SysML blocks are based on UML classes as extended by UML composite structures. Some capabilities available for UML classes, such as more specialized forms of associations, have been excluded from SysML blocks to simplify the language. Source OMG Systems Modeling Language (SysML) 1.6
Blocks may also specify operations or other features that describe the behavior of a system Source OMG Systems Modeling Language (SysML) 1.6
SysML also allows each usage to define context-specific values and constraints associated with the individual usage, such as 25 psi for the front tires and 30 psi for the rear tires. Source OMG Systems Modeling Language (SysML) 1.6
For example, a block that represents the definition of a wheel can be used in different ways. The front wheel and rear wheel can represent different usages of the same wheel definition. Source OMG Systems Modeling Language (SysML) 1.6
A part belonging to a block, for example, may be typed by another block. The part defines a local usage of its defining block within the specific context to which the part belongs. Source OMG Systems Modeling Language (SysML) 1.6
A property can represent a role or usage in the context of its enclosing block. A property has a type that supplies its definition. Source OMG Systems Modeling Language (SysML) 1.6
Various notations for properties are available to distinguish these specialized kinds of properties on an internal block diagram. Source OMG Systems Modeling Language (SysML) 1.6
Constraint Properties are a special class of property used to constrain other properties of blocks... Source OMG Systems Modeling Language (SysML) 1.6
Ports are a special class of property used to specify allowable types of interactions between blocks ... Source OMG Systems Modeling Language (SysML) 1.6
A block can include properties to specify its values, parts, and references to other blocks. Source OMG Systems Modeling Language (SysML) 1.6
