2022-02 - SysML v2 Pilot Implementation

This is an incremental update to the 2022-01 release. It corresponds to Eclipse plugin version 0.21.0.

Language Features

1. Feature chain expressions. Expressions of the form expr.x.y.z that were previously parsed as path step expressions are now parsed in a slightly simpler and more semantically correct way as feature chain expressions.

Model Library

Kernel Library

1. Occurrences
   • Added modeling for spatial aspects of Occurrence and for constructive relations on occurrences of union, intersection and difference.
   • Added associations to represent spatial relationships SpaceSliceOf, SpaceShotOf and OutsideOf, and the spacetime relationship WithOut.
2. Objects
   • Added specializations of Object for Body, Surface, Curve and Point, of inner space dimension 3, 2, 1 and 0, respectively.
   • Added StructuredSpaceObject to represent an Object that is broken up into cells of the same or lower inner space dimension (faces, edges and vertices).
3. SpatialFrame (new). Models spatial frames of reference for quantifying the position vector of a point in a three-dimensional space.
4. VectorValues (new). Provides a basic model of abstract vectors as well as concrete vectors whose components are numerical values.
5. VectorFunctions (new). Defines abstract functions on VectorValue corresponding to the algebraic operations provided by a vector space with inner product. It also includes concrete implementations of these functions specifically for CartesianVectorValue.
6. TrigFunctions (new). Defines basic trigonometric functions on real numbers and provides a constant feature for pi.

Systems Library

1. Items. Added the following features:
   • shape - The shape of an item is its spatial boundary.
   • envelopingShapes - Other shapes that spatially envelop an item.
   • isSolid - An Item is solid if it is three-dimensional and has a non-empty shape (boundary).

Quantities and Units Domain Library

1. Quantities. VectorQuantityValue is now a kind of NumericalVectorValue (from VectorValues).
2. VectorCalculations. Revised to provide calculation definitions for VectorQuantityValue that specialize the corresponding functions from VectorFunctions.

Geometry Domain Library

1. SpatialItems (new). Models physical items that have a spatial extent and act as a spatial frame of reference for obtaining position and displacement vectors of points within them.
2. ShapeItems (new). Provides a model of items that represent basic geometric shapes.

Backward Incompatibilities

1. Select and collect expressions. The new shorthand notation for expr->select{...} is expr.?{...}. The shorthand notation previously used for select, expr.{...}, is now a shorthand for expr->collect{...}.
2. Suboccurrences. The feature suboccurrences of Occurrence has been renamed to spaceEnclosedOccurrences.
3. Sum and product functions. The sum and product functions have been moved into NumericalFunctions and removed from DataFunctions and ScalarFunctions.
4. Mathemetical function names. Non-operator mathematical functions from the various Kernel mathematical function packages have been updated to have a more consistent convention of names starting with a lower case letter.
5. BasicGeometry. The BasicGeometry model previously in the Geometry Domain Library has been deleted.

Jupyter

None.

Visualization

1. PlantUML
   None.
   
2. Tom Sawyer
   None.

Technical Updates

None.

Bug Fixes

Implementation

1. Assumed and required constraints. Fixed the implmentation of getAssumedConstraintImpl and getRequiredConstraintImpl in RequirementUsageImpl.
2. Owned connections. Fixed the implementation of getOwnedConnection in DefinitionImpl.
3. Validation. Corrected the multiplicity lower bound validation for end features.

Library

1. Portions. Constrained the portions of an occurrence to have the same life as the occurrences they are portions of.
2. PortionOf. Corrected the order of the end features of the Occurrences::PortionOf association.
3. SnapshotOf. Corrected the multiplicity of SnapshotOf::snapshottedOccurrence.
4. VectorQuantityValue. Updated Collections::Array to allow dimensionless arrays of a single value. This then allows a VectorQuantityValue to be dimensionless (order 0), correcting the former inconsistency of ScalarQuantityValue (with order 0) being a specialization of VectorQuantityValue (previously required to have order 1).

2022-01 - SysML v2 Pilot Implementation

This is an incremental update to the 2021-12 release. It corresponds to Eclipse plugin version 0.20.0.

Language Features

KerML

1. Return parameters. It is now possible to mark a parameter declared in a function body as the return parameter in the KerML textual notation (as was already possible in SysML).

SysML

1. Accept actions. The notation for accept actions (used either within an action model or in a transition) has been updated to allow the payload parameter to be declared with a feature value or incoming flow. In this case, an accepted transfer must have a payload identical to the bound or flowed value.

   • acceptpayloadName:PayloadType=valueExpression;
   • acceptpayloadName:PayloadTypeflow fromsource;

   Note. The syntactic form acceptPayloadType;, without a colon in the payload declaration, is still allowed and still represents a declaration of the payload type, not its name. A binding or flow cannot be included in a declaration of this form.

