Overview
A System Element is a work item that represents a physical or functional component within your system hierarchy. In the Aerospace Safety Solution, system elements serve multiple critical roles:- Architectural decomposition — Breaking down a complex system (e.g., Flight Control Computer) into subsystems, assemblies, and components
- Document organization — Grouping requirements, design specs, FMEA analyses, and test documentation by system element
- Traceability anchor — Serving as the reference point for linking failure conditions, failure modes, characteristics, and risk controls
- DAL assignment — Allocating Design Assurance Levels (DAL A–E per ARP 4754A) to each element, which cascades to derived requirements and verification activities
- Safety assessment scope — Defining which functions, failure modes, and design characteristics are analyzed within each FMEA, FHA, or PSSA document
Entity Hierarchy
System Elements follow a 5-level decomposition hierarchy from top-level product to lowest-level replaceable unit:
| Level | Element Type | Example | DAL | Documents |
|---|---|---|---|---|
| System | System | Flight Control Computer (FCC) | B | System SFMEA, FHA, PSSA, SSA |
| Subsystem | Subsystem | Sensor Interface Module | B | Subsystem SFMEA, Subsystem Reqs |
| Assembly | Assembly | Sensor Interface Board Assembly | B | Design Reqs |
| Subassembly | Subassembly | Connector Module | C | Component DFMEA |
| Component | Component | Air Data Computer Interface (ADCI) | C | Component DFMEA, Component Reqs |
Custom Fields
System Elements carry two primary custom fields for architecture and safety classification:elementType (Enumeration)
| Value | Description | Typical Use |
|---|---|---|
| System | Top-level product or system | Flight Control Computer (FCC) — root of decomposition tree. Hosts system-level SFMEA and FHA documents. |
| Subsystem | Major functional group within a system | Sensor Interface Module, Processing Core Module. Each subsystem has its own subsystem requirements spec and subsystem SFMEA. |
| Assembly | Physical grouping of smaller subassemblies or components | Sensor Interface Board Assembly. May contain design requirements. |
| Subassembly | Intermediate decomposition level | Connector Module, power distribution subassembly. Bridge between assembly and component levels. |
| Component | Lowest-level replaceable unit (LRU) | Air Data Computer Interface (ADCI), Main Flight Processor. Each component has a component-level design requirements spec and DFMEA. |
elementType to build the hierarchical tree view. SFMEA documents are typically created at the Subsystem level; DFMEA documents at the Component level.
dal (Design Assurance Level)
| Value | Standard | Description | Scope |
|---|---|---|---|
| A | ARP 4754A, DO-178C, DO-254 | Catastrophic failure condition — most stringent certification activities | Full rigor: requirements decomposition, design V&V, process assurance, configuration management |
| B | ARP 4754A, DO-178C, DO-254 | Hazardous failure condition — substantial certification rigor | Design requirements, verification, configuration control, but relaxed process rigor vs DAL A |
| C | ARP 4754A, DO-178C, DO-254 | Major failure condition — moderate assurance | Design documentation, basic verification, configuration identification |
| D | ARP 4754A, DO-178C, DO-254 | Minor failure condition — minimal assurance | Minimal design documentation and verification |
| E | ARP 4754A, DO-178C, DO-254 | No safety effect — no specific certification activities | Standard engineering practices; no safety-driven constraints |
- Complete requirements decomposition (customer → system → subsystem → design level)
- All design requirements verified by test
- All failure modes scored and mitigated if RPN exceeds thresholds
- Configuration management with formal change control
The exact mapping between DAL level and certification activities (e.g., which DO-178C objectives apply to DAL C vs DAL D) is configurable per project via the Compliance Matrix risksheet. Review your project’s compliance configuration to confirm DAL-to-objective alignment.
