Chris: I think that both Yves and Samer answered to all your questions. However, I played a log with the ontology today to map musicbrainz with it. I also discussed a lot with Yves about many things and some issue has been discovered (small ones) and we discussed a lot about how to make the ontology clearer and simpler to understand.

We developed a couple of workflow, we will have to rework some definitions, re-introduce some basic properties to explicits relations. With a data dump of musicbrainz using MO and a document explaining the mapping, I think (and hope) and the revision 1.10 of the ontology will be much more easy to understand.

Take care,

Fred

Firstly, about the time varying properties like band membership etc. This is issue was forseen and
is part of the reason why we adopted an event based knowledge representation so deeply into the
system. In this case, one would declare a ‘Membership event’ which covers the time interval for which
the membership holds. A query such as memberOf(‘BritneySpears’,X) would then only have meaning
relative to a current time (ie it would be a modal query). The Event ontology is indeed an expression
of the perdurantist view – the least offensive definition for an event we have found is ‘an event is a
classification of a region of space-time (or just time if space is irrelevant).

From this point of view, a Sound (event) is the classification of some region of space-time as containing
or supporting an acoustic field – ie a *physical* thing. If the sound is recorded as it happens, there is
another event which characterises the transduction of the acoustic field into a signal. At this point, we
consider the signal to be an informational/mathematical objects and we no-longer need events to
describe it.

In the case of electronic music produced directly a digital signal, there is no recording and no sound
until the signal played through a speaker. This is also described using two events – the resulting sound,
and a ‘Playback’ event which mirrors a recording, and represents the realisation of an informational object (the signal) as a physical process (the sound).

There is no obstacle to representing such things in the ontology. It just means that if you ask for recording events, or objects resulting from recording events, you won’t get this electronic music.
You woudl have to ask for, say, signals which are ultimately derived from this or that Work – there
would have to a property relating a Work (conceptual) or a score (informational) directly to the resulting
signal. For example, if I use timidity to synthesise a midi sequence using certain parameters, there is
a functional relation tying the midi score to the resulting signal.

If the situation is more complicated, with say, a live laptop performance, with a human controlling the
synthesis in unpredictable ways while it is going on, and signal going directly to a file, then there is a
(physical) Performance event, but the product is not a Sound, but a Signal.

And yes, Sound should not be a subclass of MusicalExpression.

Cheers,

Yes – you are totally right, we consider the sound as being the “physical sound” itself. I think the cognition of the sound is thus not expressed here, but this could surely be an extension of the ontology! That’s one of the main point now: the ontology provides “anchor points”, so we can act as a backbone ontology for other stuff: automatic feature extraction (often linked to the concept of Event), cognition (linked to this Sound concept), recording stuff (microphones, DAC, linked to Recording)…

In the case of electronic music, that is an issue. We could maybe consider the sound as an informational object there? To be discussed…

Btw, are you a member of the mailing list? Its archives are here:
http://groups.google.com/group/music-ontology-specification-group

It could be great to chat a bit more about all these points on this list! Could you send your comments there?

Thanks,
y

The comment for sound is:

A subclass of MusicalExpression, representing a sound.

I’m not sure if this is intended to be a text definition. If so, it commits the use/mention mistake. May I suggest the wording of the definition denotes the instances the class represents. Instead of “A subclass of MusicalExpression”, which not say “A MusicalExpression” (assuming this definition is correct)?

According to this comment, A sound represents a sound. This is circular.

I think you want to mention the phsyics of sounds (and possibly their perception as well – you should take a position on the hoary old philosophical chestnut about sounds in a forest devoid of listeners).

Meriam Webster has:

mechanical radiant energy that is transmitted by longitudinal pressure waves in air or other material medium and is the objective cause of the sensation of hearing

Which seems reasonable.

However, this would cause problems for electronic music in which the “recording” is made from entirely synthesised sounds
Can I use the MO to express statements like:

Theremins sound spooky to me

Black metal sounds like cats being strangled

What about found sounds? And this:
http://www.amazon.com/Stockhausen-Helikopter-Streichquartett-Helicopter-Quartet/dp/B00004NJJX

It is interesting to see the MO address issues of time. It’s widely known that OWL has problems with time (which the OWL time ontology do not solve). To illustrate, let me take one example from the MO documentation:

2 Britney Spears
3
4 …
5

6
7 Kevin Federline
8 …
9

OWL assumes a static world in which BritneySpears married_to KevinFederline holds eternally. This is not an accurate representation of reality. relations between continuants (3-Dimensional entities such as Britney Spears or Britney Spears’ hair) hold for temporal durations.

BritneySpears stands in a married_to Jason Allen Alexander on 1/3/05, and in a married_to relation to Kevin Federline on 2/27/07. An OWL reasoner would conclude that Britney Spears is polyandrous.

The solution in this case is to explicitly represent dependent continuants such as Marriages. The two different marriage instances that Britney Spears participates_in could be time-indexed. A similar solution could be applied to other relationships such as being in a band together. This would involve some changes to the MO.

This solution is unsatisfactory for certain kinds of relations. For example, Britney Spears Hair was part_of Britney Spears on 1/3/05, but that same aggregate of hairs is not part_of Britney Spears on 2/27/07. Here, representing what are clearly relations as instances of relationship classes is unsatifactory, as are other solutions such as turning Britney Spears into a time-worm (the so-called perdurantist ontological position, in which there are no continuants such as Britney Spears, only processes, such as the process of Britney Spears life and parts of Britney Spears life).

This may not be such a problem for the MO, which does not in general deal with changing anatomical features of artists; the primary entities in MO are processes such as performances where this problem does not arise.