1. A method comprising: identifying, by one or more processing devices, a target document based on information provided by a content provider through a user interface displayed on a computing device, the content provider being a purveyor of content that is distributable electronically; generating, by the one or more processing devices and based on information associated with the target document and information associated with a separate document that references the target document or that the target document references, a set of distribution terms representing concepts represented in the target document, the distribution terms defining one or more serving constraints comprising one or more conditions limiting distribution of the content, wherein generating the set of distribution terms comprises: analyzing the information associated with the target document to identify terms representing a first set of concepts related to the target document; revising the information associated with the target document by supplementing or replacing at least some of the information associated with the target document with at least some of the information from the separate document without revising content within the target document, the at least some of the information from the separate document including additional terms representing a second set of concepts different from the first set of concepts; analyzing the revised information associated with the target document to identify the additional terms in the revised information; and selecting, for inclusion in the set of distribution terms and from the terms and the additional terms, at least one of the terms and at least one of the additional terms; storing, in computer memory and by the one or more processing devices, the generated set of distribution terms; and distributing the content for inclusion in an additional document that is not the target document in response to the additional document satisfying at least one of the one or more serving constraints.
1. A method comprising: identifying, by one or more processing devices, a target document based on information provided by a content provider through a user interface displayed on a computing device, the content provider being a purveyor of content that is distributable electronically; generating, by the one or more processing devices and based on information associated with the target document and information associated with a separate document that references the target document or that the target document references, a set of distribution terms representing concepts represented in the target document, the distribution terms defining one or more serving constraints comprising one or more conditions limiting distribution of the content, wherein generating the set of distribution terms comprises: analyzing the information associated with the target document to identify terms representing a first set of concepts related to the target document; revising the information associated with the target document by supplementing or replacing at least some of the information associated with the target document with at least some of the information from the separate document without revising content within the target document, the at least some of the information from the separate document including additional terms representing a second set of concepts different from the first set of concepts; analyzing the revised information associated with the target document to identify the additional terms in the revised information; and selecting, for inclusion in the set of distribution terms and from the terms and the additional terms, at least one of the terms and at least one of the additional terms; storing, in computer memory and by the one or more processing devices, the generated set of distribution terms; and distributing the content for inclusion in an additional document that is not the target document in response to the additional document satisfying at least one of the one or more serving constraints. 10. The method of claim 1 , wherein the content comprises online advertising, and the additional document comprises one or more Web pages that have at least some subject matter in common with the target document.