2. Change triggers. A change trigger of the form whenchangeCondition can now be used in place of a feature value in a payload declaration. The changeCondition must be a Boolean-valued expression, and the trigger fires when the expression result changes from false to true (or if the result is true when first evaluated).

   • acceptpayloadName:PayloadTypewhenchangeCondition;

   Note. The explicit declaration of the payload parameter is optional, allowing the simple form accept whenchangeCondition;. The form acceptpayloadNamewhenchangeCondition; is also allowed, but this represents a declaration of the payload name, not its type.

3. Time triggers. A time trigger of the form attimeExpression or afterdurationExpression can now be used in place of a feature value in a payload declaration. The timeExpression must result in a TimeInstantValue, and the trigger fires at that time (relative to the default clock). The durationExpression must result in a DurationValue, and the trigger fires after the elapse of that duration (on the default clock).

   • acceptpayloadName:PayloadTypeattimeExpression;
   • acceptpayloadName:PayloadTypeafterdurationExpression;

   Note. Simplified payload declarations are allowable for time triggers, similarly to change triggers.

Model Library

1. FeatureReferencePerformances. The Kernel Library package FeatureAccessPerformanceshas been renamed to FeatureReferencingPerformances, and the following behaviors have been added to it:
   • FeatureMonitorPerformance
   • EvaluationResultMonitorPerformance
   • BooleanEvaluationResultMonitorPerformance
   • BooleanEvaluationResultToMonitorPerformance
2. Clocks and Triggers. The following packages have been added to the Kernel Library:
   • Observation – models monitoring for change and notifying registered observers.
   • Clocks – models clocks that provide a current time reference, with functions for getting the time and duration of an Occurrence relative to a clock.
   • Triggers – provides convenience functions for creating monitored change signals for change triggers, absolute time triggers and relative time triggers.
3. Time. A specialization of the Kernel Clock model has been added to the Quantities and Units Library Time package, using time instant and duration quantity values.
4. SI. ScalarQuantityValue in the Quantities and Units Library Quantities package is now a specialization of NumericalValue instead of ScalarValue.

Backward Incompatibilities

1. Keywords.
   • KerML: Added: return
   • SysML: Added: when at after
2. FeatureReferencePerformances. The Kernel Library package FeatureAccessPerformanceshas been renamed to FeatureReferencingPerformances.
3. SI. The Quantities and Units Library package SI no longer imports QuantityCalculations. These means that the SI package no longer re-exports the the calculation definitions from QuantityCalculations or various other members re-exported from QuantityCalculations (such as from ScalarValues and Quantities).
4. Time. The order of the public owned features of the Iso8601DateTime and Iso8601DateTimeStructure calculation definitions in the Quantities and Units Library has been changed so the non-redefining parameters come first (allowing a more natural use of positional argument notation when invoking these calculations).
5. USCustomaryUnits. Units other than actual US customary units have been removed from this package.

Jupyter

None.

Visualization

1. PlantUML
   • Imports (both element and package, recursive or not) are now rendered using the dashed arrow notation. A new option, SHOWIMPORTED, has been added which shows imported elements as well as the traversed elements.
     
2. Tom Sawyer
   None.

Technical Updates

None.

Bug Fixes

1. KerML relationship notation. Fixed the KerML grammar so that

• A Relationship that is an owned related element of another relationship can have unowned related Eeements.
• A Relationship can have only owned related elements.
• All owned related elements of a relationship are added to its targets.

2021-12 - SysML v2 Pilot Implementation

This is an incremental update to the 2021-11 release. It corresponds to Eclipse plugin version 0.19.0.

Language Features

1. If actions. An if action evaluates a Boolean-valued condition. If the result is true, it performs a nested then action, otherwise it performs a nested else action.
   • An if action has the form
     actionifNameifconditionactionthenActionName{ ... }else actionelseActionName{ ... }
   • The action declaration part may be omitted for the entire if action, the then action and/or the else action:
     ifcondition{ ... }else{ ... }
     The curly braces are required, even if the body of the then action or else action is empty, unless the else action is itself an if action, in which case a simplified notation can be used:
     ifcondition{ ... }else if{ ... }else{ ... }
     This is equivalent to
     ifcondition{ ... }else{if{ ... }else{ ... } }
   • The else action is optional. If it is omitted, then no action is performed if the condition is false.
2. While-loop actions. A while-loop action repeatedly performs a nested body action as long as a Boolean-valued while condition is true and an until condition is false. The while condition is evaluated before each iteration, and the until condition is evaluated after the iteration.
   • A while loop action has the form
     actionwhileLoopNamewhilewhileConditionactionbodyName{ ... }until untilCondition;
   • The action declaration part may be omitted for the entire while-loop action and/or the body action:
     whilewhileCondition{ ... }until untilCondition;
     The curly braces are required, even if the body is empty.
   • The until condition is optional. If it is omitted, then the default is untilfalse (that is, no effect).
     whilewhileCondition{ ... }
   • The while condition may be replaced with the keyword loop, which is equivalent to whiletrue.
     loop{ ... }until untilCondition;
     If the until condition is also omitted, then the action specifies a non-terminating loop.
     loop{ ... }
3. For-loop actions. A for-loop action iterates over the values resulting from the evaluation of a sequence expression, assigning each in turn to a for variable feature and performing a nested body action for the assigned value.
   • A for-loop action has the form
     actionforLoopNameforforVariableDeclinsequenceExpractionbodyActionName{ ... }
   • The action declaration part may be omitted for the entire for-loop action and/or the body action:
     forloopVariableDeclinsequenceExpr{ ... }
4. Path expressions. Previously, a path expression of the form expr.a.b.c was parsed as a tree of path step expressions. That is, it was parsed like (expr.a).b).c). Such expressions are now parsed so that a trailing path of two or more features parses as a feature chain. That is, expr.a.b.c parses as a single expression that applies the feature chain (e.g., a.b.c) to the result of the expression expr.

