[rsp] Query functionality form use cases

Hello All,

We had an interesting discussion last friday. From the
 use cases and queries we saw, I identified some features that seem to 
be needed/useful:

- subqueries
- time windows
- query from multiple streams
- join with static data
- aggreagates
- timestamps on graphs
- sequence? (we didn't discuss it but look at the OpenGov use case)

If
 your use case has other stuff don't hesitate to add some sample queries
 in the wiki, or through this list, so that we can discuss that.

Other
 than that we have seen that using system time for annotating data items
 can be misleading. If we specify a window, we probably want to refer to
 an application time. However this brings problems as well (e.g. order 
guarantees).

Finally, Daniele and I started working on the 
semantics of time windows on timestamped graphs. If you want to take a 
look, edit or rewrite it:
https://www.w3.org/community/rsp/wiki/RSP_Query_Semantics

We
 are also considering the case when the annotation is an interval, but 
it's not too clear what the window should do in that case. Any thoughts 
welcome.

By the way the minutes are online https://www.w3.org/community/rsp/wiki/Telecon_21.02.2014


best,
Jean-Paul