948   Enumeration (string) values format

Created: 16 Nov 2012

Status: In Force (green)

Part: Part 7-1 (2011; Edition 2)

Links:

Page:

Clause: 14

Paragraph:

Category: Issue may impact interoperability of implementations of Edition 2

Issue

There are no rules specified for enumeration (string) values, either private (vendor-specific) or from other domains (e.g., wind, hydro...).

Part 6 (SCL schema) only enforces that the string value is unique within an EnumType and that its value is a "normalizedString", i.e., that it cannot contain line feed, carriage return, nor tab. There is no maximal length specified.

Besides UML modeling issues, "bizarre" enumeration types also affect tools (XML readers typically have issues with "&", "<", ">", quote, apostrophe).

Proposal

Enumeration (string) values should not be a description, but a literal/human-readable identifier.

For any new enumeration type a guideline shall be defined:
- max length; proposal: 127 or even less.
- allowed characters; proposal: ideally limit to basic latin character set (ASCI 127), but only letters (a-z, A-Z) without accents, digits (0-9), and the underscore.

At least, the following characters shall be forbidden (I think they are not used in any existing 61840 enumeration):
- double quotation mark (")
- ampersand (&)
- apostrophe (')
- less than (<)
- greater than (>)
(these characters correspond to XML "predefined entities").

As many of those constraints as possible shall be enforced in the SCL schema.

Discussion Created Status
Note that, contrary to the proposal, the solution is been included in the part 7-2 Edition 2.1 and that the tissue is still category InterOp 15 Jan 16 In Force (green)
13 Jan 16 In Force (green)
26 Oct 15 Ballot Period
Decision from SCL core team:
- enumeration string shall be limited to 127 characters (can be empty)
- enumeration string shall contain only characters from Basic-Latin and Latin-1-Supplement.

This shall be implemented in SCL and described in Part 6. No change to 7-1 (7-2) required.
26 Oct 15 Discussion (red)
7-3 already uses more than the propose character set (², ³, /, ...). There is no need for defining such a restriction now, that would not be aligned with the actual enumerations.
Additionally, <, >, <<, >> could be usefull in the protection environement, so I would not exclude neither the ", &, ', <, >
Those special characters are know as XML Entyties and MUST be supported by every XML compliant tool (see W3C All XML processors MUST recognize these entities whether they are declared or not.).
Therefore I'm not in favor of accepting the proposal.
16 Jan 13 Discussion (red)
10 Jan 13 Discussion (red)
This is not quite true. If we agree on restricting the character set for enumeration values, then the SCl schema can enforce this. However the general decision must be done in part 7 (-1, -2?). 17 Dec 12 Discussion (red)
This tissue, especially regarding the XML issue, belongs to 61850-6 and not to 7-1. 11 Dec 12 Future Improvement

 

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