What happens?

SpecificAssetIdsClause is defined as folllowing in the grammar:
<SpecificAssetIdsClause> ::= ( "specificAssetIds" ( "[" ( [0-9]* ) "]" )? ( ".name" | ".value" | ".externalSubjectId" | ".externalSubjectId." <ReferenceClause> ) )

Why is this wrong?

According to the current grammar not giving an index with brackets is possible e.g.: specificAssetIds.name.
This is wrong because it points to the not given attribute "name" of a list.

How should it be fixed?

The brackets must be mandatory.
Fixed grammar:
<SpecificAssetIdsClause> ::= ( "specificAssetIds" ( "[" ( [0-9]* ) "]" ) ( ".name" | ".value" | ".externalSubjectId" | ".externalSubjectId." <ReferenceClause> ) )

Other items to fix

The same should be done for the following clauses:

• FieldIdentifierAasDescriptor
  

  aas-specs-api/documentation/IDTA-01002-3/modules/ROOT/pages/grammar.adoc

  Line 204 in bbd9637

  <FieldIdentifierAasDescriptor> ::= "$aasdesc#" ( "idShort" | "id" | "assetKind" | "assetType" | "globalAssetId" | <SpecificAssetIdsClause> | "endpoints" ( "[" ( [0-9]* ) "]" )? "." <EndpointClause> | "submodelDescriptors" ( "[" ( [0-9]* ) "]" )? "." <SmDescriptorClause> )

• SmDescriptorClause
  

  aas-specs-api/documentation/IDTA-01002-3/modules/ROOT/pages/grammar.adoc

  Line 206 in bbd9637

  <SmDescriptorClause> ::= ( <SemanticIdClause> | "idShort" | "id" | "endpoints" ( "[" ( [0-9]* ) "]" )? "." <EndpointClause> )

• ReferenceClause
  

  aas-specs-api/documentation/IDTA-01002-3/modules/ROOT/pages/grammar.adoc

  Line 209 in bbd9637

  <ReferenceClause> ::= ( "type" | "keys" ( "[" ( [0-9]* ) "]" )? ( ".type" | ".value" ) )

• SpecificAssetIdsClause
  

  aas-specs-api/documentation/IDTA-01002-3/modules/ROOT/pages/grammar.adoc

  Line 211 in bbd9637

  <SpecificAssetIdsClause> ::= ( "specificAssetIds" ( "[" ( [0-9]* ) "]" )? ( ".name" | ".value" | ".externalSubjectId" | ".externalSubjectId." <ReferenceClause> ) )