> 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-specifications/snomed-ct-compositional-grammar-specification/implementation-guidance/7.7-classifying.md).

# Classifying

In order to automatically understand the inferred relationships between SNOMED CT expressions and/or precoordinated concepts, the expressions should be classified using a semantic reasoner. A number of reasoners exist, such as Snorocket, ELK and FACT++, which can classify and reason over OWL 2 EL.

Before a SNOMED CT compositional grammar expression can be classified using one of these reasoners, it must first be parsed, normalised and then translated into OWL 2 EL. The specific normalisation transformations that are required prior to translation into OWL include:

* Grouping all ungrouped attributes with a relationship type that is allowed to be grouped, and
* Transforming expressions to ensure that they conform to the concept model – in particular, where a laterality refinement has been applied to a focus concept that is not subsumed by [123037004 | Body structure|](http://snomed.info/id/123037004) , apply this laterality to all lateralisable finding sites within the definition of this focus concept.

The translation into OWL can then be performed in a variety of programming languages, including Perl.

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