Abstract. If the standard concepts of partial-order relation and subset are fuzzified, taking valuation in a unital commutative quantale Q, corresponding concepts of joins and join-preserving mappings can be introduced. We present constructions of limits, colimits and Hom-objects in categories Q-Sup of Q-valued fuzzy joinsemilattices, showing the analogy to the ordinary category Sup of join-semilattices.
IntroductionIn the standard concept of a fuzzy set [11], the relation "x is an element of X" is fuzzified, and replaced by a mapping X → [0, 1] assigning to each element of X its "membership degree". As further generalization, the membership degree can be evaluated in structures more general than the real unit interval, typically frames, residuated lattices, or quantales.In our paper, the concept of a set remains unchanged, and it will be the partial order relation and the notion of a subset that will be replaced by suitable mappings to a quantale. Instead of considering on X a partial order relation ≤, we employ a unital quantale Q and mappings M : X → Q and e : X × X → Q, which quantify the "degree of truth" of membership in a subset and of being less or equal.Sets equipped with quantale-valued binary mappings were initially investigated in the so-called quantitative domain theory [4]. A number of papers on the topic of sets with fuzzy order relations valuated in a complete lattice with additional structure have been published in recent years. Among many others, articles [9,10,12] may be used as a reference. There are various structures used for fuzzy valuation in the literature, e.g., frames [3] and complete residuated lattices [12], both being just special cases of quantales. Also terminology has not settled yet, and differs among authors. As the multiplicative unit of a quantale need not be its top element, even truth can have more degrees in Q. This is different from valuation using frames or residuated lattices where the unit is the top element as well.The basic properties of the category of complete join-semilattices as well as the fundamental constructions in this category such as limits and colimits have MSC (2010): primary 08A72, 06F99; secondary 18B35.