The ISO 8211 FAQ has some good background on ISO 8211 formatted files. I will briefly introduce it here, with reference to the library classes representing the components. What fields appear on what records is not defined by ISO 8211, though more specific requirements may be implied by a particular data standard such as SDTS or S-57. Each field instance has a name, and consists of a series of subfields.
Some fields contain an array of their group of subfields.
For instance a coordinate field may have X and Y subfields, and they may repeat many times within one coordinate field indicating a series of points. The iso8211.h contains the definitions for all public ISO8211Lib classes, enumerations and other services. This will read the DDR, and establish all the DDFFieldDefn , and DDFSubfieldDefn objects which can be queried off the DDFModule . They can be queried with various DDFRecord methods. Note that there is no object instantiated for individual subfields of a DDFField .