phenomenon · claim-type · cross-domain-transfer · mechanism · claim-relation · replication-status · limitation — grounded in the full text| phenomenon | the proliferation of incompatible chemical file formats, which a standard failed to resolve— “While attempts have been made to provide a standard format for storing chemical data, including most notably the development of Chemical Markup Language (CML) [2-6], an XML dialect, such formats have not yet achieved widespread use.” | |
| claim-type | method— “With the release of Open Babel 2.3, Open Babel supports 111 chemical file formats in total. It can read 82 formats and write 85 formats.” | |
| method — evidence | — “Starting with a dataset of 18,084 3D structures from PubChem3D as an SDF file, we compared the result of (a) conversion to SMILES, followed by conversion of that to Canonical SMILES to (b) conversion directly to Canonical SMILES.” | |
| object of study — evidence | — “With the release of Open Babel 2.3, Open Babel supports 111 chemical file formats in total. It can read 82 formats and write 85 formats.” | |
| research question — evidence | — “A frequent problem in computational modeling is the interconversion of chemical structures between different formats.” | |
| contribution — evidence | — “At the time of starting this work (March 2009), the error rate found was 1424 (8%); by Oct 2009, combined work on stereochemistry, kekulization and canonicalization had reduced this to 190 (~1%), and continued improvements have reduced the number of errors down to two (shown in Figure 4) for Open Babel 2.3.1 (~0.01%).” | |
| mechanism | BOND CONNECTIVITY FROM GEOMETRY ALONE: atoms closer than the sum of their covalent radii plus 0.45 angstrom are bonded, which is what lets formats that store no bonding at all be read as molecules— “Bond connectivity is determined by the frequently used algorithm of detecting atoms closer than the sum of their covalent radii, with a slight tolerance (0.45 Å) to allow for longer than typical bonds.” | mechanisms[0] |
| mechanism | AROMATICITY IS WITHHELD UNLESS A KEKULE PATTERN EXISTS: the ring is only called aromatic when a well-defined valence-bond assignment can be found, so the label is earned by a construction rather than asserted from ring membership— “Aromaticity is established only if a well-defined valence bond Kekulé pattern can be determined.” | mechanisms[1] |
| mechanism | AN EXPONENTIAL SEARCH WITH A DELIBERATE GIVE-UP: kekulisation terminates at 30 levels of recursion or 15 seconds, so a large fused ring system returns no answer rather than hanging— “Since this process is exponential in complexity, the algorithm will terminate if more than 30 levels of recursion or 15 seconds are exceeded (which may occur in the case of large fused ring systems such as carbon nanotubes).” | mechanisms[2] |
| mechanism | SUBSTRUCTURE SEARCH BY HASHED BIT-STRING: every linear and ring substructure of length 1 to 7 is mapped onto 1024 bits, so a query's bits must all be set in any target that contains it— “This fingerprint, referred to as FP2 in Open Babel, identifies all linear and ring substructures in the molecule of lengths 1 to 7 (excluding the 1-atom substructures C and N) and maps them onto a bit-string of length 1024 using a hash function.” | mechanisms[3] |
| sense | canonical representation - A CHOICE, NOT A FACT ABOUT THE MOLECULE: the same structure has N! orderings that encode exactly the same information, and canonicalisation picks one so it can be used as a database key— “While each of the orderings encodes exactly the same information, it can be useful to define a canonical numbering of the atoms of a molecule and use this to derive a canonical representation of a molecule for a particular file format.” | senses[0] |
| sense | failure - IN THIS PAPER A ROUND-TRIP DISAGREEMENT, not a wrong answer: two routes to the same canonical SMILES are compared against each other, and the second of the two residual failures is a case where BOTH strings are correct and the algorithm merely failed to choose— “The second failure involves confusion over the canonical stereochemistry at a bridgehead carbon” | senses[1] |
| control | a round-trip over 18,084 PubChem3D structures: SDF to SMILES to canonical SMILES, compared against SDF straight to canonical SMILES — held — rules out errors anywhere in reading SDF, reading and writing SMILES, and canonicalisation - by making two routes to the same answer disagree— “Starting with a dataset of 18,084 3D structures from PubChem3D as an SDF file, we compared the result of (a) conversion to SMILES, followed by conversion of that to Canonical SMILES to (b) conversion directly to Canonical SMILES.” | controls[0] |