Model Library

1. Occurrences. The HappensDuring and HappensBefore associations in the Occurrences Kernel Library model have been updated with cross-relation and transitivity constraints and the semantic constraints on the HappensJustBefore association have been simplified.
2. Actions. Added the action definitions IfThenAction, IfThenElseAction, LoopAction, WhileLoopAction and ForLoopAction, along with corresponding base usages, to the Actions Systems Library model.
3. SI. The longName feature binding has been removed from unit declarations. The declarations have been revised so that the declared unit name is its "long name" and its human ID is its abbreviation. Due to the name resolution rules for human IDs, this should have no effect on existing user models.
4. USCustomaryUnits. A large number of additional units have been added to the USCustomaryUnits model from the Quantities and Units Domain Library, based on the NIST SP811 standard. (Note, however, that a further update to this package is expected in the next release.) All unit declarations in the package now also use the same naming convention described above for the SI package.

Backward Incompatibilities

1. Keywords. SysML: Added: loop until while.
2. Implicit typing. The following improvements have been made to the implicit typing of certain expressions, which may result in new type warnings in some places.
   • The result of a path step expression (e.g., expr.a.b.c) is typed like the result of the feature or feature chain being accessed (e.g., a.b.c).
   • The result of a path select expression (i.e., expr.{ ... }) is typed like the result of its first argument (expr), which is the expression that evaluates to the collection being selected from.
   • The result of an invocation expression used as a constructor for a non-function type (e.g., ItemType( ... )) is typed by the type being constructed (e.g., ItemType).
3. Measurement unit "long names". The longName feature has been removed from the TensorMeasurementReference definition in the UnitsAndScale model from the Quantities and Units Library. If longName was being bound in a unit declaration, the value should instead be used as the name of the unit, with the short name or abbreviation used as the human ID.

Jupyter

None.

Visualization

1. PlantUML
   None.
   
2. Tom Sawyer
   None.

Technical Updates

1. Content assist. The Xtext generation workflows have been updated to remove the generation of content assist code, including the content-assist-specific parser. This was necessary due to a problem with the generation of the content-assist parser (see the in PR #313), and it resolves the known issue of the editors hanging when content assist is triggered (see issue #220). A custom implementation of content assist may be considered in the future, as time and resources permit.

Bug Fixes

1. Operands. Fixed the duplicated serialization into XMI of the operands of an OperatorExpression. This also eliminated the duplicate validation checks and error messages on operands.

2021-11 - SysML v2 Pilot Implementation

This is an incremental update to the 2021-10 release. It corresponds to Eclipse plugin version 0.18.0.

Language features

1. Assignment actions. An assignment action is used to change the value of a feature at the time of performance of the action.

   • Assignment to feature in scope. Assigns the result of valueExpression to the feature with a featureName in the current scope.

     assignfeatureName:=valueExpression;

     Example: assigncurrentStatus := StatusEnum::Nominal;

   • Assignment to feature of a target occurrence. Assigns the result of a valueExpression to the feature with name featureName of the occurrence that is the result of a targetExpression.

     assigntargetExpression.featureName:=valueExpression;

     Example: assigntrailer.trailerFrame.coupler := vehicle.hitch;

     Note: In this case the targetExpression is the path step expression trailer.trailerFrame, and the valueExpression is also a path step expression, vehicle.hitch. The featureName is coupler.

