type of TYPE="Text_t"

Imported from previous forum

Hi,
Just started working with FIXML, still can’t find anywhere what kind of data represented by type="Text_t like in the example below. How to iterpret this? Is is string? What are the rules for that kind of TYPE declaration, I see it’s differ form element name /even without _t/

xs:attribute use=“optional” type=“Text_t” name=“Txt”/
xs:attribute use=“optional” type=“EncodedTextLen_t” name=“EncTxtLen”/

Best
mario