[Reply to BO list]
On Fri, Dec 14, 2012 at 5:25 PM, Craig James <cja...@emolecules.com> wrote:
> Thanks to Tim, there is a new version of the OpenSMILES specification, in
> both HTML and PDF formats:
>
> http://www.opensmiles.org
>
> Tim did a great deal of reformating with nice style sheets, and there is a
> whole new section on stereo centers.
>
I am very pleased to see progress on Open SMILES - the closed nature of
previous SMILES implementations has probably cost hundreds of millions of
dollars if not more in having incompatible information. Open specs are
critical and the Neelie Kroes in the EC is leading a very strong agenda on
OSS and standards.
"If you can build a molecule from a modeling kit, you can name it."
This is an interesting and largely true statement but with qualifications.
Names are categorial and discrete - geometry is often continuous. I agree
that Constitution - through graphs - seems to be largely discrete (but
breaks down where the existence of bonds is subjective or variable).
However Configuration can be continuous and Conformation frequently is. So
I'd argue that there should be a pragmatic line drawn - and it's mainly
that SMILES, InChI (which is isomorphic) and constitutional graphs start to
degrade when stepping outside mainstream organic chemistry.
Of the extensions my votes would be for:
* R-groups on static bonds (i.e. not to ring centres) - yes, we need this
* crystals - absolutely not. DW tried to do this without understanding
crystals. It can never work
* polymers - gets tricky very quickly. There are almost always some free
variables (n's and m's)
* twisted SMILES. Please No. Yes, it works for chair cyclohexane. Almost
everything else it gets messy very quickly. Geometry does not behave
prettily
Physical properties attached to molecules and parts of molecules. No. The
concept and the syntax aren't designed for this. InChI is in danger of
trying to canonicalize real numbers done by machines. It can't be done.
If you think this is too conservative, ask how you represent "Aluminium
Chloride".
P.
--
Peter Murray-Rust
Reader in Molecular Informatics
Unilever Centre, Dep. Of Chemistry
University of Cambridge
CB2 1EW, UK
+44-1223-763069
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