The SysML Block is the basic element of SysML to move the UML Class – which is a software thing – to a higher level so that it can more naturally describe systems and other real-world items. A SysML Block defines a collection of features to describe a system.

The SysML Internal Block diagram captures the internal structure of a block in terms of properties and connectors between properties. A block can include properties to specify its values, parts, and references to other blocks. Ports are a special class of property used to specify allowable types of interactions between blocks.