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OMG System Modeling Language — Open Issues

  • Acronym: SysML
  • Issues Count: 18
  • Description: Issues not resolved
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Issues Descriptions

Figures 15.5 and 15.6 diagram types

  • Key: SYSML17-89
  • Legacy Issue Number: 18459
  • Status: open  
  • Source: NIST ( Conrad Bock)
  • Summary:

    Figures 15.5 (Example of flow allocation from ObjectFlow to Connector) and 15.6 (Example of flow allocation from ObjectFlow to ItemFlow) have ibds on the right, but those ibds have blocks instead of parts in them. Are they supposed to be a bdds? The blocks show parts, but the compartment doesn't say "structured" (same for Figure 15.8).

  • Reported: SysML 1.3 — Fri, 15 Feb 2013 05:00 GMT
  • Updated: Thu, 2 Jul 2020 12:57 GMT

Figure 15.8 diagram type

Don't use the optional notation for Pins with Allocation

  • Key: SYSML17-93
  • Legacy Issue Number: 18502
  • Status: open  
  • Source: PTC ( Phillip Astle)
  • Summary:

    Figure C.35 uses the optional notation for Pins (i.e. >[]> instead of []->[]). The allocation callout note is anchored to the object node symbol which makes it ambiguous as to which dictionary item(s) are being allocated. It could be one of the following:

    + the origin and destination pins
    + the object flow
    + the common type of the pins

    Since it's unclear what is being allocated, it would make more sense to show the Pins on the diagram and link the callout note to the relevant item(s) (I believe it's supposed to go to the ObjectFlow).

  • Reported: SysML 1.3 — Tue, 26 Feb 2013 05:00 GMT
  • Updated: Wed, 1 Jul 2020 12:08 GMT

Convention for enumeration not used for ControlValue

  • Legacy Issue Number: 19134
  • Status: open  
  • Source: oose Innovative Informatik eG ( Tim Weilkiens)
  • Summary:

    The convention

    Enumeration types: always end with “Kind” (e.g., “DependencyKind”)

    is not used for the ControlValue enumeration. It should be named ControlValueKind.

  • Reported: SysML 1.3 — Thu, 5 Dec 2013 05:00 GMT
  • Updated: Mon, 15 Jun 2020 05:11 GMT

Contradiction regarding allowed use of the derived indicator for constraint parameters

  • Key: SYSML17-77
  • Legacy Issue Number: 17546
  • Status: open  
  • Source: Delligatti Associates, LLC ( Lenny Delligatti)
  • Summary:

    There is a contradiction in the SysML spec. regarding whether constraint parameters-as properties of constraint blocks-may use the derived indicator, "/".

    Pg. 84 of the spec. clearly states the original intent of the SysML Development Team with respect to constraint blocks: "The block constraints are non-causal and do not specify the dependent or independent variables. The specific dependent and independent variables are often defined by the initial conditions, and left to the computational engine."

    On pg. 86, however, the spec. states textually that constraint parameters are properties of constraint blocks: "All properties of a constraint block are constraint parameters, with the exception of constraint properties that hold internally nested usages of other constraint blocks."

    There is no metamodel fragment in the spec. that shows that the stereotype SysML::ConstraintParameter extends the metaclass UML4SysML::Property. The text on pg. 86 (quoted above) conveys this.

    As a result of this (implied) extension relationship, we would have to conclude that a constraint parameter could use the derived indicator, "/", to convey that it is a dependent variable in the constraint expression.

    This stands in contradiction, however, to the intended non-causal, non-directional nature of constraint blocks as expressed on pg. 84.

    Proposed Resolutions:

    1) Add a metamodel fragment to the spec. that clearly shows the extension relationship from SysML::ConstraintParameter to UML4SysML::Property.
    2) Add a constraint to the SysML::ConstraintParameter stereotype disallowing the use of the derived indicator, "/", on constraint parameters.

  • Reported: SysML 1.3 — Wed, 8 Aug 2012 04:00 GMT
  • Updated: Thu, 28 May 2020 16:09 GMT

Missing type constraints for FullPort

  • Key: SYSML17-81
  • Legacy Issue Number: 18182
  • Status: open  
  • Source: PTC ( Phillip Astle)
  • Summary:

    Ports stereotyped as FullPort can currently be typed by anything a normal Port can be typed by. This isn't the intent of the specification, so constraints should be added.

  • Reported: SysML 1.3 — Fri, 19 Oct 2012 04:00 GMT
  • Updated: Mon, 20 Apr 2020 08:10 GMT

Inability to specify partial allocation and requriements satisfaction

  • Key: SYSML17-86
  • Legacy Issue Number: 18434
  • Status: open  
  • Source: INCOSE ( Sanford Friedenthal)
  • Summary:

    The allocate and requirements relationships (e.g., satisfy, verify, derive) do not explicitly state the degree to which these relationships apply. For example, a satisfy relationship may imply a model element may fully satisfy, partially satisfy, or not satisfy at all a particular requirement at a point in the design process. However, there is no standard way to refer to this partial vs complete satisfaction. A similar issue applies to the verify and derive relationships.

