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Example: The XSLT stylesheet for this Atom feed generates a web page for each entry: http://news.dieweltistgarnichtso.net/notes/index.xml http://news.dieweltist

Example: The XSLT stylesheet for this Atom feed generates a web page for each entry: http://news.dieweltistgarnichtso.net/notes/index.xml http://news.dieweltistgarnichtso.net/notes/index.xml In this setup, the Atom XML for each entry is generated from XHTML with XSLT, which makes it possible to automatically include an Atom enclosure element for every XHTML media element. To publish a podcast episode, it is enough to add a post with an <audio> or <video> element, as an XSLT stylesheet can “reach into” the XHTML content. Namespaces are also widely used in SVG, which uses the XLink specification for hyperlinks and can embed XHTML and MathML content. Since SVG can be embedded in (X)HTML, this means you can have an ATOM feed containing XHTML containing MathML and SVG that contains XHTML and all have it displayed correctly.

lmm 10y ago
> Example: The XSLT stylesheet for this Atom feed generates a web page for each entry: http://news.dieweltistgarnichtso.net/notes/index.xml http://news.dieweltistgarnichtso.net/notes/index.xml > In this setup, the Atom XML for each entry is generated from XHTML with XSLT, which makes it possible to automatically include an Atom enclosure element for every XHTML media element. To publish a podcast episode, it is enough to add a post with an <audio> or <video> element. Sure. Why do you need namespaces to do that? Why couldn't you do it in XML-without-namespaces (or even JSON and some theoretical JSON-transformation-lanugage?) > Namespaces are also widely used in SVG, which uses the XLink specification for hyperlinks and can embed XHTML and MathML content. Again, why are namespaces necessary though? Why not just have a tag whose content is specified to be XHTML/MathML ? Wouldn't you want that anyway for the sake of human readability?
- erlehmann_ 10y ago
  XML without namespaces does not exist. If it existed, how would you differentiate between title and link elements in Atom and title and link elements in XHTML? They have the same element names, but do not have the same meaning and therefore must be processed differently. Namespaces ensure that any XML processor can know the language of each part of the input. Namespaces actually are the general mechanism with which you can specify that content is in another language: If you look at the feed source code, you can see that XHTML content is started with <div xmlns="http://www.w3.org/1999/xhtml"> http://www.w3.org/1999/xhtml"> and ends where that div element is closed. Having an element with the semantics that “this content is in another language” is done out of necessity in HTML, as it has no namespacing: <style> elements contain CSS, <script> elements contain JavaScript, <svg> elements contain SVG … having an element in each language to embed each other language would become complicated very fast.
  - lmm 10y ago
    > XML without namespaces does not exist. If it existed, how would you differentiate between title and link elements in Atom and title and link elements in XHTML? By where it is in the structure. The document is a tree where each element has well-defined context; there should never be confusion about whether a particular <title> is part of the feed or part of the content in the feed, because if it's in content it will be inside the content tag. (Don't you need to do that anyway? I mean what if the XHTML had another Atom feed embedded in it? Or the content of one of the entries in the feed was another Atom feed? That's legitimate, but you wouldn't want to show titles from the "inner" feed as titles in the feed). > Having an element with the semantics that “this content is in another language” is done out of necessity in HTML, as it has no namespacing: <style> elements contain CSS, <script> elements contain JavaScript, <svg> elements contain SVG … having an element in each language to embed each other language would become complicated very fast. Only if you need the ability to embed an arbitrary other language. And if you do need that you can't possibly be validating or transforming based on what's embedded, so what value is the namespacing of it giving you?
    - erlehmann_ 10y ago
      > The document is a tree where each element has well-defined context; there should never be confusion about whether a particular <title> is part of the feed or part of the content in the feed, because if it's in content it will be inside the content tag. In this specific case, maybe – but generally, it is not true that you can infer the namespace of an element from context. Also, elements can have multiple attributes with different namespaces (and often do). > I mean what if the XHTML had another Atom feed embedded in it? Or the content of one of the entries in the feed was another Atom feed? That's legitimate, but you wouldn't want to show titles from the "inner" feed as titles in the feed That actually appears to be a bug in my stylesheet. Thank you for bringing it to my attention! Programs often use namespaces to provide metadata. Here is an SVG I created with Inkscape that uses six different namespaces for metadata: http://daten.dieweltistgarnichtso.net/pics/icons/minetest/minetest-icon.svg http://daten.dieweltistgarnichtso.net/pics/icons/minetest/mi... Thanks to namespacing, web browsers can display the picture while ignoring Inkscape-specific data. > Only if you need the ability to embed an arbitrary other language. And if you do need that you can't possibly be validating or transforming based on what's embedded, so what value is the namespacing of it giving you? It is very useful to embed any arbitrary language, as XML processors can preserve the content they do not understand without processing it. My XSLT stylesheet would have no issue with SVG embedded in XHTML, just as your web browser most likely ignores everything about the SVG linked above it can not understand.

