Purpose of ditamap files

DITA map files are used for defining the topics of a publication, specifying the topic sequence, and controlling linking between topics.

DITA map (or ditamap) files have three primary purposes:
Topic Manifest
To define the topics to be processed into the output publication.
Hierarchy Definition
To define the sequence and hierarchy of topics in the output so that the heading levels, table of contents, parent-child links, and other navigation pathways (such as breadcrumb links) can be constructed.
Linking Relationships
To define the relationships between topics so that related topics links and other context-specific links can be automatically constructed.

A map has two main components: the hierarchy (of which there is one per map), and the relationship table (of which there can be none or many). Both are primarily made of topic references (topicref elements).

A ditamap file is not a topic: it contains no content. It is, however, a type of DITA XML file. A ditamap file can also contain publication- or output-specific metadata.

You can create as many ditamaps as you need. For example, you might create one map file for your Supara Impress XRW Owner's Manual, another for the Supara Impress XR Owner's Manual, and another for the Supara Impress Web site.