    Note: Similar issues apply to allocate relationships where the allocate may indicate that the element is fully or partially allocated to another element.

    The SysML spec should consider incorporating a tagged value to indicate 0, partial or complete on these relationships.

  • Reported: SysML 1.3 — Fri, 8 Feb 2013 05:00 GMT
  • Updated: Tue, 23 Apr 2019 00:20 GMT

Property Based Requirements

  • Key: SYSML17-71
  • Legacy Issue Number: 17016
  • Status: open  
  • Source: Lockheed Martin ( John Watson)
  • Summary:

    In SysML today requirements can be represented in a model only in a textual form. Being textually based these requirements often introduce ambiguity, are often redundant with other model element properties, and lack a formally making it difficult to leverage directly in parametric and other analysis efforts.
    This issue suggests an alternative means of representing requirement in the model environment without using a pure text string. The alternative means is referred to as Property Based Requirement (PBR). PBR defines a requirement mathematically and defines a set of requirement properties. The goal is declare other types of model elements as requirements and apply these properties to those model elements.

    A PBR theory is described in a paper called “Toward a Property Based Requirements Theory: System Requirements Structured as a Semilattice” by Patrice Micouin. This technique is further elaborated in a paper called “Requirements Management within a Full Model-Based Engineering Approach” by Yves Bernard

  • Reported: SysML 1.3 — Thu, 19 Jan 2012 05:00 GMT
  • Updated: Tue, 23 Apr 2019 00:20 GMT

InstanceSpecification equality

  • Key: SYSML17-67
  • Legacy Issue Number: 16653
  • Status: open  
  • Source: NASA ( Nicolas Rouquette)
  • Summary:

    Multiple InstanceSpecifications can describe overlapping sets of instances, and some application need to specify whether the sets overlap. For InstanceSpecifications that specify exactly one instance, this indicates whether they describe the same instance, like the sameAs stereotype in the Ontology Definition Metamodel.

  • Reported: SysML 1.3 — Mon, 7 Nov 2011 05:00 GMT
  • Updated: Tue, 23 Apr 2019 00:20 GMT

InstanceSpecifications for exactly one instance

  • Key: SYSML17-66
  • Legacy Issue Number: 16652
  • Status: open  
  • Source: NASA ( Nicolas Rouquette)
  • Summary:

    InstanceSpecifications describe sets of instances, including the empty set, but some applications need to describe exactly one instance. SysML should have InstanceSpecifications that are constrained to describe exactly one instance, like the owlIndividual stereotype in the Ontology Definition Metamodel.

  • Reported: SysML 1.3 — Mon, 7 Nov 2011 05:00 GMT
  • Updated: Tue, 23 Apr 2019 00:20 GMT

Diagram show inconsistent data

  • Key: SYSML17-94
  • Legacy Issue Number: 18503
  • Status: open  
  • Source: PTC ( Phillip Astle)
  • Summary:

    Diagrams C.35, C.36 and C.37 show inconsistent allocation between the displayed items, yet the text would seem to imply that they're supposed to show the same relationships.

    In C.35, the allocation is from an ObjectNode symbol called "DriveCurrent" (which I believe equates to an ObjectFlow - name unknown) to an ItemFlow called "i1".

    In C.36, the allocation is from an ObjectNode called "DriveCurrent" to a Connector (name unknown).

    In C.37, the allocation is from an ObjectFlow called "o6" to a Connector called "epc-emg.1".

    There are a number of issues:

    1. ObjectNode is an abstract specialization of ActivityNode and as such you can't have any instances of them in a model. Any reference to an ObjectNode should be removed.

    2. The allocation should consistently be from ObjectFlow "o6" to either ItemFlow "i1" or Connector "epc-emg.1".

    3. In order to make it clear that the same items are being related, the names of the ObjectFlow and the Connector/ItemFlow should be shown on all diagrams. Currently the ObjectFlow and the Connector names are not shown.

  • Reported: SysML 1.3 — Tue, 26 Feb 2013 05:00 GMT
  • Updated: Fri, 5 Apr 2019 22:12 GMT

Clarification required for Copy relationship

  • Key: SYSML17-95
  • Legacy Issue Number: 18525
  • Status: open  
  • Source: PTC ( Phillip Astle)
  • Summary:

    There's a few issues with the Copy relationship as described in the specification.

    1. It's unclear what constraint 3 means. What are subrequirements (nested or derived)?

    2. How do you match subrequirements in the slave to subrequirements in the master?

    3. There's no constraint on the number of Copy relationships that a slave Requirement can be involved in (e.g. one Requirement could be the slave of two different master Requirements). What happens to the "text" tag if there are multiple masters?

