SysML takes time and effort to learn. It is intended to be a conventional language for conducting [[model-based systems engineering]] but it has some important limitations that reduce its efficiency and limit its acceptance. This limited usage is, in itself, a limitation, as the SysML language can be considered a hermetic language that non-initiated find sometimes difficult to exploit.
SysML has been criticized for being incomplete although there is little to stop a practitioner from adding their own content. In SysML, there is no provision for several diagrams and graphically-oriented tools that are commonly used in system engineering. Some of these diagrams can be built, for example, by extending the intended use of block definition diagrams but the results are not always adequate and often not in concordance with the rules of the SysML language. Missing elements include [[functional block diagram]], [[N2 chart]] , [[House of Quality]], [[Ishikawa diagram]] (fishbone), parameter diagram and others. The language is continually improving and other diagram types are being considered for addition in future updates, should they be deemed sufficiently useful for inclusion.
The diagrams generated by SysML are complicated and some are difficult to understand by people that are unfamiliar with the language. Some elements are slightly counter-intuitive and this could lead to confusion and errors. This is occasionally aggravated by SysML users believing SysML should be a widespread convention. System-engineering diagrams are primarily intended for other members of an embedded team; people outside the team, more often than not, are not system engineers and are less likely to know SysML. This can be overcome by including explanatory notes and legends in SysML diagrams to ease their interpretation.
When drawn in a software tool, the diagrams that respect the rules of SysML often include redundant pieces of model information that can impair their interpretation.
