# Defining the scope of the map

Prior to building the map, it’s important to define the scope, processes and mapping rules to have consistency between all personnel involved. These should be documented clearly and updated frequently as required.

The scope of a map is tightly bound to the map's use case and purpose. Once the use case and the purpose has been defined, the scope of the source and target code systems of the map can then be defined.

When defining the scope of the source and target code systems of the map, consider the following:

{% columns %}
{% column width="25%" %}
**What is the scope of the source code system?**
{% endcolumn %}

{% column width="75%" %}
Does the whole source code system need to be mapped, or is a subset sufficient?

If it is a historical code system, is the subset of codes that have been used in practice sufficient?

Is there a need to map historical or inactive terms?

Is there a need to exclude some terms if ambiguous, duplicates, not within the required scope?
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column width="25%" %}
**How is the source code system used in the implementation?**
{% endcolumn %}

{% column width="75%" %}
Is the source code system appropriate for the data model it was implemented in?

What is the meaning of the codes in the context of the data model?
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column width="25%" %}
**How will the map targets be implemented?**
{% endcolumn %}

{% column width="75%" %}
Is the target source code system appropriate for the new data model?
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column width="25%" %}
**What is the scope of the target source code system?**
{% endcolumn %}

{% column width="75%" %}
Is the whole target code system appropriate or is a subset more appropriate?
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column width="25%" %}
**Are the scopes of the source and target code systems compatible?**
{% endcolumn %}

{% column width="75%" %}
Do they match? Should they match?

Requirements for exclusions or specific rules about how the scopes will be translated.

Is there need for contextual information (e.g. from the information model) to be included in the decision for what the map target should be

If mapping from a source code system for a "Family History" field (source) to a new data model that was an "Other information" field (target) then *|A123 Breast cancer|* in a Family History field may need a map to a single term like *429740004 |Family history of malignant neoplasm of breast|*

At what level do the terms need to be mapped? Is equivalence the goal, or are we grouping things to a broader target? This will be determined by the use case.
{% endcolumn %}
{% endcolumns %}

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