lmm 10y ago

> Example: The XSLT stylesheet for this Atom feed generates a web page for each entry: http://news.dieweltistgarnichtso.net/notes/index.xml http://news.dieweltistgarnichtso.net/notes/index.xml > In this setup, the Atom XML for each entry is generated from XHTML with XSLT, which makes it possible to automatically include an Atom enclosure element for every XHTML media element. To publish a podcast episode, it is enough to add a post with an <audio> or <video> element. Sure. Why do you need namespaces to do that? Why couldn't you do it in XML-without-namespaces (or even JSON and some theoretical JSON-transformation-lanugage?) > Namespaces are also widely used in SVG, which uses the XLink specification for hyperlinks and can embed XHTML and MathML content. Again, why are namespaces necessary though? Why not just have a tag whose content is specified to be XHTML/MathML ? Wouldn't you want that anyway for the sake of human readability?

erlehmann_ 10y ago
XML without namespaces does not exist. If it existed, how would you differentiate between title and link elements in Atom and title and link elements in XHTML? They have the same element names, but do not have the same meaning and therefore must be processed differently. Namespaces ensure that any XML processor can know the language of each part of the input. Namespaces actually are the general mechanism with which you can specify that content is in another language: If you look at the feed source code, you can see that XHTML content is started with <div xmlns="http://www.w3.org/1999/xhtml"> http://www.w3.org/1999/xhtml"> and ends where that div element is closed. Having an element with the semantics that “this content is in another language” is done out of necessity in HTML, as it has no namespacing: <style> elements contain CSS, <script> elements contain JavaScript, <svg> elements contain SVG … having an element in each language to embed each other language would become complicated very fast.
- lmm 10y ago
  > XML without namespaces does not exist. If it existed, how would you differentiate between title and link elements in Atom and title and link elements in XHTML? By where it is in the structure. The document is a tree where each element has well-defined context; there should never be confusion about whether a particular <title> is part of the feed or part of the content in the feed, because if it's in content it will be inside the content tag. (Don't you need to do that anyway? I mean what if the XHTML had another Atom feed embedded in it? Or the content of one of the entries in the feed was another Atom feed? That's legitimate, but you wouldn't want to show titles from the "inner" feed as titles in the feed). > Having an element with the semantics that “this content is in another language” is done out of necessity in HTML, as it has no namespacing: <style> elements contain CSS, <script> elements contain JavaScript, <svg> elements contain SVG … having an element in each language to embed each other language would become complicated very fast. Only if you need the ability to embed an arbitrary other language. And if you do need that you can't possibly be validating or transforming based on what's embedded, so what value is the namespacing of it giving you?
  - erlehmann_ 10y ago
    > The document is a tree where each element has well-defined context; there should never be confusion about whether a particular <title> is part of the feed or part of the content in the feed, because if it's in content it will be inside the content tag. In this specific case, maybe – but generally, it is not true that you can infer the namespace of an element from context. Also, elements can have multiple attributes with different namespaces (and often do). > I mean what if the XHTML had another Atom feed embedded in it? Or the content of one of the entries in the feed was another Atom feed? That's legitimate, but you wouldn't want to show titles from the "inner" feed as titles in the feed That actually appears to be a bug in my stylesheet. Thank you for bringing it to my attention! Programs often use namespaces to provide metadata. Here is an SVG I created with Inkscape that uses six different namespaces for metadata: http://daten.dieweltistgarnichtso.net/pics/icons/minetest/minetest-icon.svg http://daten.dieweltistgarnichtso.net/pics/icons/minetest/mi... Thanks to namespacing, web browsers can display the picture while ignoring Inkscape-specific data. > Only if you need the ability to embed an arbitrary other language. And if you do need that you can't possibly be validating or transforming based on what's embedded, so what value is the namespacing of it giving you? It is very useful to embed any arbitrary language, as XML processors can preserve the content they do not understand without processing it. My XSLT stylesheet would have no issue with SVG embedded in XHTML, just as your web browser most likely ignores everything about the SVG linked above it can not understand.