What is meaning of "xmlns:v=urn:schemas-microsoft-com" in HTML5
html, xml
Solution
The xmlns:* attributes are namespace definitions. Elements and attributes with the prefix/alias "v" or "o" are part of the respective namespace and not part of HTML. If parsed as HTML < 5 the namespaces will be ignored. In HTML 5 here some constructs for specific namespaces (SVG, MathML), but namespace definitions (the xmlns:* attributes) are ignored.
If parsed as XML the attributes define the namespaces. You have to definitions:
- Alias `v`for `urn:schemas-microsoft-com:vml` - the Vector Markup Language
- Alias `o` for `urn:schemas-microsoft-com:office:office` - MS Office Open XML common attributes
XML namespaces allow to mix different XML formats and avoiding conflicts because of element names.
You file might be generated by MS Office (2003) or a user copied content from Office into it. If here are no elements/attributes starting with `v:` or `o:` in your document they don't do anything.
If the client knows a namespace/format it can interpret the elements. Not only a browser but RSS Readers, Calendars, ... If a client does not know a namespace but respects it, it at least knows to ignore the elements/attributes even if they have a name that might be valid in HTML.
Problem
I happened to find the sentence "xmlns:v=urn:schemas-microsoft-com" as title described Here is source roughly. ``` <!--[if gt IE 8]><!DOCTYPE html><!--<![endif]--> <!DOCTYPE html><!--<![endif]--> <html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office"><br> <head> <meta http-equiv="X-UA-Compatible" content="IE=Edge"> <meta name="viewport" content="user-scalable=0,target-densitydpi=device-dpi"> ... </head> <body> ... </body> </html> ``` As I know xmlns is schema, so to speak metadata. If some element is available in body section, the metadata of this element exist in "schemas.microsft.com" If I develop a html page using "microsoft" schema, all elements used in body section will be referernced by "microsoft" Or, If I use other schema, examply "google" (I don't know whether this really exist) all element goes same too. Here is my question First, If I use table tag that exist in "microsoft" and "google" schema together Will chrome browser interpret context differently? so comes differnt view? Second, If xmlns is omitted what kind of schema will be used default?