> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-ct-practical-guides/snomed-ct-mapping-guide/developing-use-case-and-requirements/5.3.1-defining-the-scope-of-the-map.md).

# Defining the scope of the map

Prior to building the map, it’s important to define the scope, processes, and mapping rules to ensure consistency among 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 purpose have been defined, the scope of the map's source and target code systems can be determined.

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

{% columns %}
{% column width="33.33333333333333%" %}
**What is the scope of the source code system?**
{% endcolumn %}

{% column width="66.66666666666667%" %}
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 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, or not within the required scope?
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column width="33.33333333333333%" %}
**How is the source code system used in the implementation?**
{% endcolumn %}

{% column width="66.66666666666667%" %}
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="33.33333333333333%" %}
**How will the map targets be implemented?**
{% endcolumn %}

{% column width="66.66666666666667%" %}
Is the target source code system appropriate for the new data model?
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column width="33.33333333333333%" %}
**What is the scope of the target source code system?**
{% endcolumn %}

{% column width="66.66666666666667%" %}
Is the whole target code system appropriate, or is a subset more appropriate?
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column width="33.33333333333333%" %}
**Are the scopes of the source and target code systems compatible?**
{% endcolumn %}

{% column width="66.66666666666667%" %}
Do they match? Should they match?

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

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

For example, if mapping from the source code system's "Family History" field, then the code 'A123 Breast cancer', when recorded in this field, may need to target a pre-coordinated concept, such as 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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