> 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/evaluating-mapping-as-a-solution/4.3-compatibility-of-source-and-target-code-systems.md).
# Compatibility of source and target code systems
Mapping can be a bridge between two different code systems, but the prerequisite is that the two code systems being mapped have compatible semantic domains.
The semantic meaning of a concept or code can be made up of a combination of
* the representation in the code system, e.g. the description associated with a code
* the meaning provided by its structural representation in the code system, e.g. attributes inherent in the modelling within the code system
* the context of use, e.g. the clinical information model or clinical workflow
Prior to mapping, it is important to understand these points and assess the compatibility of the two code systems. Where the two code systems do not have compatible semantic domains, it may not be possible to build a meaningful or useful map.
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