    4. There's no constraint stopping a Requirement from being directly or indirectly a master of itself. Shouldn't there be?

  • Reported: SysML 1.3 — Mon, 4 Mar 2013 05:00 GMT
  • Updated: Thu, 24 Jan 2019 17:02 GMT

Allocated notation on object nodes missing from diagram elements table

  • Key: SYSML17-91
  • Legacy Issue Number: 18461
  • Status: open  
  • Source: NIST ( Conrad Bock)
  • Summary:

    In Allocations, the Diagram Element table is missing the notation for allocated object nodes shown in Figure 15.7 (Example of flow allocation from ObjectNode to FlowProperty).

  • Reported: SysML 1.3 — Fri, 15 Feb 2013 05:00 GMT
  • Updated: Thu, 24 Jan 2019 16:45 GMT

Allocation tabular notation normative?

  • Key: SYSML17-90
  • Legacy Issue Number: 18460
  • Status: open  
  • Source: NIST ( Conrad Bock)
  • Summary:

    The clause Allocations, Usage Example, Tabular Representation is in the normative part of the spec, but refers to a tabular notation in Annex C, which isn't normative. Is the tabular notation normative?

  • Reported: SysML 1.3 — Fri, 15 Feb 2013 05:00 GMT
  • Updated: Thu, 24 Jan 2019 16:41 GMT

Missing ownership constraints

  • Key: SYSML17-80
  • Legacy Issue Number: 18181
  • Status: open  
  • Source: PTC ( Phillip Astle)
  • Summary:

    The FlowProperty stereotype can current be applied to any Property in SysML. However, this leaves it open to applying the stereotype to Ports (inc. extensions of Ports) and Properties owned by non-Blocks. This doesn't seem to match the intent of the specification so constraints need to be added

  • Reported: SysML 1.3 — Fri, 19 Oct 2012 04:00 GMT
  • Updated: Thu, 24 Jan 2019 16:38 GMT

Callout notation for port-specific types and initial values

  • Key: SYSML17-75
  • Legacy Issue Number: 17406
  • Status: open  
  • Source: oose Innovative Informatik eG ( Axel Scheithauer)
  • Summary:

    The specification allows property-specific types and property-specific initial values. Ports are just a special kind of property. Thus it would be possible to model port-specific types and values. The only problem is, that it is not possible to show the specifics of these types or the initial values within an internal block diagram, as would be the case for a property.

    Suggested addition to the spec

    • property-specific types and initial values also apply to ports [would not be forbidden now, but just to clarify this point]
    • A callout notation can be used in an ibd for ports with a port-specific type or initial value. It shows the same information as the compartments for properties.
    • Table 8.3: Example for call-out notation

    Maybe this notation could also be used on block definition diagrams, and in this case for properties as well. Then there should be a sentence in chapter and an example in Table 8.2.

  • Reported: SysML 1.3 — Tue, 5 Jun 2012 04:00 GMT
  • Updated: Thu, 17 Jan 2019 14:45 GMT

Unclear is StructuredActivityNode owned Actions should be Allocated

  • Key: SYSML17-99
  • Legacy Issue Number: 18678
  • Status: open  
  • Source: PTC ( Phillip Astle)
  • Summary:

    In the Constraints section the specification states the following:

    'An Action appearing in an “AllocateActivityPartition” will be the /client (from) end of an “allocate” dependency. The element that represents the “AllocateActivityPartition” will be the /supplier (to) end of the same “allocate” dependency.'

    For Actions owned by an Activity and shown inside the partition, this constraint is clear. However, if you have a StructuredActivityNode inside a partition and that StructuredActivityNode owns an Action, how many Allocate dependencies should there be? Should there be:

    a) One allocate from the StructuredActivityNode only?
    b) One allocate dependency from the StructuredActivityNode and one from the Action inside the StructuredActivityNode?

    To make things clearer, instead of the constraints section saying:

    'An Action appearing IN an "An Action appearing in an “AllocateActivityPartition”'

    It should say something along the lines of:

    'An Action referenced in the "node" role of an “AllocateActivityPartition”'

    This would remove the ambiguity of what "in" means and allow users to decide when Allocate dependencies are created.

  • Reported: SysML 1.3 — Fri, 19 Apr 2013 04:00 GMT
  • Updated: Sun, 13 Jan 2019 15:32 GMT

Libraries package should be named "SysML Model Libraries"

  • Key: SYSML17-92
  • Legacy Issue Number: 18462
  • Status: open  
  • Source: NIST ( Conrad Bock)
  • Summary:

    The spec headings refer to model libraries using the adjective "model", so the package name should include it also. The name should start with "SysML" since it is separate from the SysML package.

  • Reported: SysML 1.3 — Sun, 17 Feb 2013 05:00 GMT
  • Updated: Sun, 13 Jan 2019 15:32 GMT