Help page of the REST-API of the structure search engine of the 'Crystallography Open Database'

  (For Java clients there is a more efficient API that allows
   sending complex search specifications as single Java object)

To use the REST-API you may send HTTP GET or POST requests to one of
the mirrors running this service (e.g. cod.openmolecules.org).
You may attach key-value pairs as parameters to define your query:

key 'what':
  value 'help': Returns this help page as text.

  value 'query': Defines a structure query and requires more parameters:
    key 'smiles': Optional parameter to attach a structure search to the query.
      value: valid SMILES code of a chemical structure for substructure or similarity search.
        key 'searchType': optional parameter to define the search type. If not given, 'substructure' is assumed.
          value: Currently it must be 'substructure' or 'similarity'.
        key 'threshold' Optional numerical similarity cut-off. If not given '80' is assumed.
          value: numerical fractional or percent value, e.g. '0.75' or '75', to return all structures
                 with a higher similarity to the query structure than 75%.
    key 'organicOnly': Optional parameter to limit result structures to purely organic ones.
      value: 'true' or 'false' (default: 'false').
    key 'author': Optional parameter to attach an author restriction to the query (not case-sensitive).
      value: (part of a) name that must be a substring of the author field to qualify as search result.
    key 'year': Optional parameter to attach publication year restriction to the query.
      value: four digit number, leading '<' or '>' or ranges as '2002-2004' are accepted.

  value 'molfile2': Requests a COD structure to be returned in the molfile (version 2) format.
  value 'molfile3': Requests a COD structure to be returned in the molfile (version 3) format.
    key 'id': Mandatory parameter for molfile requests to identify a COD entry.
      value: A valid COD number. Note: A small fraction of the COD database is not available through this service.
             NOTE: Many metal-organic COD structures contain coordinate (dative) bonds,
                   which are not supported by the version 2 molfile standard.
                   This server (mis-)uses the ANY bond type to represent coordinate bonds in V2 molfiles.

Examples (as HTTP GET requests):
  http://cod.openmolecules.org/?what=help
    Get this help page.

  http://cod.openmolecules.org/?what=query&smiles=c1cncnc1OC
    Retrieve information about all COD entries that are a super-structure of 6-Methoxy-pyrimidines.

  http://cod.openmolecules.org/?what=query&author=reetz&year=1995-2000
    Retrieve all COD entries being published between 1995 and 2000 of which the author field contains 'reetz'.

  http://cod.openmolecules.org/?what=molfile3&id=4071641
    Retrieve the 3D-structure of the COD entry 4071641 as molfile (version 3).