Works on ʿilal investigate subtle defects and disagreements in chains or wordings. The point is to compare routes and transmitters rather than to reproduce a single isnād without analysis.
Works on aṭrāf use a recognizable opening or phrase from a hadith to direct readers to its chains or sources. This helps researchers trace variants once they recognize the report.
Other compilations gather the traditions of one source, cross-reference several collections, or concentrate on conflicting chains of one report.
Organization follows research purpose. The reader must understand the compiler's selection criteria and the limits of the work before drawing conclusions.