[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

Weird XML rules

• From: Roger L Costello <costello@mitre.org>
• To: "xml-dev@lists.xml.org" <xml-dev@lists.xml.org>
• Date: Sat, 19 Mar 2022 13:45:36 +0000

On Thursday, Liam Quin wrote:

> numeric character references are always treated as data when they are read, not markup.

If the word "numeric" is removed from that sentence does the sentence still hold true? That is, _all_ character references are treated as data, not markup. True? For example, just as the numeric character reference < is always treated as data, so too the XML character reference < is always treated as data. What that means is:

<Test foo="&#x3C;"/>
<Test foo="&lt;"/>

are both legal. 

To an XML-aware tool, the following all denote the same character. More precisely, they all denote the same code point.

<
&lt;
&#x3C;
&#x3c;
&#x60;

And yet, they are treated differently:

< is illegal in an attribute value because < is treated as markup. But the entity versions are legal in an attribute value because they are treated as data.

< is illegal in an element value because < is treated as markup. But the entity versions are legal in an element value because they are treated as data.

Is this correct?

So, the same character is treated differently purely because of the way the character is lexically represented.

Isn't that weird?

Is there ever a case where an entity version is not treated as data; rather, it is treated as markup?

/Roger

• Follow-Ups:
  • Re: Weird XML rules
    • From: David Carlisle <d.p.carlisle@gmail.com>
  • Re: Weird XML rules
    • From: Michael Kay <mike@saxonica.com>
  • Re: Weird XML rules
    • From: David Carlisle <d.p.carlisle@gmail.com>