Qiyas extends a ruling established for an original case to a new case through a legally recognized effective feature shared by both. Its main components are the original case, new case, original ruling and operative cause.
Superficial similarity is not enough. Two objects may resemble one another in color or shape while lacking the relevant legal cause. An analogy also fails where it contradicts an authoritative text or modifies a text without adequate basis.
Structure: a ruling is established in the original case, a legally relevant factor explains its application, the factor occurs in the new case, and no effective impediment defeats the extension.
The operative cause may be supported by text, Sunnah or consensus, or inferred by juristic reasoning; these routes do not carry identical evidentiary standing.