Is it oke to use - in an xml element name? e.g.
<rank-type>Rank</rank-type>
+2
A:
Yes, it is. But your example shows element name, not attribute-name. Which is also valid.
Michael Krelin - hacker
2009-09-25 17:08:09
+1
A:
That's not an attribute name, but an element name.
In any case - is supported for both attribute and element names in the spec as long as the name doesn't start with it (<-foo> is not a valid element name).
Some software might choke on it though, so be warned. If you have to use such software try to find better software or to make it's developers support the XML spec properly.
W3CSchools' (polemic) recommendations
Make names descriptive. Names with an underscore separator are nice: <first_name>, <last_name>.
Names should be short and simple, like this: <book_title> not like this: <the_title_of_the_book>.
Avoid "-" characters. If you name something "first-name," some software may think you want to subtract name from first.
Avoid "." characters. If you name something "first.name," some software may think that "name" is a property of the object "first."
Avoid ":" characters. Colons are reserved to be used for something called namespaces (more later).
XML documents often have a corresponding database. A good practice is to use the naming rules of your database for the elements in the XML documents.
Non-English letters like éòá are perfectly legal in XML, but watch out for problems if your software vendor doesn't support them.
Vinko Vrsalovic
2009-09-25 17:08:54
So, `<first_name />` is a nice element name and `<xsl:value-of />` is not?
Michael Krelin - hacker
2009-09-25 17:11:27
They are both valid. I'm assuming that the question may have a cause in some incident he's had with a -. That cause might be faulty software.
Vinko Vrsalovic
2009-09-25 17:13:48
Vinko, I said "nice", not "valid". I think it's funny when `w3cschools` accuse `w3c` of using worst practices ;-) And *personally* for œsthetic reasons, I'm on `w3c` side.
Michael Krelin - hacker
2009-09-25 17:16:34
I've now clarified the meaning.
Vinko Vrsalovic
2009-09-25 17:17:04
I personally find no element or attribute name "nice". I mind only about validity and practicality. And it may be impractical if you are stuck with a lousy library.
Vinko Vrsalovic
2009-09-25 17:20:41
It was not your fault, anyway. But I wouldn't link this resource and would call it as a sensible advice (as long as it's explained), but never best practice.
Michael Krelin - hacker
2009-09-25 17:22:09
Vinko, the word "nice" is taken from your quote. But wouldn't being stuck with lousy library by impractical? ;-)
Michael Krelin - hacker
2009-09-25 17:23:18
So the best practice in the case of having a lousy tool is to ignore reality and use the damned dash anyway? (You can't always change or fix the tools)
Vinko Vrsalovic
2009-09-25 17:24:48
Go talk to the authors of the quote about the names' niceness or lack thereof :).
Vinko Vrsalovic
2009-09-25 17:27:19
Vinko, you represent them ;-) And no, I think the best practice would be first to see if you have lousy tools, then to see if you can change it and then submit to using awful underscores all over the place ;-)
Michael Krelin - hacker
2009-09-25 17:31:50
Okay, that makes sense. Will adjust the answer.
Vinko Vrsalovic
2009-09-25 17:34:28
But you never again say I represent them. I merely quoted them.
Vinko Vrsalovic
2009-09-25 17:34:59
That's how you took responsibility. But true, adjusting the link's wording does change things.
Michael Krelin - hacker
2009-09-25 17:44:10
+1 to make up for a rather unfair -1. Your advice was sensible if not fully [pedentically] exacting...
mjv
2009-09-25 17:48:23
+2
A:
As readily stated by Vinko and hacker, the answer is
Yes, dashes are allowed in names, whether for element names or attribute names. However a dash cannot be the first character in the name.
The W3C standard defines the 'regular expression' for names as follow (section 2.3)
NameStartChar ::= ":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF] | [#x200C-#x200D] | [#x2070-#x218F] | [#x2C00-#x2FEF] | [#x3001-#xD7FF] | [#xF900-#xFDCF] | [#xFDF0-#xFFFD] | [#x10000-#xEFFFF]
NameChar ::= NameStartChar | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] | [#x203F-#x2040]
Name ::= NameStartChar (NameChar)*
Ignoring the various extended ASCII charactes and double-byte characters (which starting with # sign in the syntax definition), a name needs to start with an upper or lower case letter (A-Z), a colon (:) or an underscore. The characters following this start character, if any, i.e. if the name is not a single character, can be any of the valid start characters and/or any of the digits (0-9), the famous dash (-) and the dot (.)
As pointed out in the other responses, where possible, it is advisable to avoid certain characters, even though they may be legal, lest we risk encountering some implementation specific difficulties with various parsers and interop layers.
The W3C itself has implicitly vindicated the use of dashes as these are extensively used in XSL for example.
mjv
2009-09-25 17:32:54