2021-05 - SysML v2 Pilot Implementation

This is an incremental update to the 2021-04 release. It corresponds to Eclipse plugin version 0.13.0.

Language features

Occurrences

1. Occurrences. An occurrence is something that has a life over time and possibly a spacial extent. In SysML v2, items, actions and constraints (and their further specializations) are all kinds of occurrences (but attributes are not). It is now possible to model an occurrence without committing to what kind of occurrence it is using the definition and usage notations occurrence def and occurrence.
2. Individuals. The syntax for individuals has been expanded.
   • Individual definitions and usages can now be made on all kinds of occurrences, i.e., individual part def/individual part, individual action def/individual action, etc.
   • The notations individual def and individual default to individual occurrence def and individual occurrence.
   • Every individual usage of any kind must have exactly one type that is an individual definition. However, individual usages may now also have additional types that are not individual definitions.
3. Time slices and snapshots. The time slice and snapshot notation has been updated.
   • The timeslice and snapshot notations are no longer restricted to individuals, allowing any kind of occurrence type. The kind of occurrence can be explicitly given in the declaration, e.g., timeslice part, snapshot action, etc.
   • A timeslice or snapshot usage without an explicit type that is nested in the body of occurrence definition or usage (of any kind) is implicitly a time slice or snapshot of its containing occurrence.
   • A timeslice or snapshot usage with a type that is an individual definition implicitly represents a time slice or snapshot of the defined individual. To make a timeslice or snapshot declaration explicitly an individual usage, the notations individual timeslice and individual snapshot can be used.
4. Event occurrences. A notation has been added for event occurrences.
   • The notation event occurrencename; represents an identified suboccurrence of a containing occurrence. That is, it is equivalent to ref occurrencename:> suboccurrences;.
   • The notation eventqualifedName; declares an event occurrence by reference to an occurrence usage owned elsewhere. It is equivalent to ref occurrence:>qualifiedName:> suboccurrences;.
   • The event occurrence notation can be considered a generalization of perform action and exhibit state. However, unlike perform and exhibit, the referential event notation does not take its effective name from the occurrence usage it references. This is because it is expected that event will commonly be used to reference the source and target of messages (see below), which would result in name conflicts between multiple such events in one namespace.
5. Messages. A notation has been added for messages, which are item flows without explicitly specified sourceOutput and targetInput features.
   • Messages are notated as special kinds of connectors: messagenameofFlowTypefromsourcetotarget;. The name and FlowType are optional.
   • As an item flow, the implicit type of a message is the Kernel library type Transfer. A message can also be explicitly typed with any specialization of Transfer.

Logical Expressions

6. Exclusive or. The exclusive-or operator has been changed from ^ to ^^. This allows ^ to be used as an exponentiation operator. (The existing ** exponentiation operator has also been retained for now.)
7. Keyword operators. Keywords have been introduced as alternatives for certain existing symbolic operators.

Keyword	Symbol
and	&&
or	||
xor	^^
not	!

8. Implies. A new implies operator has been add for logical implication. Note that this is a conditional operator: the expression ximpliesy is equivalent to notxory or !x||y. That is, if x evaluates to false, then y is not evaluated and the implication results in true.
9. Conditional. A new syntax iftest? xelsey has been introduced as an alternative for the conditional expression test?x:y.

Library Models

10. State space representation. The StateSpaceRepresentation package in the Analysis Domain Library has been updated to use vector quantities.
11. Feature access and control performances. A new FeatureAccessPerformances package has been added to the Kernel Library, and the ControlPerformances package has been updated with base behavior for conditional and looping constructs. However, the abstract and contract syntax have not been updated to take advantage of these new models yet.

Backward incompatibilities

1. Keywords. The following new keywords have been added as reserved words:
   • KerML: and implies not or xor
   • SysML: and event implies message not occurrence or xor
2. Exclusive or. The operator symbol for exclusive or is now ^^ rather than ^. The operator symbol ^ now denotes exponentiation.
3. Precedence. The precedence of the logical operators has been changed so that and and && have the same precedence as &, and or and || have the same precedence as |. The precedence of implies is lower than the or operators.
4. Transfer ends. The ends of a Transfer have been renamed from transferSource/transferTarget to source/target. This means that the ends of a named message can be referenced as messageName::source and messageName::target (e.g., when used with the event notation).

Visualization

1. Tom Sawyer
   • Big fixes.
     
2. PlantUML
   • Updated the visualization of individuals, snapshots and time slices.

Bug Fixes

1. Dot notation. Allowed the new "dot notation" to be used to specify the ends of item flows.
2. Name hiding. Fixed a bug that could cause other scope names to be hidden when using filtered import.
3. Visualization.
   • Fixed bugs in the Tom Sawyer tool that could case initial loading of diagrams to be empty and disabled the the load project action if the web page was refreshed.
   • Fixed a bug in the PlantUML visualization that caused referential features to be rendered using black-diamond (composite) notation.
4. XMI export. Fixed a bug in the XMI export utility that sometimes caused member names not to be written to the XMI file.

Technical Improvements

1. Eclipse 2021-03. The pilot implementation is now being developed and tested using Eclipse 2021-03 and Java 11.
2. XMI utility. The XMI export utility has been updated to use element UUIDs as XMI IDs, rather than using the default xpath mechanism for cross-references.
3. Syntax highlighting. The utility that generates syntax highlighting files from the Xtext grammars has been updated to automatically generate the Jupyter highlighting configuration.