determined quality score. Quality scores for extraction rules may be determined based on various metrics related to the operation of the extraction rules and the resultant extracted values. Preferred extraction rules may be determined by ranking the extraction rules based on their quality scores. Also, natural language expressions may be used to create, edit, or modify extraction rules.