Benjamin Bock asked me recently about how I would model a mole of salt in a topic map.
That is a good question but I think we had better start with a single grain of salt and then work our way up from there.
At first blush, and only at first blush, do many subjects look quite easy to represent in a topic map.
A grain of salt looks simple to at first glance, just create a PSI (Published Subject Identifier), put that as the subjectIdentifier on a topic and be done with it.
Well…, except that I don’t want to talk about a particular grain of salt, I want to talk about salt more generally.
OK, one of those, I see.
Alright, same answer as before, except make the PSI for salt in general, not some particular grain of salt.
Well,…., except that when I go to the Wikipedia article on salt, Salt, I find that salt is a compound of chlorine and sodium.
A compound, oh, that means something made up of more than one subject. In a particular type of relationship.
Sounds like an association to me.
Of a particular type, an ionic association. (I looked it up, see: Ionic Compound)
And this association between chlorine and sodium has several properties reported by Wikipedia, here are just a few of them:
Molar mass: 58.443 g/mol
Appearance: Colorless/white crystalline solid
Odor: Odorless
Density: 2.165 g/cm3
Melting point: 801 °C, 1074 K, 1474 °F
Boiling point: 1413 °C, 1686 K, 2575 °F
… and several others.
If you are interested in scientific/technical work, please be aware of CAS, a work product of the American Chemical Society, with a very impressive range unique identifiers. (56 million organic and inorganic substances, 62 million sequences and they have a counter that increments while you are on the page.)
Note that unlike my suggestion, CAS takes the assign a unique identifier view for the substances, sequences and chemicals that they curate.
Oh, sorry, got interested in the CAS as a source for subject identification. In fact, that is a nice segway to consider how to represent the millions and millions of compounds.
We could create associations with the various components being role players but then we would have to reify those associations in order to hang additional properties off of them. Well, technically speaking in XTM we would create non-occurrence occurrences and type those to hold the additional properties.
Sorry, I was presuming the decision to represent compounds as associations. Shout out when I start to presume that sort of thing. 😉
The reason I would represent compounds as associations is that the components of the associations are then subjects I can talk about and even add addition properties to, or create mappings between.
I suspect that CAS has chemistry from the 1800’s fairly well covered but what about older texts? Substances before then may not be of interest to commercial chemists but certainly would be of interest to historians and other scholars.
Use of a topic map plus the CAS identifiers would enable scholars studying older materials to effectively share information about older texts, which have different designations for substances than CAS would record.
You could argue that I could use a topic for compounds, much as CAS does, and rely upon searching in order to discover relationships.
Tis true, tis true, but my modeling preference is for relationships seen as subjects, although I must confess I would prefer a next generation syntax that avoids the reification overhead of XTM.
Given the prevalent of complex relationships/associations as you see from the CAS index, I think a simplification of the representation of associations is warranted.
Sorry, I never did quite reach Benjamin’s question about a mole of salt but I will take up that gauge again tomorrow.
We will see that measurements (which figured into his questions about recipes as well) is an interesting area of topic map design.
*****
PS: Comments and/or suggestions on areas to post about are most welcome. Subject analysis for topic maps is not unlike cataloging in library science to a degree, except that what classification you assign is entirely the work product of your experience, reading and analysis. There are no fixed answers, only the ones that you find the most useful.