[ivoa-std/VOEvent] Registry matters (#11)

[Dave Morris]

I agree, this is indeed a good reason for registering services in the 
registry.

-- Dave

On 2020-11-03 09:00, Baptiste Cecconi wrote:
> Another good thing with having the VOEvent stream registered in the
> Registry is the capability to advertise for a service that serves past
> events emitted from that steam. For instance:
> 
> ```
>          <relationship>
>              <!-- TAP service containing/archiving all previous
>                events produced by this stream -->
>              <relationshipType>IsSourceOf</relationshipType>
>              <relatedResource 
> ivo-id="ivo://vopdc.obspm/imcce/meteorshower/epn"
>                >Meteor Shower prediction EPN-TAP 
> service</relatedResource>
>          </relationship>
> ```