1) I remember seeing answers in the forum indicating that the User ID give to a skill is unique to a user, and unique per developer account, but consistent across different skills by the same developer. 2) However, I have also seen it said that when a user disables a skill, then re-enables it, that their User ID changes. These both can't be true. Has the implementation of (2) superseded (1)?
User ID is absolutely unique per skill, unfortunately. This is becoming a bigger and bigger concern for the things we're building. Long term, I think a shared identifier of some sort is going to become more important to this ecosystem than any of the other pending feature requests.
Yes, it's an issue. I just introduced cross skill advertising. I'd love to be able to measure the pass through rate. I.e. how effective is my advertising? Without this I have no way of working out if someone who saw the ad, followed through and started using the other skill. Now, if Amazon introduced cookies to skills....
Yep, that's one of the use cases I was thinking of. Cross-skill promotion was one of the things that was important to us when we built out CompliBot and InsultiBot. There are a bunch of other cases, as well - I need to find some time to formulate the argument fully.
If you are still interested, let me know. I'm writing the stuff I'm doing so that it could eventually be an ad-sharing network between skill developers. I.e. a service where you can identify your skill, and ask for an ad. Later register that you served up that ad. Quotas could be set so that you could have a sort of impression barter system. I.e. if you've served up an ad for my skill X times, then you won't be sent my app to advertise until my app has served up at least X impressions of your skill. First I have to prove that cross skill advertising has any benefit at all. Since I can't do a direct comparison, I have to wait a week or so to see if the numbers on the skills trend with any significance.
From the OP, 2) should is the correct description of current behavior. In other words, a user ID is only unique within the context of that skill, and once they disable and re-enable the skill they are considered a totally new user. -Nick