XML in a Nutshell, 3rd Edition

Character-Set Metadata

Some environments keep track of which encodings particular documents are written in. For instance, web servers that transmit XML documents precede them with an HTTP header that looks something like this:

HTTP/1.1 200 OK
Date: Sun, 28 Oct 2001 11:05:42 GMT
Server: Apache/1.3.19 (Unix) mod_jk mod_perl/1.25 mod_fastcgi/2.2.10 Connection: close
Transfer-Encoding: chunked
Content-Type: text/xml; charset=iso-8859-1

The Content-Type field of the HTTP header provides the MIME media type of the document. This may, as shown here, specify which character set the document is written in. An XML parser reading this document from a web server should use this information to determine the document’s character encoding.

Many web servers omit the charset parameter from the MIME media type. In this case, if the MIME media type is text/xml , then the document is assumed to be in the US-ASCII encoding. If the MIME media type is application/xml, then the parser attempts to guess the character set by reading the first few bytes of the document.

Tip

Since ASCII is almost never an appropriate character set for an XML document, application/xml is much preferred over text/xml. Unfortunately, most web servers including Apache 2.0.36 and earlier are configured to use text/xml by default. If you’re running such a version you should probably upgrade before serving XML files.^[1]

We’ve focused on MIME types in HTTP headers because that’s the most common place where character set metadata is ...