Subject: Re: [linux-audio-dev] LADSPA proposal ...
From: Alfons Adriaensen (fons.adriaensen_AT_alcatel.be)
Date: Wed May 19 2004 - 16:38:09 EEST
On Wed, May 19, 2004 at 12:18:25PM +0100, Steve Harris wrote:
> >What's missing ?
>
> Semantics. You can define a single layer metadata system with virtually no
> (machine) semnatics, eg.
>
> hasTitle: "my plugin"
> hasPortCount: "3"
> ...
> but you quickly run into problems when trying to encode anything
> interesting, like port 3 is a "contol in port" with a lower range of 0 and an
> upper range of the "max delay" port, it uses milliseconds as its units,
> should be controlled logarithmically...
>
> You can hack it all in lexically, but then your back to a sitatution where
> you can paint yourself into a corner w.r.t. back/forward compatibility.
As far as I can see, everything that can be expressed by an RDF graph or
a set of triplets or the eqeuivalent XML can be equally well expressed by
nested property lists in LISP or even nested structs in C/C++.
The use of URIs in this case seems to me like complete overkill, there is
no requirement that every identifier is webwide uinique since we have a
well defined context.
> To get round this, good metadata languages are defined so that they are
> monotonic and with a few other interesting properties that logicians care
> about.
At some point in your program, metadata will be translated into variable
values. If at that point you decide that B overrides A, things are no
longer monotonic, and there's nothing to stop you from doing that even
if the values of A and B were originally derived from RDF.
When you add a field to a C struct, that does not change the value of any
other, so I'd say that is monotonic as well, unless you decide to destroy
that property as described above.
> If you are interested in the mathematical properties, then read the RDF
> model theory: http://www.w3.org/TR/rdf-mt/ its a bit dry though :)
> NB I wouldnt suggest we require RDFS for LADSPA, just RDF. RDFS makes it
> much more challenging to implement if you dont want to use a standard
> library, and we really wouldn't gain much.
Do you mean you would have a dedicated parser that must be updated each
time a property is added, rather than a general one driven by a schema ?
In that case nothing is gained at all.
-- FA
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