Creating items on a block definition diagram (SysML)
You can create items of the following types on a Block Definition Diagram: Activity, Actor, Block, Constraint Block, Flow Specification, Interface, Interface Block, Package, Quantity Kind, Signal, Unit, Use Case, Value Type, Attribute, Operation and Item Flow.
For information about creating Requirements on a Block Definition Diagram, see the SysML > Requirements section of this Help.
For information about creating OVM items on a Block Definition Diagram, see the following topics:
• Creating a variant.
• Creating a variation point.
• Creating an alternative choice.
To create an activity, actor, block, constraint block, flow specification, interface, interface block, package, quantity kind, signal, unit, use case, or value type:
1. In Modeler, open the Block Definition Diagram.
2. On the diagram's tab, click the 
Activity, 
Actor, 
Block, 
Constraint Block, 
Flow Specification, 
Interface, 
Interface Block, 
Package, 
Quantity Kind,
Signal, 
Unit, 
Use Case, or a 
Value Type button.
Activity, Actor, Block, Constraint Block, Flow Specification, Interface, Interface Block, Package, Quantity Kind, Signal, Unit, Use Case, or a Value Type button.3. On the Block Definition Diagram, click in free space.
4. Type the name of the item, and then press the Enter key.
To create an association block:
For more information about creating Association Blocks, click here 
Note that you can create an Association Block, one-to-one Association and Association Block Link in one operation through the Association Block button. How?
To create an item flow link:
1. On the diagram's tab, click the 
Item Flow Link button.
Item Flow Link button.2. Click the source Block or Interface Block, and then click the target Block or Interface Block.
3. From the Conveyed Classifier dialog, create or select the item that is conveyed by the Item Flow.
To create an item flow as a realization:
1. On the diagram's tab, click the Item Flow Realization button.
Item Flow Realization button.2. Click the Association that realizes the Item Flow.
3. To use an existing item as a conveyed classifier:
a. In the Options group, click the Existing Type option.
b. Select the item that you want to use as a conveyed classifier, and then click OK.
To create a new item to use as a type:
a. In the Options group, click the New Type option.
b. From the Type list, select the type of the item you want to create and use as a type.
c. In the Name box, type the name of the item that will be used as a type, and then click OK.
4. From the context menu, click the command for the receiving item of the Item Flow.
5. To select an Item Property for the Item Flow, right-click the Item Flow, point to Links, click Item Property, and then select the Block Property you want to use as the Item Property.
Alternatively,
1. In an appropriate pane, locate the Block, Interface Block, Signal, Value Type or Opaque Event that is to be conveyed by the Item Flow.
2. Drag the item from the appropriate pane to the Association on the diagram.
3. On the Select Item Flow dialog, select the New Type option.
4. In the Type list, select the type of the conveyed classifier.
5. In the Name box, type the name of the conveyed classifier, and then click OK.
6. From the context menu, click the command for the receiving item of the Item Flow.
7. To select an Item Property for the Item Flow, right-click the Item Flow, point to Links, click Item Property, and then select the Block Property you want to use as the Item Property.
For information about defining that an Item Flow is realized other items, click here