2. Initial values. An initial value is specified when declaring a feature similarly to a bound value, but using the symbol := rather than =. The feature is set to the specified initial value at the start of the lifetime of its containing occurrence, and, unlike if a bound value was specified, the initial value can be subsequently changed using an assignment action.

   attributecount : Integer := 0;

   It is also possible to mark an initial value as a default, in which case it may be overridden in a redefinition of the feature.

   itemsensordefault:= primarySensor;

3. Invocation using feature chains. Feature chains can now be used as the target of invocation expressions.

   directory.addressOf(userName)

4. Implicit typing. If a feature is declared without an explicit feature typing, but with a feature value, then the feature is implicitly typed by the result type of the feature value expression.

   attributecolor = ColorEnum::red; // color implicity has type ColorEnum.

   Note that this also works if the feature value is initial and/or default.

Model Library

1. AssignmentAction. Added the action definition AssignmentAction and the action usage assignmentActions to the SysML Actions model library.

Backward incompatibilities

1. Keywords. SysML: Added: assign.

2. Risk metadata. The enumerated values for the LevelEnum and RiskLevelEnum in the RiskMetadata model have been renamed from L, M, H to low, medium, high.

3. Trade studies. The calculation definition ObjectiveFunction in the TradeStudies model has been renamed EvaluationFunction and the corresponding calculation feature TradeStudy::objectiveFunction has been renamed evaluationFunction.

4. Enumerations. Previously, if a feature was typed by an enumeration definition, then the name of an enumerated value from the definition could be used as a feature value without qualification. However, it is now necessary to qualify the name, unless it has otherwise been imported into the local namespace.

   attributecolor : ColorEnum = ColorEnum::red; // Qualification is necessary.

Jupyter

None.

Visualization

1. PlantUML
   • Added new view for cases, including analysis cases, verification cases and use cases.
   • Added special rendering for actors and stakeholders in the tree view.
   • Added compartment rendering for connections.
   • Corrected the rendering of flow connections in the interconnection view.
     
2. Tom Sawyer
   • Implemented visualization of "proxy" connections and connection points.
   • Implemented a view that combines aspects of a tree and a nesting view, through actions that expand single nodes as nesting or as a tree.

Technical Updates

1. Eclipse. Updated the development baseline to Eclipse version 2021-09.

Bug Fixes

1. Variations. Declaring a case (of any kind) to be a variation no longer results in a spurious "A variation must only have variant owned members." error.
2. Protected visibility. Fixed the resolution of the name of an inherited member with protected visibility when referenced in a nested scope. Also updated handling of protected visibility to conform to the current specification that resolution of qualified names requires that all segments but the first have public visibility.
3. Feature value scoping. Names in feature value expressions are now resolved starting with the scope of the owning namespace of the corresponding feature declaration, not in the scope of the feature itself, eliminating anomalous resolution to members of the feature. (Note, however, that this causes the backwards incompatibility for enumerations described above.)
4. Metadata visualization. For PlantUML, fixed the visualization of feature chains used to specify a metadata feature.
5. Requirement constraints. For PlantUML, fixed the visualization of require and assume constraints in the constraint compartment of a requirement definition or usage.

2021-10 - SysML v2 Pilot Implementation

This is an incremental update to the 2021-09 release. It corresponds to Eclipse plugin version 0.17.0.

Language features

1. Derived and read-only features. In both KerML and SyML, the keywords derived and readonly can be used when declaring a feature/usage with metaproperty isDerived = true or isReadOnly = true, respectively.
2. Package body elements. Removed the restriction in the SysML syntax on declaring flow connections directly at package level (i.e., not as the feature of a definition or usage).

Model Library

1. HappensJustBefore. Added the association HappensJustBefore to the Kernel Library Occurrences model, to represent the relationship of one occurrence happening just before another, that is, when no occurrence exists that is after the first occurrence and before the second occurrence. (This is the "meet" relation in the Allen time interval formalism.)

Backward incompatibilities

1. Keywords.
   • KerML: Added: derived readonly. Removed: id stream.
   • SysML: Added: binding derived readonly. Removed: id stream.
2. Human IDs. In both KerML and SysML, the syntax for declaring a human ID has changed from idname to <name>.
3. Flow connections. In both KerML and SysML, the keyword for flow connections has changed from stream to flow. The keyword for succession flow connections has changed from flow to succession flow.
4. Binding connections. The SysML syntax for named binding connections has changed from bindnameassource=target; to bindingnamebindsource=target; The syntax for unnamed binding connections remains unchanged: bindsource=target;.
5. Successions. The SysML syntax for unnamed successions has changed from successionsourcethentarget; to firstsourcethentarget;. The syntax for named successions remains unchanged: successionnamefirstsourcethentarget;

Jupyter

None.

Visualization

1. Tom Sawyer
   • Revised visualization of human IDs.
     
2. PlantUML
   • Revised visualization of human IDs.

Bug Fixes

1. Include use case usages. Fixed the implementation of effective names of include use case usages.

2021-09 - SysML v2 Pilot Implementation

This is a maintenance update to the 2021-08 release. It corresponds to Eclipse plugin version 0.16.0.

