In general, the SysML DirectedFeature approach is more powerful and the notation is cleaner than UML provided/required Interfaces. Prefer SysML DirectedFeatures unless you have a really good reason to use Interfaces!

Icon class
icon_class
far fa-sticky-note
icon_class_computed
far fa-sticky-note
Note kind
TIP
Policy level
STRONG
Specification keywords
SysML-1.6
UML keywords
provided Interface
required Interface
ball-and-socket
lollipop
SysMLv1.x keywords
DirectedFeature
FeatureDirectionKind::provided
FeatureDirectionKind::required
FeatureDirectionKind::providedrequired
Keywords
The older UML Interface and associated "ball and socket" or "lollipop and fork" notations are still supported in SysML v1.7, but the SysMLv1 InterfaceBlock with DirectedFeatures is more powerful and flexible and has better modelling support in Internal Block Diagrams.
SysML-1.7: 'A DirectedFeature indicates whether the feature is supported by the owning block (provided) for other connected blocks to use, or is to be supported by a connected block for the owning block to use (required), or both (providedRequired). A providedRequired feature specifies a symmetric dependency between two connected blocks whereby a block’s internal use of such a feature is delegated to the connected block with the corresponding feature and conversely that block’s internal use of ...'
SysML-1.7: 'The ~InterfaceBlock stereotype (shall be pronounced: "conjugated interface block") is a specialization of InterfaceBlock that has the same features as its original InterfaceBlock except that its DirectedFeatures and FlowProperties are reversed (conjugated'
SysML-1.7: 'A DirectedFeature has the same notation as other non-flow properties and behavioral features with a feature direction prefix (prov | reqd | provreqd), which corresponds to one the FeatureDirectionKind literals “provided,” “required,” and “providedrequired'
SysML-1.7: 'InterfaceBlock::isconjugated_not_used Any port typed by an InterfaceBlock shall have its isConjugated property set to false.'
SysML-1.7: 'Features that are not denoted as a DirectedFeature are implicitly provided features. As such they can be matched against a corresponding required feature.'
Relates to
[HISTORICAL] UML-STYLE: Hybrid SUV example: Ports with required/provided Interfaces (Block Definition Diagram)
[HISTORICAL] UML-STYLE: Hybrid SUV example: Ports with required/provided Interfaces (Internal Definition Diagram)
UML provided/required Interfaces vs SysML DirectedFeatures on Ports
Some valid FullPorts from the outside
REFERENCE CARD: Types of Block Properties and Block compartments
BehavioredClassifier and provided and required Interfaces
Required/Provided Interface notation: Ball-and-Socket "dependency wiring" [tool specific]
Conjugation in SysML-1.7 is Type-based: InterfaceBlock, ~InterfaceBlock, and DirectedFeature
Related notes
[POLICY]{STRONG} Avoid mixing flow properties on the Type of a Port with directed features (operations and values); One distinguishes between "ports with flows" and "contract ports".
[DISPLAY, STYLE, WARNING] Provided/required Interface "lollipop" and "socket" (a.k.a. ball-and-socket) notation can quickly lead to clutter in UML Composite Structure Diagrams and SysML Internal Block Diagrams. SysML provided/required DirectedFeature notation is cleaner.
[DISPLAY, STYLE] SysML directed features displayed on Port symbols are often far clearer than UML-style provided/required Interface "ball (lollipop) and socket" notation
[CAPABILITY, FEATURE, STYLE, TIP] TIP: MagicDraw/Cameo: Consider showing the Port name and type label inside the Port symbol! CAVEAT: This loses the direction indicators on Ports typed by Blocks with flow properties (but is fine if ItemFlows show the direction, or for "contract ports").
Related notes (backlinks)
Related snippets (extracts)
  [SysML-1.7] A DirectedFeature indicates whether the feature is supported by the owning block (provided) for other connected blocks to use, or is to be supported by a connected block for the owning block to use (required), or both (providedRequired).
  [SysML-1.6] [SysML1.6: PREFER SysML1.7] A DirectedFeature indicates whether the feature is supported by the owning block (provided), or is to be supported by other blocks for the owning block to use (required), or both ...
  [SysML-1.6] The ~InterfaceBlock stereotype (shall be pronounced: "conjugated interface block") is a specialization of InterfaceBlock that has the same features as its original InterfaceBlock except that its DirectedFeatures and FlowProperties are reversed (conjugated
  [SysML-1.7] InterfaceBlock::isconjugated_not_used Any port typed by an InterfaceBlock shall have its isConjugated property set to false.
  [SysML-1.7] A DirectedFeature has the same notation as other non-flow properties and behavioral features with a feature direction prefix (prov | reqd | provreqd), which corresponds to one the FeatureDirectionKind literals “provided,” “required,” and “providedrequired
  [SysML-1.7] A providedRequired feature specifies a symmetric dependency between two connected blocks whereby a block’s internal use of such a feature is delegated to the connected block with the corresponding feature and conversely that block’s internal use of ...
  [SysML-1.7] Features that are not denoted as a DirectedFeature are implicitly provided features. As such they can be matched against a corresponding required feature.
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