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--- bok:eng:mbse:sysml:req [2020/09/07 22:53]
anwlur created
+++ bok:eng:mbse:sysml:req [2020/11/14 06:49] (current)
anwlur added recommended language for requirements
@@ Line 1: / Line 1: @@
 ====== Modeling Requirements ======
+===== Categories =====
 A. Wymore postulates((Wymore, A. Wayne, A Mathematical Theory of Systems Engineering:  The Elements, John Wiley & Sons: New York, NY, 1967)) there are 6 categories of requirements:
@@ Line 11: / Line 13: @@
 Each system must fulfill these requirements.
+===== Language =====
+Taken from NASA’s ISS Crew Transportation and Services Requirement Document((http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150010757.pdf))
+In the context of a contract:
+  * **"Shall"** is used for binding requirements that must be verified and have an accompanying method of verification;
+  * **"Will"** is used as a statement of fact, declaration of purpose, or expected occurrence;
+  * **"Should"** is used to denote an attribute or best practice which must be addressed by the system design.
+When used within the context of a reference document under an agreement, the verbs shall, will, and should are only intended as informational and are not binding.
+In some cases, the values of quantities included in this document have not been confirmed and are designated as:
+  * **"To Be Confirmed" (TBC)** – still under evaluation,
+  * **"To Be Determined" (TBD)** or **"To Be Supplied" (TBS)** – known, but not yet available,
+  * **"To Be Resolved" (TBR)** is used when there is a disagreement on the requirement between technical teams.
+When a change in a noted characteristic is deemed appropriate, notification of the change shall be sent to the appropriate review and change control authority.

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