About Mapping Services › What Is Mapping Services?

What Is Mapping Services?

Mapping Services is a facility that provides NCL with enhanced capabilities for manipulating data with various formats.

Early versions of NCL stored program data only as tokens (or NCL variables). Mapping Services enhances NCL by introducing Mapped Data Objects (MDOs) as an alternative to tokens and as a means of storing data. Data can easily be transferred between MDOs and tokens. MDOs can also be written directly to files and are supported by a number of specialized NCL functions such as &ASSIGN and &APPC. MDOs can be used in many situations where tokens are used.

An MDO can contain any data that can be represented as a continuous string of bytes in storage. The primary advantage of an MDO over NCL tokens is that particular substructures within an MDO can be located and referenced by name from NCL, using various rules which Mapping Services understands. Various segments within these substructures can also be referenced. The substructures which can be referenced within MDO data are generically known as components.

To distinguish between various substructures which exist within a particular MDO, a unique tag or key is assigned to each component. To determine what names are to be associated with particular components within an MDO, and their tag values, a map is used. A map enables the NCL language to associate names with the various components which exist within a particular MDO. Thus a map provides NCL with the ability to interpret the data contained within an MDO.