Where did the multigraded Segre product appear in the literature? Let $k$ be a field and $A\subset \mathbb{N}^d$ a vector configuration.  Let $R,S$ be commutative $k$-algebras, both graded by the affine semigroup $\mathbb{N}A$. Is the 'multidgraded Segre product' $R \otimes_{\mathbb{N} A} S := \bigoplus_{\mathbb{N} A} R_a \otimes_k S_a$ known in the literature?
 A: I believe that Segre product, at least in the particular case of grading over $\mathbb Z$ or $\mathbb N$ (I don't know what a vector configuration is), appears in literature in many places. One such place I am aware of is the book by Polishchuk and Positselski "Quadratic Algebras", AMS, 2005, where it is used to construct non-Koszul algebras with mutually inverse Hilbert series (p. 59 onwards). It is used also in the operadic environment (see, for example, a draft of the book by Loday and Vallette at http://math.unice.fr/~brunov/Operades.html ) what encompasses the above-mentioned algebra case and, probably, many other cases, including yours.
A: I found a precursor of the notion in the paper "On unmixedness theorem" by Chow (American Journal of Mathematics, Vol. 86, No. 4, Oct., 1964). He considers a Segre-type product of the form $\bigoplus_i R_{id} \otimes S_{ie}$ for given bi-degree $(d,e)$. This captures the idea of giving linear relations on the generating degrees (of the sub-algebra of the tensor product).
