When referencing an MDO in an NCL procedure, Mapping Services validates that the named component is defined (according to the name hierarchy supplied), and that the data within the component is valid, according to its underlying ASN.1 type. Each ASN.1 type can contain only certain valid values. Mapping Services checks the data value when retrieving data from, or assigning data into, an MDO. An operation attempting to retrieve or assign invalid data is rejected by Mapping Services with a feedback indicating type check.
In order to perform type checking Mapping Services first determines the base ASN.1 type of the component. Where a component is of a user defined type, the base ASN.1 type of the user defined type is inherited by the component. It is possible to have a number of levels of indirection between a user defined type and its base ASN.1 type.
The valid NCL values allowed for each of the base ASN.1 types is termed the external form. In addition to the set of valid values for each type, a specific component can be further constrained in what values are acceptable. Such constraints can be the result of either ASN.1 definitions or compiler directives. Finally, when data representing a valid NCL value is accepted for a component update, it is subject to a transformation from external form to local form, which is the MDO internal representation of data. This process can carry with it further constraints.
The valid external form values, and the behavior of data managed by Mapping Services, is described for each type in the following sections.
Notes: