Social connected messages must be associated with either content items or marketing goals, but it is possible to trigger a marketing goal using the API:
GoalUtil.RegisterEventParameters("Goal Name", new Dictionary<string,string>());
This fires the goal, and has the additional feature of allowing you to replace tokens in the message text. For example, if you defined a Goal named "Mayor", and create an associated Facebook message with this text: "I've just become mayor of $place."
, you can cause this to appear on a user's Facebook wall specific text by doing this:
var tokens = new Dictionary<string, string>();
tokens.Add("place", "New York");
GoalUtil.RegisterEventParameters("Mayor", tokens);
This message will appear on the users wall: "I've just become mayor of New York." Notice that the dollar sign appears in the message, but not in the token key value added to the dictionary. GoalUtil is in the namespace: Sitecore.Social.Core.Publishing.Utils, in the Sitecore.Social.Core.dll.
In addition, when a message is associated with a goal, the following rule is added to the goal:
where true (actions always execute)
post associated messages
You can replace the always true condition with different logic, possibly using Rules Engine conditions you have authored, to restrict messages to meet the required business logic.