Guest editorial for EMMSAD'2021 special section.

The program of this edition included 13 long and 1 short papers, divided into four sessions: enterprise modeling, handling models & modeling methods, threat & evidence modeling, and model-driven engineering & applications. The EMMSAD (Exploring Modeling Methods for Systems Analysis and Development) conference series organized 26 events from 1996 to 2021, associated with CAISE (Conference on Advanced Information Systems Engineering). These are organized into five tracks: (1) Foundations of Modeling & Method Engineering; (2) Enterprise, Business Process & Capability Modeling; (3) Information Systems & Requirements Modeling; (4) Domain-Specific & Ontology Modeling; and (5) Evaluation of Modeling Approaches. [Extracted from the article]