Language features

No updates.

Model Library

1. Connections. Added FlowConnection/flowConnections and SuccessionFlowConnection/successionFlowConnections base types to the Connections library model.
2. Kernel. Updated some Kernel Library package documentation consistent with KerML specification document.

Backward incompatibilities

1. Flow connections. Due to the new library model for message, stream and flow connections, it is no longer allowable to use them as the target of perform actions. Use event or ref subsets instead.

Jupyter

None.

Visualization

1. Tom Sawyer
   None.
   
2. PlantUML
   • Visualization of parameters and inherited members.
   • Visualization of subsetting in textual feature representation.
   • New style options:
     • SHOWINHERITED – Show inherited members
     • SHOWLIB – Show elements of the standard libraries
     • COMPMOST – Show as many memberships in a compartment as possible

Bug Fixes

1. Allocation definitions. Ensured that all allocation definitions directly or indirectly specialize the base Allocation type, no matter how many ends they have.
2. Association and connection ends. Ensured that the ends of non-binary associations and connection definitions directly or indirectly subset Link::participant.
3. Connector ends. Limited the special scoping of the targets of connector end subsettings to the first subsetting (i.e., the one giving the related element for the end).

2021-08.1 - SysML v2 Pilot Implementation

This release is the same as the 2021-08 release, except that it fixes a bug in the %publish Jupyter magic command. It corresponds to Eclipse plugin version 0.15.2.

The release notes for 2021-08 are repeated below for convenience, with the additional bug fix shown in bold.

Language features

No updates.

Model Library

Improved documentation comments in Metadata and Analysis library models.

Backward incompatibilities

None.

Jupyter

1. Show JSON. Added a --style json option to the %show command to show model elements in a JSON representation.
2. Export JSON. Added an %export command to export model elements to a file in a JSON representation.
3. Installer. Updated the Jupyter installer to pull from conda-forge and npm.

Visualization

1. Tom Sawyer
   • Visualization of binding connectors nested in action parameters.
   • Visualization of item flows nested in source actions.
     
2. PlantUML
   • Visualization of simple sequence diagrams.

Bug Fixes

1. KerML Grammar. For FeatureTyping, corrected the generalization keyword to specialization.
2. SysML Grammar
   • ActionBodyItem - Added alias members.
   • Parameter - Added UseCaseUsage parameters.
   • StateBodyItem - Added alias members.
3. Link. Fixed the spurious implicit specialization by Link of BinaryLink.
4. XMI. Fixed a possible IndexOutOfBoundsException when save SysML modes to XMI.
5. Event Occurrence Usages. - Made instances of EventOccurrenceUsage (and all subclasses) to be always referential.
6. Feature Chains. - Corrected resolution of feature chains used as connector ends.
7. Satisfying Features. - Corrected the implementation of the derivation of SatisfyRequirementUsage::satisfyingFeature.
8. Tom Sawyer. Fixed membership of elements in the outline view.
9. PlantUML. Fixed rendering of unnamed actions and states and of satisfying feature links.
10. Publishing. Restored the writing of derived property values when publishing a model from Jupyter.

2021-08 - SysML v2 Pilot Implementation

This is a maintenance update to the 2021-06 release (there was no 2021-07 release). It corresponds to Eclipse plugin version 0.15.1.

Language features

No updates.

Model Library

Improved documentation comments in Metadata and Analysis library models.

Backward incompatibilities

None.

Jupyter

1. Show JSON. Added a --style json option to the %show command to show model elements in a JSON representation.
2. Export JSON. Added an %export command to export model elements to a file in a JSON representation.
3. Installer. Updated the Jupyter installer to pull from conda-forge and npm.

Visualization

1. Tom Sawyer
   • Visualization of binding connectors nested in action parameters.
   • Visualization of item flows nested in source actions.
     
2. PlantUML
   • Visualization of simple sequence diagrams.

Bug Fixes

1. KerML Grammar. For FeatureTyping, corrected the generalization keyword to specialization.
2. SysML Grammar
   • ActionBodyItem - Added alias members.
   • Parameter - Added UseCaseUsage parameters.
   • StateBodyItem - Added alias members.
3. Link. Fixed the spurious implicit specialization by Link of BinaryLink.
4. XMI. Fixed a possible IndexOutOfBoundsException when save SysML modes to XMI.
5. Event Occurrence Usages. - Made instances of EventOccurrenceUsage (and all subclasses) to be always referential.
6. Feature Chains. - Corrected resolution of feature chains used as connector ends.
7. Satisfying Features. - Corrected the implementation of the derivation of SatisfyRequirementUsage::satisfyingFeature.
8. Tom Sawyer. Fixed membership of elements in the outline view.
9. PlantUML. Fixed rendering of unnamed actions and states and of satisfying feature links.

