Import simple NodeSet2 file is incomplete #510

- added SemanticData/BuildingErrorsHandling/IIdentifierSyntax.md to formaly define syntax of the build errors.
- no code changes

SemanticData/BuildingErrorsHandling/IIdentifierSyntax.md

@@ -0,0 +1,49 @@
+# BuildError.Identifier syntax
+
+## ABNF
+
+``` TXT
+
+Identyfier = Part - Section Number
+Part = Prefix 2DIGIT
+Prefix = "P"
+Section = 8DIGIT
+Number = 2DIGIT
+
+```
+
+where:
+
+| Rule    | Meaning            | Syntax                                               |
+| ------- | ------------------ | ---------------------------------------------------- |
+| Prefix  |                    | matches the character `P` literally (case sensitive) |
+| Part    | OPC UA part number | matches a digit (equal to [0-9]) exactly 2 times     |
+| Section | section number     | matches a digit (equal to [0-9]) exactly 8 times     |
+| Number  | sequential number  | matches a digit (equal to [0-9]) exactly 2 times     |
+
+## Reqular expresion
+
+`(P\d{2,2})-(\d{8,8})(\d{2,2})`
+
+where:
+
+- `Part`: OPC UA part number; 1st Capturing Group (P\d{2,2})
+  - `P` matches the character `P` literally (case sensitive)
+  - `\d{2,2}` matches a digit (equal to [0-9])
+    - {2,2} Quantifier — Matches exactly 2 times
+- `-` matches the character `-` literally (case sensitive)
+- `Section`: section number; 2nd Capturing Group (\d{8,8})
+  - `\d{8,8}` matches a digit (equal to [0-9])
+    - {8,8} Quantifier — Matches exactly 8 times
+- `Number`: sequential number; 3rd Capturing Group (\d{2,2})
+  - \d{2,2} matches a digit (equal to [0-9])
+    - {2,2} Quantifier — Matches exactly 2 times
+
+## Example
+
+- [P3-0503030201](https://reference.opcfoundation.org/v104/Core/docs/Part3/#5.3.3.2)
+
+## See also
+
+- [Augmented BNF for Syntax Specifications: ABNF; RFC5234; 2008](https://tools.ietf.org/html/rfc5234)
+- [Regular expression; From Wikipedia, the free encyclopedia](https://en.wikipedia.org/wiki/Regular_expression)