The input to the Similar Text request has several forms, and is specified by the mode attribute.
<similardocs mode="mode"<input>input</input>The mode value can be one of four values:
text—Raw, unformatted text of any kind
xhtml—Structured text in the format described in the Structured Content Queries chapter.
url—URL of a previously viewed index item
hdoc—Document identifier of an indexed item
