This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Jacob ben Asher's major work, the Arba'ah Turim, organized the entire practical scope of Jewish law into four clearly bounded sections, covering daily and festival observance, dietary and ritual law, marriage and personal status, and civil and financial law, a documented structural division distinct from a single continuous legal treatise. Rather than presenting one settled ruling on each question, the Turim deliberately cited the conflicting positions of earlier authorities before Jacob ben Asher stated his own practical decision, a documented method that let a reader see the live disagreement a code more often hides.
That four-part architecture proved durable well beyond its own author's lifetime: two centuries later Joseph Karo built his own Shulchan Aruch directly on top of it, section for section, a documented case of one code adopting a predecessor's division as its own skeleton rather than devising a new organizing scheme from scratch. The Shulchan Aruch went on to become the standard code of practical Jewish law, carrying Jacob ben Asher's four-part structure forward as its own, still-standing architecture, even as its specific rulings diverged from the Turim's own.
That a fourteenth century compilation's organizing structure, rather than its individual legal conclusions, is what a later and more famous code chose to preserve marks the Arba'ah Turim's relationship to the Shulchan Aruch as a documented case where a code's lasting influence ran through its shape rather than through any single ruling it contained.