2021-06.1 - SysML v2 Pilot Implementation

This is an incremental update to the 2021-05 release. It corresponds to Eclipse plugin version 0.14.1.

This release is the same as the 2021-06 release, except that it fixes a missing update to the textual notation for transitions, to allow dot notation to be used for the transition source. The release notes for 2021-06 are repeated below for convenience.

Language features

KerML and SySML

1. Import.
   a. Member Import. Single member import is no longer equivalent to aliasing. The notation importnamespaceQualifiedName::elementName; now imports the membership in the imported namespace given by namespaceQualifiedName whose member name is given by elementName. This works properly even if given elementName is an alias name. If namespaceQualifiedName is not given, then elementName is resolved in the containing scope of the import.
   b. Recursive Import. As previously, a recursive import of the form importnamespaceQualifiedName::**; includes the members of the namespace given by namespaceQualifiedName as well as members recursively imported from namespaces contained in the given namespace. There is now also a new form importnamespaceQualifiedName*::**; that recursively imports the members of namespaces contained in the the namespace given by namespaceQualifiedName, but does not include the direct members of the given namespace itself.
   c. Import All. Using the keywords import all rather than just import now imports memberships without regard to visibility.
2. Implies operator. The symbol => can now be used as an alternative operator for implies.
3. Feature Value Defaults. As previously, the feature value notation feature=expression; declares that a feature is bound to the result of the given expression (using a binding connector). This means that a redefinition of the feature that binds it to a different result will usually be semantically inconsistent. It is now possible to instead declare a default feature value using the form featuredefault=defaultExpression; or featuredefaultdefaultExpression;. In this case, unless the default is overridden, the actual binding of the feature to the result of the default expression is deferred until the containing type is instantiated. The default can be overridden in a redefinition of the feature, either with a new default or a non-default binding.
4. Feature Chaining. A feature chain is a sequence of feature references represented using dot notation of the form f_1.f_2. ... .f_n (similar to a property path in SysML v1). Feature chains of this form can now be used as the targets of subsetting and redefinition relationships, as well as to specify the ends of connectors and the sources and targets of flows. (Dot notation can also still be used in expressions to represent the more general form of a path step expression.)

KerML Only

1. Feature Chains. The notation featurememberNameisf_1.f_2. ... .f_n; can be used to declare a named feature specified by a feature chain.
2. Negated Invariants. The syntax for Invariants has been extended to allow inv true and inv false, to declare Boolean expressions that are invariantly true or invariantly false, respectively. inv true is the default, corresponding to the current inv syntax.
3. Disjoining. The notation disjoiningidentificationdisjointtypeDisjoinedfromdisjoiningType; indicates that type given by typeDisjoined is disjoint from the type given by disjoiningType (the disjoiningidentification part is optional). That is, it declares that no instance of typeDisjoined is also classified by disjoiningType. One or more such disjoining relationships can also be included directly in the declaration of the typeDisjoined, using the notation featuretypeDisjoineddisjoint fromdisjoiningType,disjoiningType... ; (the disjoint from part comes after any specialization part, but before a featured by part).
4. Feature members. Adding the keyword member to the start of a feature declaration contained in a type now indicates that the feature is owned via a membership relationship, not a feature membership. That is, while the feature will be declared in the namespace of the containing type, it will not be featured by that type and will, instead, be featured by Anything, unless the feature declaration includes an explicit featured by part.

