When interpreters reflect on their own use of signs they require an appropriate technical language in which to pursue these reflections. For this they need signs that refer to sign relations, signs that refer to elements and components of sign relations, and signs that refer to properties and classes of sign relations. The orders of signs that develop as reflection evolves can be placed under the description of higher order signs and the extended sign relations that involve them can be referred to as higher order sign relations.
I’ve been working apace to format my old dissertation proposal on Inquiry Driven Systems for the web, but I was reminded of this part when the subject of “signs about signs” came up recently on the Peirce List.