1. That is just convention, services are free to filter on features that are present on a small subset of the data. 2. I don't know how Kayak specifically work

1. That is just convention, services are free to filter on features that are present on a small subset of the data. 2. I don't know how Kayak specifically works, they're just a general example of a customer-facing website that also vends an API that could be integrated with Voice UX. 3 / 4. Everyone has a different approach here and I'm not sure how Viv's would work... but Alexa's ownership model is app-based. 3rd parties build services that process the user's command however they want. They build the backend service, the Alexa voice integration endpoint, and (optionally) a companion website. Amazon owns the marketplace and physical interface. In this model, Uber owns the Uber integration, Lyft owns the Lyft integration, and whoever manages to search both Uber and Lyft would own that meta-service integration.