It declares that the string that follows... xmlns:xsi="something"... will be the URI of a namespace, and that all elements (and attributes) that are in the scope of this declaration and have the prefix "xsi:" will belong to the namespace.
It's the namespace URI (the "something" part up there) that identifies whether it's describing schemas or auto part requisitions. The prefix (the "xsi" part) has no meaning by itself. It is an arbitrary string that is used to relate the namespace to the elements and attributes that belong to the namespace.
That having been said, it's also traditional to use certain prefixes for certain namespaces. For example it's traditional to use the prefix "xsl:" for the XSL transformation namespace "http://www.w3.org/1999/XSL/Transform".
Joined: Nov 07, 2005
So, does that mean it is not mandatory to have this in the XML definition? Virtually every example I have seen has xmlns:xsi at the top. A lot of XML files do not reference this xsi prefix either.
It isn't mandatory for XML documents to use namespaces.
But somehow I doubt that is your question. If your XML document contains a namespace declaration, that really doesn't mean anything except to a program that knows what to do with that namespace. For example you can use the XSL transform namespace in an XML document if you like, but most programs won't do anything special with it unless they are using the document to do XSL transformations.
how does the xsi declaration actually work, is there a mapping to the url? like the way we use name space for a custom tag library and then it maps to tld file
the container knows where to search for the tld file (under WEB-INF folder)