1. A system, comprising: a user input device; and a processor programmed to: detect, via the user input device in association with a social network user interface, user input comprising a social network notification symbol followed by a social network tag, where the social network tag comprises a text keyword that identifies a social network topic within the social network; determine a subset of social network users within the social network that follow the social network topic identified by the text keyword of the social network tag; define a referential third-party social network user notification subset within the social network as the determined subset of social network users within the social network that follow the social network topic; and publish, to the defined referential third-party social network user notification subset within the social network, a referential third-party social network notification comprising the detected user input that comprises the social network notification symbol followed by the social network tag.
1. A system, comprising: a user input device; and a processor programmed to: detect, via the user input device in association with a social network user interface, user input comprising a social network notification symbol followed by a social network tag, where the social network tag comprises a text keyword that identifies a social network topic within the social network; determine a subset of social network users within the social network that follow the social network topic identified by the text keyword of the social network tag; define a referential third-party social network user notification subset within the social network as the determined subset of social network users within the social network that follow the social network topic; and publish, to the defined referential third-party social network user notification subset within the social network, a referential third-party social network notification comprising the detected user input that comprises the social network notification symbol followed by the social network tag. 4. The system of claim 1 , where the user input further comprises a logical combination operator specified by the user and an additional social network tag, where the additional social network tag comprises an additional text keyword that identifies an additional social network topic within the social network, and the processor is further programmed to: determine an additional subset of social network users within the social network that follow the additional social network topic identified by the additional text keyword of the additional social network tag; and where, in being programmed to define the referential third-party social network user notification subset within the social network further, the processor is programmed to: define the referential third-party social network user notification subset within the social network as a logical combination of the determined subset of the social network users that follow the social network topic and the determined additional subset of the social network users that follow the additional social network topic.