Tagging and mapping is part of the automated process of receiving information. It is done once, and reused. Tagging and mapping allows you to extend taxonomies for new elements, labels, references, presentation and calculation arcs and domain member relationships.
Mapping is the association of data facts to elements.
The tagging process is a simple drag and drop.
Data facts are inventoried. All must be accounted for.
Data facts are either mapped or discarded, with explanation.

A convenient feature is the ability to extend taxonomies and map to the extension from one central utility.
The mapping program provides multiple functionalities from a centralized location.
These include extending elements, extending labels and references, creating presentation and calculation arcs and domain member relationships.

Best practice is to use existing elements whenever possible.
Labels should be extended to display text exactly as it appears on your company statements.

If you extend for a new element and that element is a debit/credit, you may want to include the data associated with that element into an existing calculation within the taxonomy.
Snappy Reports allows you to drag elements to each other and simply choose either add or subtract.
If you extend for a new element, you are going to want to position it properly within the report.
XBRL defines this as presentation arcs.
Snappy Reports creates arcs implicitly when you drag and drop objects into place.

Elements whose value is the result of a calculation are denoted by a
Elements added in are displayed in yellow, elements subtracted display in gray.

A domain member relationship is the relationship of elements in terms of their data. Most taxonomies define domain member relationships. If you extend for a new element, you may want to include your new element in an existing domain member relationship.

Domain member relationships are displayed by clicking on a domain object.
Associated members are displayed in blue.

Mapping is a simple as dragging data concepts from the right side of the screen to elements displayed to the left.
Snappy Reports allows you to document each mapping. Documentation explains to others the reasoning for mapping choices made.
Mapping is persistent. Map only once and you are done.

Snappy Reports XBRL uses icons to denote object types.