NET/MASTER Network Control Language (NCL) Programmer's Guide

The Structure of Mapped Data Object (MDO) Variables
Working With Mapping Services
10–6 106160 Tandem Computers Incorporated
The Structure of
Mapped Data Object
(MDO) Variables
The data item described by a map is stored in an MDO variable. In general, an MDO
variable consists of a header and a single data structure, called an element, where an
element consists of a header followed by a data component. The data component may
consist of other (enclosed) elements inside an outer (enclosing) element or other data
structures called groups and fields. Some enclosed elements can be repeated and are
called repeated elements. Data can be fixed or can vary in length.
This subsection discusses the structure of MDO variables and how to access the data
contained in MDO variables from an NCL procedure. This subsection examines the
following topics:
The header of an MDO variable:
The length field
The key field
Referring to a whole MDO variable from NCL
Elements in an MDO variable
The header of an element:
The length field
The key field
Referring to an element from NCL
The data component of an element (and how to access data from NCL):
Enclosing and enclosed elements
Repeated elements
Fixed length data sections
Variable length data sections
Groups in elements
Fields in elements
Enumerated data types