OMG SysML — Systems Modeling Language
How the OMG SysML standard relates to NexoGraph entities and traceability relations.
Systems Modeling Language (SysML) is an OMG-standardized general-purpose modeling language for systems engineering. It extends UML 2 with systems engineering concepts — blocks, flows, constraints, and requirements — and is the de facto notation used in MBSE tool implementations. SysML v2 (2024) is a complete redesign with formal semantics and a new Kernel Modeling Language (KerML).
NexoGraph's metamodel is structurally aligned with SysML's requirement and dependency concepts, though it does not produce formal SysML notation.
Diagram Types
SysML 1.x (UML-profile based)
| Diagram | Abbreviation | Purpose |
|---|---|---|
| Block Definition Diagram | BDD | Structural decomposition — system hierarchy, properties, ports |
| Internal Block Diagram | IBD | Internal connections between parts of a block |
| Package Diagram | PKG | Namespace and model organization |
| Requirements Diagram | REQ | Requirements and <<satisfy>>/<<verify>> dependency relations |
| Parametric Diagram | PAR | Constraint-based mathematical relations between parameters |
| Use Case Diagram | UC | System boundary and actor interactions |
| Activity Diagram | ACT | Behavior as data/control flows |
| Sequence Diagram | SEQ | Time-ordered message exchange |
| State Machine Diagram | STM | State-based behavior of a block |
SysML v2 (KerML-based, 2024)
SysML v2 replaces the UML profile with a ground-up formal metamodel and Kernel Modeling Language (KerML). It adds first-class support for analysis cases, verification cases, and a textual notation (.sysml files). The structural concepts (Part, Port, Connection, Requirement) carry over but with stronger typing and semantics.
Requirements in SysML
The SysML Requirements Diagram and its dependency stereotypes directly correspond to the NexoGraph traceability model:
| SysML stereotype | Meaning | NexoGraph equivalent |
|---|---|---|
<<requirement>> | A verifiable condition | Requirement entity |
<<stakeholderRequirement>> | A need expressed by a stakeholder | StakeholderNeed entity |
<<deriveReqt>> / refinement | A need or model element is refined into a requirement | Need → Requirement via REFINES_INTO |
<<refine>> | A model element further specifies a requirement | StakeholderNeed → UserNeed traceability |
<<satisfy>> | A design element satisfies a requirement | Architectural allocation (future) |
<<verify>> | A test case verifies a requirement | Verification link (gap — not yet in metamodel) |
<<copy>> | A requirement is copied from another | — |
NexoGraph Alignment
Structure
| SysML concept | NexoGraph implementation |
|---|---|
| Package (namespace) | Package entity — hierarchical, typed via PackageType |
| Block (system element) | Not yet modelled — architectural decomposition is a planned layer |
| Part (instantiated block) | Not yet modelled |
| Port / Flow | Not yet modelled |
| Constraint / Parametric | Not yet modelled |
Requirements and traceability
| SysML concept | NexoGraph implementation |
|---|---|
<<requirement>> with id, text | Requirement entity — uuid, shortId, reqText |
<<stakeholderRequirement>> | StakeholderNeed entity — needText, rationale, source |
| Requirement hierarchy (parent/child) | Package hierarchy groups related requirements; order field within a package |
<<deriveReqt>> / refinement (need → req) | Implemented as need-refines-into-stakeholder-requirement (REFINES_INTO) |
<<satisfy>> (design → req) | Planned — architectural allocation layer |
<<verify>> (test → req) | Gap — verification link not yet in metamodel |
<<refine>> (need → need) | Partially covered by User → UserNeed → UserStory chain |
Gap Analysis
| SysML feature | NexoGraph status |
|---|---|
| Block / Part / Port model | Not implemented — structural decomposition planned for post-MVP |
| IBD (internal connections) | Not implemented |
| Parametric diagram | Not implemented |
<<satisfy>> allocation relation | Planned |
<<verify>> relation | Planned |
| Verification method on Requirement | Planned (see ISO 29148 gaps) |
| SysML 1.x export (XMI) | Not implemented |
| SysML v2 textual notation export | Not implemented |
SysML v2 and NexoGraph
SysML v2 introduces a textual notation and API-first model exchange format. NexoGraph's graph-native model is well-suited for eventual SysML v2 round-trip exchange: NexoGraph entities map to SysML v2 features, reference relations map to SysML v2 relationships, and root collections map to SysML v2 packages. Formal SysML v2 import/export is a planned long-term capability.