Mapping Services Facility › Defining the Physical Structure of Data › Local Form

Local Form

The definitions required to support the physical representation of data are not part of the defined ASN.1 language. This is because ASN.1 does not define how data ought to be represented, but only its abstract syntax. An implementation of ASN.1 represents data in a local form that is convenient for subsequent processing in the local environment.

This allows the physical representation, and hence the local form, to be customized, and subsequently ensures that the data conforms to this defined view.

To allow the customization of local form data, the ASN.1 Compiler recognizes a sequence of characters (which by definition are comments to ASN.1) and interprets the contents as implementation specific directives. It is these directives that can be used to instruct Mapping Services on the physical nature of the underlying data.