| control | a nightly test suite of 60 programs, each with tens to hundreds of tests — held — rules out regressions between releases— “Open Babel includes an extensive test suite comprising 60 different test programs each with tens to hundreds of tests.” | controls[1] |
| edge | Chemical Markup Language —is-a→ XML dialect— “While attempts have been made to provide a standard format for storing chemical data, including most notably the development of Chemical Markup Language (CML) [2-6], an XML dialect, such formats have not yet achieved widespread use.” | concept_edges[0] |
| edge | structural similarity —operationalised-as→ Tanimoto coefficient— “The fingerprints for two molecules can also be used to calculate structural similarity using the Tanimoto coefficient, the number of bits in common divided by the union of the bits set.” | concept_edges[2] |
| outcome (stated by the tagger, no quotation) | control — held | controls[0] |
| outcome (stated by the tagger, no quotation) | control — held | controls[1] |
| limitation | TWO round-trip failures remain at 0.01%, and the paper names both: a kekulisation error in a polycyclic aromatic with heteroatoms, and a bridgehead-carbon stereochemistry case— “At the time of starting this work (March 2009), the error rate found was 1424 (8%); by Oct 2009, combined work on stereochemistry, kekulization and canonicalization had reduced this to 190 (~1%), and continued improvements have reduced the number of errors down to two (shown in Figure 4) for Open Babel 2.3.1 (~0.01%).” | limitations[0] |
| limitation | Molecules outside the pharmaceutical mainstream - radicals, organometallics, inorganics, coordinate and 3-center 2-electron bonds - are stated to be poorly supported, and not only by this toolkit— “Typically toolkits focus on the types of molecules of principal importance to the pharmaceutical industry, namely stable organic molecules comprising wholly of 2-center 2-electron covalent bonds. Molecules outside this set - such as radicals, organometallic and inorganic molecules, molecules with coordinate bonds or 3-center 2-electron bonds… | limitations[1] |
| limitation | Kekulisation is exponential and is CUT OFF at 30 levels of recursion or 15 seconds, so large fused ring systems are a known non-answer— “Since this process is exponential in complexity, the algorithm will terminate if more than 30 levels of recursion or 15 seconds are exceeded (which may occur in the case of large fused ring systems such as carbon nanotubes).” | limitations[2] |
| limitation | The standard that was meant to remove the problem did not take: CML exists and is not widely used, which is the premise the whole toolkit rests on— “While attempts have been made to provide a standard format for storing chemical data, including most notably the development of Chemical Markup Language (CML) [2-6], an XML dialect, such formats have not yet achieved widespread use.” | limitations[3] |
| concept | Open Babel— “With the release of Open Babel 2.3, Open Babel supports 111 chemical file formats in total. It can read 82 formats and write 85 formats.” | concepts[0] |
| concept | interconversion— “A frequent problem in computational modeling is the interconversion of chemical structures between different formats.” | concepts[1] |
| concept | Chemical Markup Language— “While attempts have been made to provide a standard format for storing chemical data, including most notably the development of Chemical Markup Language (CML) [2-6], an XML dialect, such formats have not yet achieved widespread use.” | concepts[2] |
| concept | canonical representation | concepts[3] |
| concept | canonical numbering | concepts[4] |
| concept | canonicalization Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[5] |
| concept | kekulization Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[6] |
| concept | stereochemistry Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[7] |
| concept | aromaticity Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[8] |
| concept | covalent radii Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[9] |
| concept | Tanimoto coefficient Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[10] |
| concept | substructures Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[11] |
| concept | structural similarity Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[12] |
| concept | XML dialect Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[13] |
| concept | SMILES Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[14] |
| concept | test suite Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[15] |
| concept | OELib Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[16] |
| concept | OEChem Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[17] |
| concept | file formats Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[18] |
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