On Fri, 7 Dec 2018 17:19:35 -0500
Rik Kabel <context@rik.users.panix.com> wrote:

As a followup, here is a close-to-minimal example which demonstrates the 
failure when \placebtxrendering is omitted.

It is not a failure. The whole intent is to place an appropriate rendering that you can tailor to your specific needs. There is little sense in a cross-reference (link) or reference number if there is not sort of list.

Alan

That makes absolutely no sense. That means that an informal paper that puts all references in footnotes and has no bibliography and does not need cross-referencing or reference numbering cannot take advantage of a bibliographic database. And in fact, that is the case shown below. The footnotes appear only when the comment line is uncommented.

(I also tried \nocite[*] together with \placebtxrendering[method=none] and also with \placebtxrendering[criterium=none] for the rendering, but that does not help. It seems that the entries only display when something gets added to the rendering list.)

\startbuffer[quotesources]
@book{Schopenhauer1862v2,
  title       = {Parerga und Paralipomena},
  subtitle    = {Kleine Philosophische Schriften},
  publisher   = {A. W. Hahn},
  year        = {1862},
  volume      = {2},
  volumes     = {2},
  author      = {Arthur Schopenhauer},
  editor      = {Julius Frauenstädt},
  address     = {Berlin},
  language    = {german},
}
@book{SchopenhauerPayne2000,
  title       = {Parerga and Paralipomena},
  subtitle    = {Short Philosophical Essays},
  publisher   = {Oxford University Press Clarendon Press},
  address     = {New York and Oxford},
  year        = {2000},
  author      = {Arthur Schopenhauer},
  volumes     = {2},
  origyear    = {1974},
  origlanguage= {german},
  translator  = {Eric F. J. Payne},
}
\stopbuffer

\loadbtxdefinitionfile
  [apa]
\usebtxdefinitions
  [apa]
\usebtxdataset
  [quotesources.buffer]

\starttext

  As Artie said:\footnote{\placecitation[Schopenhauer1862v2]}

  Es wäre gut Bücher kaufen, wenn man die Zeit, sie zu
  lesen, mitkaufen könnte, aber man verweschelt meistens
  den Ankauf der Bücher mit dem Aneignen ihres Inhalts.

  Payne translates this as:\footnote{\cite[entry][SchopenhauerPayne2000]}

  Buying books would be a good thing if one could also
  buy the time to read them in: but as a rule the
  purchase of books is mistaken for the appropriation
  of their contents.

%  \placebtxrendering [method=dataset]
\stoptext

I understood §5.4 of the manual to mean that rendering definitions (created by \definebtxrendering and related setups) do not have an effect on \placecitation (and \cite[field][tag]) commands. Rereading it, I wonder if the meaning is supposed to be more than that, and to cover this situation?

Surely this can be changed!

--
Rik