UML Use Case Diagram. Design Elements

The vector stencils library "UML use case diagrams" contains 25 symbols for the ConceptDraw PRO diagramming and vector drawing software.
"Use case diagrams are usually referred to as behavior diagrams used to describe a set of actions (use cases) that some system or systems (subject) should or can perform in collaboration with one or more external users of the system (actors). Each use case should provide some observable and valuable result to the actors or other stakeholders of the system. ...
Use case diagrams are in fact twofold - they are both behavior diagrams, because they describe behavior of the system, and they are also structure diagrams - as a special case of class diagrams where classifiers are restricted to be either actors or use cases related to each other with associations. ...
Use case is usually shown as an ellipse containing the name of the use case. ...
Name of the use case could also be placed below the ellipse. ...
If a subject (or system boundary) is displayed, the use case ellipse is visually located inside the system boundary rectangle. Note, that this does not necessarily mean that the subject classifier owns the contained use cases, but merely that the use case applies to that classifier. ...
A list of use case properties - operations and attributes - could be shown in a compartment within the use case oval below the use case name. ...
Use case with extension points may be listed in a compartment of the use case with the heading extension points. ...
A use case can also be shown using the standard rectangle notation for classifiers with an ellipse icon in the upper right-hand corner of the rectangle and with optional separate list compartments for its features. ...
Subject (sometimes called a system boundary) is presented by a rectangle with subject's name, associated keywords and stereotypes in the upper left corner. Use cases applicable to the subject are located inside the rectangle and actors - outside of the system boundary. ...
Standard UML notation for actor is "stick man" icon with the name of the actor above or below of the icon. Actor names should follow the capitalization and punctuation guidelines for classes. The names of abstract actors should be shown in italics. ...
Custom icons that convey the kind of actor may also be used to denote an actor, such as using a separate icon(s) for non-human actors. ...
An actor may also be shown as a class rectangle with the standard keyword «actor», having usual notation for class compartments ...
An actor can only have binary associations to use cases, components, and classes. ...
An association between an actor and a use case indicates that the actor and the use case somehow interact or communicate with each other.
Only binary associations are allowed between actors and use cases.
An actor could be associated to one or several use cases. ...
A use case may have one or several associated actors." [uml-diagrams.org/ use-case-diagrams.html]
The example "Design elements - UML use case diagrams" is included in the Rapid UML solution from the Software Development area of ConceptDraw Solution Park.