AASd-002: wrong Regex pattern in documentation - or: support 1-character idShorts

[Frosty2500]

Both in the change log and in referabel attributes two different wrong RegEx patterns are given as examples. From the textual description a should be a valid id-short. But it does not fit any of the two patterns. An example of a RegEx pattern that fits the textual description is ^[a-zA-Z]|[a-zA-Z][a-zA-Z0-9_-]*[a-zA-Z0-9_]$.

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[sebbader-sap]

You are correct, the proposed regex pattern is better. I am moving this issue to the metamodel repository, as the change has to be implemented there first.

[sebbader-sap]

@BirgitBoss @s-heppner for your information

[s-heppner]

Indeed, the old regex

^[a-zA-Z][a-zA-Z0-9_-]*[a-zA-Z0-9_]+$

did not consider the edge case of "single character idShort".

The newly provided one:

^[a-zA-Z]|[a-zA-Z][a-zA-Z0-9_-]*[a-zA-Z0-9_]$

Says either one single character: ^[a-zA-Z] or a series of characters, hyphens and underscores, starting with a character and not ending with an underscore: [a-zA-Z][a-zA-Z0-9_-]*[a-zA-Z0-9_]$ (what we already had implemented in aas-core-meta and therefore in the schemas)
The new regex is therefore more precise to what is in the written text. (Though this makes me wonder why we specifically allow ending an idShort with a hyphen "-"?)

There are now 2 issues:

1. Changelog and Spec do not show the same regex (A simple oversight and therefore a bug)
2. Should we change the regex in the schema files as well? (Loosens what we currently allow in the schemas, so should be backward compatible in theory).

Regarding 2, there might be technical limitations. I don't recall precisely anymore, but I think there something about not being able to use "or" | in regular expressions for some languages? I think we encountered some issue there with XSD once.

[Frosty2500]

@s-heppner i think you meant to say that we don't allow ending with a hyphen and are asking why we allow ending an idShort with an underscore.

[BirgitBoss]

a was not a valid idShort: we decided that an idShort should have at least two characters.

For "x", "y", "z" axles we wanted to change this (but probably the issue was missing to change the constraint), but originally a minimum two-character idShort was really the goal!

" why we allow ending an idShort with an underscore.": easy reason, only because of backward compatibility to V3.0

So it is not a bug but a change request.

Of course we could also improve the description not mentioning that it shall have at least two characters.
Constraint AASd-002: [idShort](https://industrialdigitaltwin.io/aas-specifications/IDTA-01001/v3.1.2/spec-metamodel/common.html#Referable) of [Referable](https://industrialdigitaltwin.io/aas-specifications/IDTA-01001/v3.1.2/spec-metamodel/common.html#Referable)s shall consist of at least two characters and shall only feature letters, digits, hyphen ("-") and underscore ("_"); starting mandatory with a letter, and not ending with a hyphen, i.e. ^[a-zA-Z][a-zA-Z0-9_-]*[a-zA-Z0-9_]+$.

P.S. Yes, changelog looks a little bit strange [a-zA-Z][a-zA-Z0-9-]*[a-zA-Z0-9_]+$.], the ] at the end is wrong.

[Frosty2500]

So what needs to be updated is the minimum length of NameType? Or a new constraint has to be added/the textual description has to be changed

[BirgitBoss]

So what needs to be updated is the minimum length of NameType? Or a new constraint has to be added/the textual description has to be changed

Two alternatives:

1. improve textual description of constraints (in V3.2, no bugfix release needed since schema ok)
2. relax existing constraints to also allow 1-character values for idShort (new requirement for V3.2

and

• improve changelog description