Got it. Still, there's no official mapping available, for the reasons shared before.
I'm a fan of digging into details, so alternatives that use the official platform API would be:
-if you're doing reads from the ValueStream, then you can use the various Query.....PropertyHistory services available at a Thing level to get your data through REST.
-If you're doing writes to the ValueStream I would deffinitely use only the ThingWorx way (logged properties), because of the buffering mechanism that we use for this situation.
If you deffinitely need to go to the DB, for any specific reason, what I would do is the following:
-Create a Thing with Property, set it to logged and set different values while changing its type
-in this way you should obtain a small amount of entries (=basetypes) in the VS that you can read and consult the data type.
Note: Be aware that ThingWorx 9.0 has a completely new Active-Active clustering mode, that can scale quite nice now.