[MOBY-l] Re: [MOBY-dev] lease versus agent for registry updating
gordonp at ucalgary.ca
Mon Aug 15 10:32:26 EDT 2005
A few advantages of the lease are not really advantages in practice:
1. No one will manually update their lease, they will put it in a cron
job. Therefore you either need to edit your crontab, or remove from the
RDF file in the agent case. Both are just as likely to be ignored by an
administrator when a service stops working.
2. Specifiying that the service is valid for a certain amount of time is
mostly useful for testing purposes. You should really be using a test
registry in that case, not posting dubious services to the production
The chief advantages of the agent are:
1. You can trace the registration and deregistration of a service to a
particular domain name. It's not great security, but at the very least
people require some serious work to pose as the NCBI on purpose (by
hacking their Web domain), and cannot by mistake (e.g. "I registered my
service using the NCBI authority ID because I'm using gi's").
2. The RDF for the services does not have a single point of failure
(i.e. the central registry).
The one agent feature I would l;ike though is that I can call MOBY
Central to tell it that I've changed my RDF, i.e. pushing a
refresh. It's not critical though. If the agent runs once a day, you may
get some latency on bad services, but it's not the end of the world.
Tim Berners-Lee got a lot of flack for his Web idea because it didn't
enforce that what people linked to existed. "People won't use it, they
may end up at dead links!" they said...
>>>>>>"Boris" == Boris Steipe <boris.steipe at utoronto.ca> writes:
> Boris> Why not put the burden of the lease on the agent to combine
> Boris> the advantages of both models? I.e. if service is down for
> Boris> less then a specific time, it might not get deregistered but
> Boris> only flagged as temporarily unavailable ... then un-flagged
> Boris> as it comes up again, except if it's down for, say > 1week,
> Boris> then it gets deregistered.
> Boris> $0.02
>Actually, this is just a modification of the agent idea, and not a
>lease at all.
>The idea of a lease is not just a burden on the service provide, but
>it also has a positive advantage. It give the service provide the
>ability to control how long they want the service advertised for in
>the registry. Of course, they can do the same thing with the agent,
>more or less; they just remove the RDF document after a certain time,
>although, they don't know exactly when the agent will remove them.
>At the end of the day, I am not sure that the two mechanisms are
>hugely different in terms of their functionality. It seems to me that
>the lease puts slightly more weight on the service provider, but will
>provide better garbage collection (just become someone leaves an RDF
>document on the web, does not mean that their service is actually
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