SysML Only

1. Ports. Port definitions and usages are now considered to be kinds of occurrence definitions and usages. This allows then to, e.g., be used as the target of an event declaration.
2. Perform Actions. Perform action usages are now considered to be kinds of event occurrence usages.
3. Reference Usages. Previously, a usage declaration without a kind keyword defaulted to an attribute usage. For example mass : MassValue; was equivalent to attributemass : MassValue;. The default has now been changed to a reference usage, so that mass : MassValue; is now equivalent to refmass : MassValue; For a usage of an attribute definition this is semantically equivalent to the previous default (since attribute usages are always referential), but it also allows referential usages of any other kind of definition to be declared using the default form. (Composite usages must still be declared using the appropriate kind keyword.)
4. Assert Constraint Usages. The notation for assert constraint usages has been extended to also allow assert not, meaning that the constraint is asserted to be false instead of true.
5. Satisfy Requirement Usages. The notation for satisfy requirement usages has been extended to allow it to start with an optional assert keyword, to emphasize that it is a kind of constraint assertion. In addition, the not keyword can be added in front of satisfy to indicate that a requirement is not satisfied. That is, satisfyrequirementbysubject; and assert satisfyrequirementbysubject; both assert that subject satisfies requirement, while not satisfyrequirementbysubject; and assert not satisfyrequirementbysubject; assert that subject does not satisfy requirement.
6. Multiplicity Defaults. Previously, when a usage was declared without an explicit multiplicity, the multiplicity was inherited from any implicit or explicit subsetted features. Since all the base features from the library have the most general multiplicity 0..*, this meant that 0..* was the effective default multiplicity if no more constraining multiplicity was given. Now, a default multiplicity of 1..1 is automatically added to attribute usages, item usages (including part usages, but not connection usages) and port usages, if both of the following conditions are met (if a default is not added, then the multiplicity is inherited, as previously):
   • The usage is owned by a type (i.e., a definition or usage, not a package).
   • The usage does not have any explicit subsettings or redefinitions.
7. Parallel States. A state definition or usage can now be declared to be a parallel state by placing the keyword parallel before the start of its body, e.g., state defNameparallel{ ... } or statename:Definitionparallel{ ... }. A parallel state is one for which all its nested states run concurrently ("in parallel"). Therefore, a parallel state is not allowed to contain any successions or transitions that restrict the performance of its nested states.
8. State Subactions. Previously, entry, do and exit actions had to appear at the very beginning of the body of a state definition or usage. Now they may appear anywhere in the body, in any order (but at most one of each).
9. Use Cases. Use cases have now been added to the language as kinds of cases. Use case definitions and usages can be declared using the keywords use case def and use case, respectively. Included use case usages can be specified with a notation similar to perform action usages, but using the keyword include instead of perform. (The traditional use case "extend" relationship has not yet been implemented.)
10. Actors. Actors can be declared as special parameters of requirements and cases (not just use cases), similarly to the way the subject of a requirement or case is declared. An actor parameter is declared as a part usage, but using the keyword actor instead of part, i.e., with the form actorusageDeclaration;. A requirement or case can have multiple actor parameters.
11. Connections. Previously, binding connectors, successions and item flows were adopted into the SysML language directly from KerML. This has been updated so, when they are used in SysML, they are considered to be SysML usages. This means that these elements can now participate in variant modeling, individual modeling, etc, just like other SysML usages.

Model Library

Kernel Library

1. Scalar Values. The Number types have been updated so that Real specializes Complex, Rational specializes Real and Integer specializes Rational. The relevant functions packages have also been updated to remove up-conversion functions that are no longer necessary.
2. Exponentiation. Missing specializations of of '^' have been added to all those Kernel Library functions packages that already include '**'.

Systems Library

1. Use Cases. A library package has been ...

2021-06 - SysML v2 Pilot Implementation

This is an incremental update to the 2021-05 release. It corresponds to Eclipse plugin version 0.14.0.

Language features

KerML and SySML

1. Import.
   a. Member Import. Single member import is no longer equivalent to aliasing. The notation importnamespaceQualifiedName::elementName; now imports the membership in the imported namespace given by namespaceQualifiedName whose member name is given by elementName. This works properly even if given elementName is an alias name. If namespaceQualifiedName is not given, then elementName is resolved in the containing scope of the import.
   b. Recursive Import. As previously, a recursive import of the form importnamspaceQualifiedName::**; includes the members of the namespace given by namespaceQualifiedName as well as members recursively imported from namespaces contained in the given namespace. There is now also a new form importnamspaceQualifiedName*::**; that recursively imports the members of namespaces contained in the the namespace given by namspaceQualifiedName, but does not include the direct members of the given namespace itself.
   c. Import All. Using the keywords import all rather than just import now imports memberships without regard to visibility.
2. Implies operator. The symbol => can now be used as an alternative operator for implies.
3. Feature Value Defaults. As previously, the feature value notation feature=expression; declares that a feature is bound to the result of the given expression (using a binding connector). This means that a redefinition of the feature that binds it to a different result will usually be semantically inconsistent. It is now possible to instead declare a default feature value using the form featuredefault=defaultExpression; or featuredefaultdefaultExpression;. In this case, unless the default is overridden, the actual binding of the feature to the result of the default expression is deferred until the containing type is instantiated. The default can be overridden in a redefinition of the feature, either with a new default or a non-default binding.
4. Feature Chaining. A feature chain is a sequence of feature references represented using dot notation of the form f_1.f_2. ... .f_n (similar to a property path in SysML v1). Feature chains of this form can now be used as the targets of subsetting and redefinition relationships, as well as to specify the ends of connectors and the sources and targets of flows. (Dot notation can also still be used in expressions to represent the more general form of a path step expression.)

