No, there is more than one valid definition, the one you have used is the one used e.g. by the Unicode standard (but their definition is narrowed to Unicode, so anything not Unicode isn't plain text). But it doesn't matter which definition of "text" somebody uses, encoding is always a problem if not explicitly set like it is possible when using XML and HTML.
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No, there is more than one valid definition, the one you have used is the one used e.g. by the Unicode standard (but their definition is narrowed to Unicode, so anything not Unicode isn't plain text). But it doesn't matter which definition of "text" somebody uses, encoding is always a problem if not explicitly set like it is possible when using XML and HTML.
Love that typo :D