Dependency vs Usage vs Association vs Connector

Gallery
Tutorial
TRAIL: Webel's ultimate guide to Systems Modeling Language (v1) with MagicDraw/Cameo
Section
08:01: The building Blocks of SysML
Topic level
BASIC
UML keywords
Dependency
Usage
Element
DirectedRelationship
Association
Connector
SysML keywords
Block
Slide kind
SysML Block Definition Diagram (BDD)
Rule-of-thumb: If it is likely that a connection will always be made (in an Internal Block Diagram (IBD) or internal structure compartment in a BDD) between two part properties corresponding to two typed Block instances, consider creating a named Association between the two parts - rather than (just) using a Usage or Dependency relationship - and type a Connector by it:
Webel Best Practice: If instances of Blocks “communicate” with each other use an Association between them.
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The anonymous Connector :UsbSource in the context block CarPlayingMusic has been typed by the named Association UsbSource.

BTW: The example here uses basic part-to-part connection (there are no ports involved yet).

Up next
Association vs Connector - detailed
Notes
[TOOL, WORKAROUND]{SUGGESTED} MagicDraw/Cameo: If you can't find Usage on a particular diagram just use a Dependency then the refactor context menu item.
[WARNING] The difference between Dependency and Usage in UML is notoriously vague.
[ASSERTION, TIP]{STRICT} When dealing with required Interfaces you must use Usage (not Dependency) and it has dedicated "socket" notation.
[TIP]{SUGGESTED} If instances of Blocks “communicate” with each other use an Association between them.
Snippets (quotes/extracts)
  [UML-2.5.1] A Dependency is a Relationship that signifies that a single model Element or a set of model Elements requires other model Elements for their specification or implementation.
  [UML-2.5.1] This means that the complete semantics of the client Element(s) are either semantically or structurally dependent on the definition of the supplier Element(s).
  [UML-2.5.1] A Usage is a Dependency in which the client Element requires the supplier Element (or set of Elements) for its full implementation or operation.
  [UML-2.5.1] A Connector specifies links that enables communication between two or more instances.
  [UML-2.5.1] In contrast to Associations, which specify links between any instance of the associated Classifiers, Connectors specify links between instances playing the connected parts only.
Visit also
Visit also (backlinks)
Related slides (includes other tutorials)
Related slides (backlinks, includes other tutorials)
Association and Property - some cases