[racket] Liitin screencast tutorial

Those timestamps in Liitin are best described as transaction times to the
system. It may sometimes be "enough" to tell about the objects history, as
in the tutorial's "savings". Another "in-built" feature may be more useful
for critical instances, say storing wheather measurings. If the meter is
faulty or the communication to the server is slow or delayed, it should not
influence the data entry. Instead, you could create a Liitin object
identified as the true measuring time. If the value proves to be faulty, you
simply save an update ("Save update" button in the tutorial), and the
functions calling the value will then receive the corrected value
automatically.

This is the system's methods to deal with this kind of issues, but it is not
meant to replace the purpose of the metadata. Instead, if the metadata
contained errors, you could correct it afterwards. All of these actions will
also leave traces, so you can check what transactions took place and when.

br, jukka

> -----Original Message-----
> From: users-bounces at racket-lang.org
> [mailto:users-bounces at racket-lang.org]On Behalf Of Hendrik Boom
> Sent: 06 March 2011 01:54
> To: users at racket-lang.org
> Subject: Re: [racket] Liitin screencast tutorial
>
>
> On Sat, Mar 05, 2011 at 10:11:59PM +0200, Jukka Tuominen wrote:
> >
> > Even with these challenges solved, you would still need to dig
> deeper in the
> > overall architecture to solve issues that Liitin tries to
> address.  In the
> > overall concept; accumulate life-long personal data and methods
> and interact
> > with others and eventually the whole human kind heritage (data AND
> > methods)... (can you hear the angel chorus :)
>
> One of the difficult aspect of life-long data accumulation is dealing
> with data alrady accumulated before the new  system came into existence.
>
> I seem to remember a historian studying some phenomonon starting only
> from the data that computer-stored information became available.  There
> was an uproar of the form "Does this mean that history is starting all
> over again and all the precomputer stuff is forever forgotten?"
>
> -- hendrik
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