The term "third image URI data" is not a common term in web development or computer science. It is possible that it may refer to a third backup or alternative URI (Uniform Resource Identifier) for an image, similar to the concept of a secondary image URI.
However, the use of a third image URI would be less common than the use of a secondary image URI, as having multiple backup image sources may not provide significant additional benefits in terms of ensuring the availability and reliability of image content.
XML supports data encoding and character sets for multilingual data representation by using the Unicode standard. The Unicode standard provides a standardized encoding for characters from most of the world's written languages, making it possible to represent and exchange multilingual data in a single, consistent format. To ensure that XML data is correctly encoded for a specific language or character set, the encoding declaration must be specified in the XML document. The encoding declaration is usually placed at the top of the document, within the XML declaration, and specifies the encoding used for the characters in the document.