Draft:Neocategory
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Submission declined on 8 August 2026 by WeirdNAnnoyed (talk). This draft provides insufficient context for those unfamiliar with the subject. Please see the guide to writing better articles for how to improve your writing.
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Comment: This may be a notable topic, but the article provides almost no background for readers who aren't versed in the topic. Please provide a general introduction as a lead section. WeirdNAnnoyed (talk) 22:08, 8 August 2026 (UTC)
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In mathematics, a neocategory[2][3] (Ehresmann, who introduced this notion, called it a multiplicative graph [in French: graphe multiplicatif] [2]) is an algebraic structure in category theory. It is a generalization of an ordinary category in which the associative law of composition is not required, and is instead relaxed to a partial law of composition. While an ordinary category is a concept combining a directed graph and a monoidal structure, a neocategory is a partial magma-like structure. Namely, it is a structure in one‑to‑one correspondence with the nodes of a directed graph, and is equipped with partial law of composition that satisfies only left and right identities.[2] Cury is studying enriched neocategories under the term graphe multiplicatif enrichi.[4] As a more general notion, there is the compositional graph, and neocategories can be seen as strongly identitive compositional graphs.[3]
This notion first appears in Ehresmann's book Catégories et structures.[5] For the notion of a sketch which he himself introduced, Ehresmann needed to define a category-like structure that avoided redundant axioms as much as possible.[6] This structure is the neocategory, and this is a type of relaxed notion of category, such as a semicategory.[3]
Definition
| Total | Associative | Identity | Divisible | |
|---|---|---|---|---|
| Partial magma | Unneeded | Unneeded | Unneeded | Unneeded |
| Semigroupoid | Unneeded | Required | Unneeded | Unneeded |
| Small category | Unneeded | Required | Required | Unneeded |
| Groupoid | Unneeded | Required | Required | Required |
| Magma | Required | Unneeded | Unneeded | Unneeded |
| Quasigroup | Required | Unneeded | Unneeded | Required |
| Unital magma | Required | Unneeded | Required | Unneeded |
| Loop | Required | Unneeded | Required | Required |
| Semigroup | Required | Required | Unneeded | Unneeded |
| Associative quasigroup | Required | Required | Unneeded | Required |
| Monoid | Required | Required | Required | Unneeded |
| Group | Required | Required | Required | Required |
A neocategory is couple formed by a set denoted by , and a partial law of composition on satisfying the following axioms:[7][2]
- is a mapping from a subset of (denoted by and called the set of composable couples) into ; instead of , we write and we call the composite of .
- There exists a graph (i.e. and are retractions from onto a subset of , denoted by ), such that:
- (existence of units[8][9]): For each element of , the composites and are defined, and we have
- Here, is the right identity of and is called the source of , while is the left identity of and is called the target of ;
From the condition 2, the graph is uniquely defined.
Example
- An ordinary category is a neocategory in which all the couples where are composable (so that is the pullback of ), the law of composition being furthermore associative.[11][2]
See also
Notes
- ^ Cury 2004
- ^ a b c d e Bastiani & Ehresmann 1972, §1. Neocategories and neofunctors.
- ^ a b c Mateus, Sernadas & Sernadas 1999
- ^ Cury 1979
- ^ Ehresmann 1965, ch. I, Dèfinition 8.
- ^ Cury 2004, INTRODUCTION
- ^ Ehresmann 1965, ch. I, §.B) Graphes multiplicatifs et catègories. For the definition of "classe multiplicative", see ch. I, § A) Classes multiplicatives.
- ^ Ehresmann 1965, ch. I, Dèfinition 8. (G1)
- ^ a b Coppey 1980, 1. Graphes multiplicatifs, foncteurs, transformations naturelles.
- ^ Ehresmann 1965, ch. I, Dèfinition 8. (G2)
- ^ Ehresmann 1965, ch. I, Dèfinition 11.
References
- Bastiani, Andrée; Ehresmann, Charles (1972). "Categories of sketched structures" (PDF). Cahiers de Topologie et Géométrie Différentielle Catégoriques. 13 (2). ISSN 1245-530X.
- Coppey, L. (1980). "Quelques problèmes typiques concernant les graphes multiplicatifs" (PDF). Diagrammes (in French). 3 (2). ISSN 0224-3911.
- Mateus, Paulo; Sernadas, Amílcar; Sernadas, Cristina (1999). "Precategories for Combining Probabilistic Automata". Electronic Notes in Theoretical Computer Science. 29: 169–186. doi:10.1016/S1571-0661(05)80315-9.
- Ehresmann, Charles (1969). "Construction de structures libres". Category Theory, Homology Theory and their Applications II. Lecture Notes in Mathematics (in French). Vol. 92. pp. 74–104. doi:10.1007/BFb0080766. ISBN 978-3-540-04611-0.
- Ehresmann, Charles (1965). Catégories et structures (in French).
- Coppey, L.; Lair, C. (1984). "Leçons de théorie des esquisses" (PDF). Diagrammes (in French). 12 (4). ISSN 0224-3911.
- Cury, F. (1979). "Systèmes de générateurs et relations pour les catégories enrichies" (PDF). Diagrammes (in French). 1.
- Cury, F. (1978). Graphes multiplicatifs enrichis (Thesis) (in French).
- Cury, Florence (2004). "Graphes multiplicatis enrichis. Partie I" (PDF). Diagrammes (in French). 51: 1–46.
- Cury, Florence (2005). "Graphes multiplicatis enrichis. Partie II" (PDF). Diagrammes (in French). 53: 47–95.
- Cury, Florence (2006). "Graphes multiplicatis enrichis. Partie III" (PDF). Diagrammes (in French). 55: 96–120.
- Cury, Florence (2007). "Graphes multiplicatis enrichis. Partie IV" (PDF). Diagrammes (in French). 57: 121–183.
External link
- Tringali, Salvatore (2013). "Plots and Their Applications - Part I: Foundations". arXiv:1311.3524v1 [math.CT].
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