SYSML11 — Chapter 8, Blocks, instance specifications for default values

The exclusion of UML concrete syntax for Instance Specifications has resulted in the inability to assign default values to properties of blocks using anything other than simple text strings for value properties. Consider reintroducing UML concrete syntax for UML InstanceSpecification into one or more SysML diagram types so that more complex default values can be assigned.

Change the specification of the defaultValue compartment to base its internal metamodel representation on UML InstanceValue, and to decouple the representation of context-specific property values entirely from property-specific types. Also rename the compartment to "initialValues" to more accurately indicate the ability of these compartments to provide values which are assigned in a local property-specific context to override of any existing default or initial values defined on underlying blocks that may type a property.
As background, this issue was previously deferred by the FTF with the following discussion comments:
The defaultValue compartment on an internal block diagram does provide at least one available option for assigning default values to structured values, as discussed in the subsection "Default value compartment" under 8.3.1.3 Internal Block Diagram. Creating a graphical compartment on an internal block diagram to assign values to properties defined on a block definition diagram may be more cumbersome than a textual syntax, but tools may be able to streamline the linkage to the default value for usability. In particular, the use of a "structure" compartment on a block definition would allow the default value to be shown next to a properties compartment where a property is defined.
Other work in OMG is currently underway that may define a standardized form of textual syntax for value specifications. SysML could consider such a textual syntax for property values in future versions.
The scope of this resolution is to clarify the graphical syntax and internal metamodel for the "initialValues" compartment that may be shown on properties on an internal block diagram. Other issues, such as 12277 and 12353, request additional support for display of context-specific values using forms of concrete syntax for UML InstanceSpecification or else additional forms of compartments on properties on an ibd. These issues are being deferred, but can be reconsidered in the future following this initial step to clarify the initialValues compartment, as included in the scope of this resolution. Other forms of textual syntax for complex values, such as the MARTE Value Specification Language (VSL), could also be considered by future issue resolutions following the current RTF.
Issue 11502, "PropertySpecificType concept is highly ineffective and suboptimal," has its own resolution of Closed, no change, but this resolution is based partly on the ability of the initialValues compartment to remove one of the major reasons why property-specific types might need to be used. Instead, use of the more complicated property-specific type mechanism can be reserved for cases in which new or redefined features are really needed in a new specialized property-specific type, rather than merely an assignment of local values. See the resolution for Issue 11502 for more information.
Issues 12361, "defaultValue should be renamed initialValue(s)," and 12363, "Decouple 'values' compartment for a part Property in an IBD from PropertySpecificType" record some of the history of working discussions by the RTF on the defaultValue compartment issue, as well as additional perspective. All specific changes to the specification are being consolidated under this issue, so these two other issues are being closed as having their resolutions merged under this one.