Failing to meet integrity constraint S14 when terminology evolves

Dear All,

I have a problem in assigning labels to SKOS concepts within an evolving 
terminology, and am therefore looking for your opinions.

In the ICD 10 coding system, Germany version, the text assigned to a code 
changes between different versions, e.g.
in ICD10GM 2004, the code K12.23 has a label:Wangenabszeß
in ICD10GM 2013, the code K12.23 has a label:Wangenabszess

Before realizing the problem, I formalized the code as SKOS concept:
icd10gm:K12.23 a skos:concept;
        skos:prefLabel "Wangenabszeß"@de.
However, it ends up with 
icd10gm:K12.23 a skos:concept;
        skos:prefLabel "Wangenabszeß"@de;
        skos:prefLabel "Wangenabszess"@de. 
which is not consistent with the integrity constraint S14.

As the ICD 10 GM publish a new version each year, and most of the labels 
are stable, it also seems to be overkill to create a concept for each 
version, e.g.
icd10gm2004:K12.23 a skos:concept;
        skos:prefLabel "Wangenabszeß"@de.
and
icd10gm2013:K12.23 a skos:concept;
        skos:prefLabel "Wangenabszess"@de.

I also consider to take the labels from the latest version as prefLabel, 
and those from an older version as altLabel, e.g.
icd10gm:K12.23 a skos:concept;
        skos:prefLabel "Wangenabszess"@de; 
        skos:altLabel "Wangenabszeß"@de.
 
The problem for this approach is that in case the code changes in later 
versions(e.g. v2014), then the skos:prefLabel needs to be updated again. 
If the formalized terminology is already published, then such request to 
update will be a problem.

I currently planed to formalize the concept as below:
icd10gm:K12.23 a skos:concept;
        rdfs:label "Wangenabszess"@de; 
        rdfs:label "Wangenabszeß"@de.

Still not very satisfied with this solution yet. Is there any better 
solution with other SKOS properties? Meanwhile, is there a general 
principle/guideline for SKOS in formalizing (the labels) of an evolving 
terminology? Thanks!

Kind Regards,

Hong Sun | Agfa HealthCare
Researcher | HE/Advanced Clinical Applications Research
T  +32 3444 8108