Atom-Type Description Language: a universal language to recognize atom types implemented in the VEGA program

The atom-type description language (ATDL) is a universal language used to describe and recognize the atom types from chemical connectivity. In this paper the ATDL approach specifications are reported with several examples. To date, this language is implemented in VEGA (http://www.ddl.unimi.it), a multipurpose program able to convert and manage several molecular file formats. This software uses the ATDL to assign the correct atom types in order to help several functions (file format conversion, molecular properties calculation, surface mapping and interaction energy analysis).