This statement cannot be relied upon, as Simeon Kayyara in fact lived in the century following Yehudai Gaon; and Halevy is of the opinion that the names were inadvertently switched, though this reading creates as many problems as it solves.
It would also seem from the statements of these authorities that Simeon Kayyara's chief sources were the She'iltot of Ahai of Shabha and the Halachot Pesukot of Yehudai ben Nahman .
[5] It gives the entire halakhic and practical material of the Talmud in a codified form, and seems to represent the first attempt to treat it according to its contents rather than according to the arrangement of its treatises.
At the time of that edition it was more difficult to trace material borrowed from Yehudai Gaon's Halakhot Pesukot, since the original form of that work had been lost.
The original or Babylonian redaction exists in printed form in the editions of Venice (1548), Amsterdam (1762), Vienna (1810), etc., and finally in that of Warsaw (1874, with an index of passages and notes by S. A. Traub).
This redaction was used by the Babylonian geonim and by the German and northern French scholars; for the citations of the latter from the Halakhot Gedolot, which work they ascribe to Yehudai Gaon, refer to this recension.
The second or so-called Spanish redaction (Mahadurat Aspamia) exists in a manuscript in the Vatican library, and has been edited by A. Hildesheimer in the collection of the Mekitze Nirdamim (Berlin, 1888–92).
The material of this recension is much richer and more comprehensive, since it contains many passages from the Talmud, mnemonic introductory words ("simanim"), the order of the weekly lessons, and, most important of all, legal decisions of the Geonim, usually indicated by the term "shedar" (="he sent"), which are lacking in the earlier redaction.
A. Epstein has concluded, accordingly, that this redaction was made, or rather finished, about the year 900, in some place where the Jews were in close literary correspondence with the Babylonian seminaries.