Xú Jiān 徐堅 (659–729), zì Yuángù 元固, native of Húzhōu 湖州 Wǔxìng 武興 — a scion of the great Chángchéng Xú 長城徐 lineage that produced (through his great-grandfather Xú Líng 徐陵) the celebrated LiángChénSuí zhèngyán compiler of the Yùtái xīnyǒng 玉臺新詠. CBDB id 30388 confirms the lifedates. He took jìnshì in 680 (or 681), passed the bóxué hóngcí 博學鴻詞 examination, and served in succession at the Jíxián shūyuàn 集賢書院, the Mìshū jiān 秘書監, and the Dōnggōng (Crown Prince’s household) as Chángcháng shìláng 太常侍郎. His long career under the Wǔ Zhōu and Xuánzōng made him one of the leading court compilers of the Jíxián diàn 集賢殿.
His principal works are the Chūxué jì 初學記 (KR3k0006), the 30-juan didactic lèishū commissioned by Xuánzōng in Kāiyuán 13 (725) — universally remembered as the most artistically successful of the early Táng lèishū — and contributions to the imperial Shìlèi 事類 (130 juan, lost) under Zhāng Yuè’s 張說 overall direction. He also wrote the Cháoyě shèngdiǎn 朝野盛典 (3 juan, lost) and was one of the principal compilers of the Liùdiǎn 六典 — the model later expanded into the Táng liùdiǎn 唐六典 (KR2g0007). He died in office at age 71. His biographies are in Jiù Táng shū 102 and Xīn Táng shū 199.