KerML Only

1. Feature Chains. The notation featurememberNameisf_1.f_2. ... .f_n; can be used to declare a named feature specified by a feature chain.
2. Negated Invariants. The syntax for Invariants has been extended to allow inv true and inv false, to declare Boolean expressions that are invariantly true or invariantly false, respectively. inv true is the default, corresponding to the current inv syntax.
3. Disjoining. The notation disjoiningidentificationdisjointtypeDisjoinedfromdisjoiningType; indicates that type given by typeDisjoined is disjoint from the type given by disjoiningType (the disjoiningidentification part is optional). That is, it declares that no instance of typeDisjoined is also classified by disjoiningType. One or more such disjoining relationships can also be included directly in the declaration of the typeDisjoined, using the notation featuretypeDisjoineddisjoint fromdisjoiningType,disjoiningType... ; (the disjoint from part comes after any specialization part, but before a featured by part).
4. Feature members. Adding the keyword member to the start of a feature declaration contained in a type now indicates that the feature is owned via a membership relationship, not a feature membership. That is, while the feature will be declared in the namespace of the containing type, it will not be featured by that type and will, instead, be featured by Anything, unless the feature declaration includes an explicit featured by part.

SysML Only

1. Ports. Port definitions and usages are now considered to be kinds of occurrence definitions and usages. This allows then to, e.g., be used as the target of an event declaration.
2. Perform Actions. Perform action usages are now considered to be kinds of event occurrence usages.
3. Reference Usages. Previously, a usage declaration without a kind keyword defaulted to an attribute usage. For example mass : MassValue; was equivalent to attributemass : MassValue;. The default has now been changed to a reference usage, so that mass : MassValue; is now equivalent to refmass : MassValue; For a usage of an attribute definition this is semantically equivalent to the previous default (since attribute usages are always referential), but it also allows referential usages of any other kind of definition to be declared using the default form. (Composite usages must still be declared using the appropriate kind keyword.)
4. Assert Constraint Usages. The notation for assert constraint usages has been extended to also allow assert not, meaning that the constraint is asserted to be false instead of true.
5. Satisfy Requirement Usages. The notation for satisfy requirement usages has been extended to allow it to start with an optional assert keyword, to emphasize that it is a kind of constraint assertion. In addition, the not keyword can be added in front of satisfy to indicate that a requirement is not satisfied. That is, satisfyrequirementbysubject; and assert satisfyrequirementbysubject; both assert that subject satisfies requirement, while not satisfyrequirementbysubject; and assert not satisfyrequirementbysubject; assert that subject does not satisfy requirement.
6. Multiplicity Defaults. Previously, when a usage was declared without an explicit multiplicity, the multiplicity was inherited from any implicit or explicit subsetted features. Since all the base features from the library have the most general multiplicity 0..*, this meant that 0..* was the effective default multiplicity if no more constraining multiplicity was given. Now, a default multiplicity of 1..1 is automatically added to attribute usages, item usages (including part usages, but not connection usages) and port usages, if both of the following conditions are met (if a default is not added, then the multiplicity is inherited, as previously):
   • The usage is owned by a type (i.e., a definition or usage, not a package).
   • The usage does not have any explicit subsettings or redefinitions.
7. Parallel States. A state definition or usage can now be declared to be a parallel state by placing the keyword parallel before the start of its body, e.g., state defNameparallel{ ... } or statename:Definitionparallel{ ... }. A parallel state is one for which all its nested states run concurrently ("in parallel"). Therefore, a parallel state is not allowed to contain any successions or transitions that restrict the performance of its nested states.
8. State Subactions. Previously, entry, do and exit actions had to appear at the very beginning of the body of a state definition or usage. Now they may appear anywhere in the body, in any order (but at most one of each).
9. Use Cases. Use cases have now been added to the language as kinds of cases. Use case definitions and usages can be declared
   using the keywords use case def and use case, respectively. Included use case usages can be specified with a notation similar to perform action usages, but using the keyword include instead of perform. (The traditional use case "extend" relationship has not yet been implemented.)
10. Actors. Actors can be declared as special parameters of requirements and cases (not just use cases), similarly to the way the subject of a requirement or case is declared. An actor parameter is declared as a part usage, but using the keyword actor instead of part, i.e., with the form actorusageDeclaration;. A requirement or case can have multiple actor parameters.
11. Connections. Previously, binding connectors, successions and item flows were adopted into the SysML language directly from KerML. This has been updated so, when they are used in SysML, they are considered to be SysML usages. This means that these elements can now participate in variant modeling, individual modeling, etc, just like other SysML usages.

Model Library

Kernel Library

1. Scalar Values. The Number types have been updated so that Real specializes Complex, Rational specializes Real and Integer specializes Rational. The relevant functions packages have also been updated to remove up-conversion functions that are no longer necessary.
2. Exponentiation. Missing specializations of of '^' have been added to all those Kernel Library functions packages that already include '**'.

Systems Library

1. Use Cases. A library package has been added forUseCases, with base definition UseCase and base usage useCases.
2. Actors. An actors feature has been added to Cases::Case and Requirements::Requirement.
3. Items and Parts. There have been updates to some of the features in the Item and Part definitions.
4. Ports. Port now specializes Occurrence and ports n...