![]() ![]() This model level is used, for example, for the specification of test objects or objects for the simulation of a model. It is not relevant for answering the initial question, but for the sake of completeness a brief explanation of the third level: The object level represents objects (instance specifications) and object structures that describe a snapshot of a concrete system. For example, the syntax name:Definition is found in the CallBehaviorAction, which is an application respectively call of another activity. In the area of behavior, a distinction is also made between definition and application. It is a SysML connector and not an association. This time, the connection between the two ports is correct. The following figure shows the internal structure of the Assembly block from the above example in an internal block diagram. The specification therefore explicitly provides a delimiting explanation: “In contrast to Associations, which specify links between any instance of the associated classifier Connectors specify links between instances playing the connected parts only.” The relationship specified by the connector applies only in the context of the block to which the connected parts belong. And the connector as “A connector commits that between two or more instances.” That sounds initially very similar. The association is defined as “An association assigns a semantic relationship that can occur between typed instances. They look exactly like an association (solid line), but they are another model element and also mean something different. The parts or ports are connected in the internal block diagram with connectors. Likewise the ports, which are an application of interface definitions (InterfaceBlock). For example, the parts of a block are named this way. In most cases, the elements of the application level can be recognized by the syntax name:Definition. It is an application of block A.Īt the application level, defined elements are used. In the figure above, the left association defines the property a of type A by composition as part of the block Assembly. The association points to the definition of the part property (another block) and specifies the name and multiplicity at the end of the association. The association respectively the part property is modeled as a composition (black diamond). This does not yet define where and how the sensor is used.Īssociations are primarily used in system architecture modeling to define parts of a block (PartProperty). This also includes the interfaces of the sensor, which are described in SysML with ports. A block GPS sensor specifies characteristics of the sensor like a kind of data sheet in a catalog. The definition of the elements is independent of its application. These are, for example, blocks, associations, interface blocks. The block definition diagram, as the name implies, belongs to the definition level. The SysML language provides model elements and diagrams for each level. To understand why this is forbidden, I have to go further and explain the three levels of modeling of SysML.Ī SysML model distinguishes the three levels Definition, Application, and Objects. Therefore, I could create the following image only with the help of an image editor. The SysML forbids an association between ports and a good modeling tool should not allow that either. That is forbidden! But why? This blog post gives you the answer. It is tempting to connect the small port boxes in the block definition diagram with solid lines (= associations) to express that the corresponding building blocks communicate with each other. ![]()
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