This ticket asks for a design proposal for a new IVOA DALI-style service to perform catalog queries that has essentially the same relationship to TAP that SIAv2 has to ObsTAP. It would be a modern successor to Simple Cone Search (SCS), but more importantly is meant to be a DataLink-friendly service for performing follow-on catalog searches based on catalog search results.

The raison d'etre of this proposal is that it is very difficult to use a TAP service as a service-descriptor-based DataLink follow-on, because unless a column in a search result includes a full ADQL query text as its value, there's no way to construct a TAP query from a simple column value.

It is always possible for a data publisher to define a publisher-specific DALI-style service, documented in a DataLink service descriptor, to satisfy its needs for follow-on queries (e.g., a DALI service for returning a light curve from an object ID obtained in another table). But it seems likely that interoperability would be enhanced by making available a standard framework for the definition of such a service.

This may be interesting to discuss within the NAVO DataLink group before presenting to an IVOA meeting.