I have created Locally Presentable and Accessible Categories, with redirect LPAC, since we seem to refer to it a lot. I also added it as a reference to compact object, where it was surprisingly absent.

]]>pure morphism (much more to be said, and more references, but no time now)

]]>Started pure subobject. I wish someone would tell me the intuitive reason for their importance though!

]]>There’s a table on several nlab articles, for example at the bottom of accessible categories that relates “rich categories” with “rich preorders/posets”.

Most of it makes sense to me (Topos - Locale, Powerset - Presheaf), but I don’t understand the “accessible” column.
Specifically, the definition of accessible categories are categories as having directed colimits and a generating set of compact objects, is almost word for word the definition of *algebraic domain* used in for example Abramsky and Jung’s notes on domain theory, which is that it is a poset with directed suprema and a basis of compact objects.

It seems to me like these are the appropriate analogous concepts, for example the Ind-completion of a small category is the analogue of the Ideal completion of a poset.

So why is it that in the table posets are the analogue of accessible categories? I’m guessing there is a different analogy than I am thinking about?

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