1. A method performed by data processing apparatus, the method comprising: providing data that cause presentation of a model development user interface; receiving first model rule data through the user interface, the first model rule data specifying a first model rule that specifies a first characteristic of a violating resource and a threshold score for the first characteristic, wherein the first model rule data specifies a phrase and a threshold number of instances of the phrase that, when included in resource, are indicative of the resource being a violating resource; receiving additional model rule data through the user interface, the additional model rule data specifying one or more additional model rules, each of the additional model rules specifying an additional characteristic of the violating resource and an additional threshold for the additional characteristic; receiving, for each of the additional model rules, relationship data through the user interface, the relationship data specifying sets of the additional model rules that violating resources satisfy; and providing data that cause a hierarchical presentation of the first model rule and the additional model rules, the first model rule being presented at a highest hierarchical position and each of the additional model rules being presented at a descendent hierarchical position based on the relationship data, the data further causing presentation of a relationship indicator for each of the additional model rules, the relationship indicator specifying the sets of additional model rules that must be satisfied to classify a resource as a violating resource.