SMIRKS standardize function

The standardize function checks whether any smirks in the std smirks table, when used in the xform function, results in a modification of the input SMILES stored in NEW.smiles. If the xform function does return a transformed SMILES, then that transformed value is used in place of the value the user attempted to insert. Finally, the trigger is created using the standardized function to possibly modify any SMILE before inserting or updating a table. 

The use of Simplified Molecular Input Line Entry System (SMILES) as a string representation of chemical structure makes possible much of what has been discussed in earlier chapters of this book. A chemical reaction could be represented as a collection of SMILES, some identified as reactants and some as products. It is possible to define a table to do this, or perhaps use some arrays of character data types, but a syntax extension of standard SMILES allows reaction to be expressed easily. SMIRKS is an extension of SMILES and SMiles ARbitrary Target Specification (SMARTS). It is used to represent chemical transformations. SMIRKS can also be used in a transformation function to combine SMILES reactants to produce SMILES products. 

Suppose it is decided that the valence 5, noncharge-separated representation of the nitro group is to be used throughout the database. The SMIRKS [0 2]=[N+ 1][0- 3] [0 2]=[N+0 1]=[0+0 3], when applied to any charge-separated nitro group will transform it into the proper form. This is accomplished by creating another new SQL function, xform(smiles, smarts). As with the cansmiles and matches functions, this is an extension to standard SQL. Some form of this transformation function is... 

The std smirks table would contain the standard transformations. Chapter 9 shows a sample table of standard SMIRKS transformations. This table could be expanded at any time to include more standardizations as they become necessary without having to modify the trigger function to deal with these additions. 

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See also in sourсe #XX -- [ ]

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