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> There are no "natural keys". They don't exist in nature. They don't exist as a thing in our physical reality. And when it comes to human-assigned identifiers,

> There are no "natural keys". They don't exist in nature. They don't exist as a thing in our physical reality. And when it comes to human-assigned identifiers, it should be emphasized much more strongly that whatever external thing you think is a good unique ID, it isn't. It seems to me that nature has plenty of natural keys, it’s human created constructs that don’t. For example, the periodic table has natural keys.

rini17 3y ago
Most of the time you don't interact directly with elements, but with molecules. Oh, and ions. And radicals. And and....
- TeMPOraL 3y ago
  And isotopes. And transient, unstable configurations that may exist for a brief moment before decaying into something that slots into the periodic table better. And also elements aren't a thing, quantum fields are. This is why you sometimes see things that just don't fit the idea of distinct atoms. But then quantum fields also aren't a thing. We don't know what exactly is the thing. We only have increasingly sophisticated working models.
  - rini17 3y ago
    No need to go to such philosophical depths. We're only poor engineers trying to come up with workable model. The periodical table of elements was a true boon and it is unlikely these "foreign keys" will change, but still - it alone isn't fully suitable as data model for chemistry.
dale_glass 3y ago
Yeah, but you don't want to use that as a primary key for your stock database. It'll work fine until you find you want to keep track of U-235 and U-238 separately. What constitutes identity is context-dependent. Yeah, on one level they're the same thing. On another they aren't.
- rzzzt 3y ago
  Make it a composite key of atomic and mass numbers, then.
  - xmcqdpt2 3y ago
    But then you need to have a stored procedure to maintain integrity every time an atom undergoes radioactive decay, that's got to be bad for performance!
  - c00lio 3y ago
    But then you'd miss on crystal structure to distinguish your diamonds from your coal.
    - OJFord 3y ago
      Which single element are they then? Surely such a system would have a products table with something like nominal element fk, purity, mass columns anyway. (And stock table with fk to products.) Then nothing wrong with 'natural' key on the elements, but sure, products are the thing you've (personally) made up, so of course there's no 'someone else's' key to use.
      - TRiG_Ireland 3y ago
        Diamonds and coal are both pure carbon (mostly carbon-12). So is graphite, and buckminsterfullerene, and a number of other things. Crystal structure matters a lot.
        OJFord 3y ago
        They're not pure carbon was my point. I wasn't saying crystal structure not important, I missed that but it'd be in my 'product derived from element x' table.
  - alexvoda 3y ago
    Actually, in that case that would not be a properly normalized key because the mass number (counts both protons and neutrons) depends on the atomic number(protons). Also it gets fun if you want to store anti-particles too.
MyThoughts100 3y ago
The periodic table is a human construct. So is the concept of an identifier.
- xmcqdpt2 3y ago
  Most elements are stable, especially most of the ones we deal with, and they fall in clear periods and rows based on chemical valence. This is true for main group elements and mostly true for transition metals. I think the periodic table was discovered, not invented. My guess is that whenever we communicate with some advanced alien species, the periodic table is going to be one of those things we share.
  - TeMPOraL 3y ago
    Periodic table is recording multiple different patterns in atoms. Some better than others. By nature, its a dimensional reduction. There are many alternative renderings of the periodic table (or spiral, or cube, or ...) emphasizing different regularities. The one you refer to is just the most popular rendering.
- rocqua 3y ago
  The concept of an identifier comes with the concept of a bijection (or at least a injection). That is a truly basic concept in Mathematics. You could argue Mathematics is a human construction. But at that point, isn't every concept a human construction? In that case it is hardly helpful, or meaningful to say a concept is a human construct, since all concepts are.
  - imtringued 3y ago
    The problem isn't the concept of a bijective function, it is picking the right function and that is a social problem.
- jameshart 3y ago
  I’d wager that nonhuman intelligences out there in the universe have analogous tables to the periodic table. And I suspect it would be possible for us to JOIN our periodic table onto theirs by matching on the atomic number field to create a mapping between, say, our names for the elements and theirs. That seems unlikely to be something we would be able to do with literally any other dataset that an alien civilization has. Their star catalog will contain many of the same objects ours does - but there won’t be an obvious key that lets us join them up. I guess there’s a few mathematical objects that would work - the list of Platonic solids maybe, or the symmetry groups… but in terms of real world physical things? Atomic numbers might be the only truly natural key there is.

rini17 3y ago

Most of the time you don't interact directly with elements, but with molecules. Oh, and ions. And radicals. And and....

