Abstract: A method for automatically developing a proposal of advertising segments from a plurality of available advertising segments offered by an owner of a media presentation containing the advertising segments. A plurality of representations of available advertising segments are stored, and actual and/or speculative presentation characteristics are associated to each of the plurality of representations. A proposal is developed comprising a subset of the representations based on media buyer specified variables. The proposal is validated by ensuring that the speculative characteristics are satisfied upon creation of the media presentation containing segments purchased by the media buyer.