TeMPOraL 3y ago
And isotopes. And transient, unstable configurations that may exist for a brief moment before decaying into something that slots into the periodic table better. And also elements aren't a thing, quantum fields are. This is why you sometimes see things that just don't fit the idea of distinct atoms. But then quantum fields also aren't a thing. We don't know what exactly is the thing. We only have increasingly sophisticated working models.
- rini17 3y ago
  No need to go to such philosophical depths. We're only poor engineers trying to come up with workable model. The periodical table of elements was a true boon and it is unlikely these "foreign keys" will change, but still - it alone isn't fully suitable as data model for chemistry.

dale_glass 3y ago

Yeah, but you don't want to use that as a primary key for your stock database. It'll work fine until you find you want to keep track of U-235 and U-238 separately. What constitutes identity is context-dependent. Yeah, on one level they're the same thing. On another they aren't.

rzzzt 3y ago
Make it a composite key of atomic and mass numbers, then.
- xmcqdpt2 3y ago
  But then you need to have a stored procedure to maintain integrity every time an atom undergoes radioactive decay, that's got to be bad for performance!
- c00lio 3y ago
  But then you'd miss on crystal structure to distinguish your diamonds from your coal.
  - OJFord 3y ago
    Which single element are they then? Surely such a system would have a products table with something like nominal element fk, purity, mass columns anyway. (And stock table with fk to products.) Then nothing wrong with 'natural' key on the elements, but sure, products are the thing you've (personally) made up, so of course there's no 'someone else's' key to use.
    - TRiG_Ireland 3y ago
      Diamonds and coal are both pure carbon (mostly carbon-12). So is graphite, and buckminsterfullerene, and a number of other things. Crystal structure matters a lot.
      - OJFord 3y ago
        They're not pure carbon was my point. I wasn't saying crystal structure not important, I missed that but it'd be in my 'product derived from element x' table.
- alexvoda 3y ago
  Actually, in that case that would not be a properly normalized key because the mass number (counts both protons and neutrons) depends on the atomic number(protons). Also it gets fun if you want to store anti-particles too.

MyThoughts100 3y ago

The periodic table is a human construct. So is the concept of an identifier.

xmcqdpt2 3y ago
Most elements are stable, especially most of the ones we deal with, and they fall in clear periods and rows based on chemical valence. This is true for main group elements and mostly true for transition metals. I think the periodic table was discovered, not invented. My guess is that whenever we communicate with some advanced alien species, the periodic table is going to be one of those things we share.
- TeMPOraL 3y ago
  Periodic table is recording multiple different patterns in atoms. Some better than others. By nature, its a dimensional reduction. There are many alternative renderings of the periodic table (or spiral, or cube, or ...) emphasizing different regularities. The one you refer to is just the most popular rendering.
rocqua 3y ago
The concept of an identifier comes with the concept of a bijection (or at least a injection). That is a truly basic concept in Mathematics. You could argue Mathematics is a human construction. But at that point, isn't every concept a human construction? In that case it is hardly helpful, or meaningful to say a concept is a human construct, since all concepts are.
- imtringued 3y ago
  The problem isn't the concept of a bijective function, it is picking the right function and that is a social problem.
jameshart 3y ago
I’d wager that nonhuman intelligences out there in the universe have analogous tables to the periodic table. And I suspect it would be possible for us to JOIN our periodic table onto theirs by matching on the atomic number field to create a mapping between, say, our names for the elements and theirs. That seems unlikely to be something we would be able to do with literally any other dataset that an alien civilization has. Their star catalog will contain many of the same objects ours does - but there won’t be an obvious key that lets us join them up. I guess there’s a few mathematical objects that would work - the list of Platonic solids maybe, or the symmetry groups… but in terms of real world physical things? Atomic numbers might be the only truly natural key there is.