System Element Status Lifecycle
System Elements follow a 7-state lifecycle workflow identical to the default work item workflow:| Status | Color | Meaning |
|---|---|---|
| Draft | Blue (#3366FF) | Element is under initial creation; not yet reviewed |
| In Progress | Blue-gray | Element is being refined or updated |
| In Review | Light Yellow (#FFFF99) | Element awaiting approval; under formal review |
| Pending Approval | Yellow (#FFFF33) | Element ready for signature; awaiting lead approval |
| Approved | Green (#66FF66) | Element formally approved; locked from casual edit |
| Rejected | Red (#FF3300) | Element was rejected during review; rework required |
| Obsolete | Gray | Element has been superseded or removed from active design |
Relationships and Traceability
System Elements are the anchor points for traceability across multiple analysis viewpoints:
Key Link Roles
| Link Role | Direction | From | To | Purpose |
|---|---|---|---|---|
| isDecomposedInto | Parent → Child | System Element | System Element | Hierarchical decomposition (System → Subsystem → Component) |
| hasFunction | Element → Function | System Element | Function | Functions analyzed in SFMEA scope for this element |
| hasCharacteristic | Element → Characteristic | System Element | Characteristic | Design characteristics assessed in DFMEA scope for this element |
| isDefinedIn | Requirement → Element | Design Requirement | System Element | Design req applies to this system element |
| isPresentIn | Failure Mode → Element | Failure Mode | System Element | Failure mode can occur in this element (SFMEA/DFMEA scope) |
| affects | Failure Cond → Element | Failure Condition | System Element | Failure condition impacts this element (FHA/PSSA scope) |
| mitigates | Control → Element | Risk Control | System Element | Control reduces risk in this element (Risk Control Plan scope) |
| isTestedBy | Requirement → Test | Design Requirement | Test Case | Test case verifies design requirement for this element |
- SFMEA/DFMEA scope definition — All functions and characteristics linked to a system element are candidates for FMEA analysis at that level
- Requirements traceability — Design requirements linked to a component are verified by test cases and must satisfy parent system/subsystem requirements
- Safety assessment coverage — Failure conditions affecting a system element are analyzed in FHA documents scoped to that element; mitigations linked via Risk Controls
System Element in PowerSheet Views
PowerSheets reference system elements through multiple mechanisms:System Structure Navigator (Dashboard)
The System Structure Navigator is a role dashboard that renders an interactive tree view of all system elements, grouped byelementType. Users click on an element to expand its children and view associated documents (requirements specs, FMEA documents, etc.).
Component RTM PowerSheet
The Component RTM PowerSheet scopes the requirements traceability matrix to a single system element (component). Its row source constrains to:- System requirements linked to the component
- Design requirements specific to that component
- Characteristics and test cases for component-level verification
Design Characteristics & Functions PowerSheets
Separate PowerSheets are created for each subsystem showing:- Subsystem - Functions — All functions assigned to that subsystem (via
hasFunctionlink) - Component - Design Characteristics — All characteristics assigned to that component (via
hasCharacteristiclink)
System Element Document Types
Different document types in your project are typically constrained to specific system element levels:| Document Type | Typical Level | Constraint | Example |
|---|---|---|---|
| System Requirements Specification | System | Scoped to the top-level system element | FCC System Requirements Specification |
| Subsystem Requirements Specification | Subsystem | Scoped to a specific subsystem element | Sensor Interface Module Subsystem Requirements |
| Component Requirements Specification | Component | Scoped to a component element | ADCI Component Requirements Specification |
| System SFMEA | System/Subsystem | Analyzes functions at system or subsystem level | FCC System SFMEA |
| Component DFMEA | Component | Analyzes components and their design characteristics | ADCI Component DFMEA |
| Fault Tree Analysis | System | Top-level undesired state analysis | FCC Functional Hazard (Top Event) FTA |
| Safety Assessment (PSSA/SSA) | System/Subsystem | Combines FHA, SFMEA, DFMEA into safety argument | FCC Preliminary System Safety Assessment |
Creating and Organizing System Elements
System elements are typically created early in the project to establish the architectural decomposition. You organize them hierarchically:- Create the top-level System element (e.g., “Flight Control Computer”)
- For each major functional group, create a Subsystem element (e.g., “Sensor Interface Module”)
- For each Subsystem, create Assembly or Component elements as appropriate
- Assign DAL to each element based on the failure condition severities identified in your FHA
- Link requirements, functions, and characteristics to the appropriate elements so PowerSheets and risksheets can scope their content
isDecomposedInto relationship.
Sources
Source: RTM Domain Model (.polarion/nextedy/models/rtm.yaml)SystemElement entity type, hierarchical decomposition, DAL classification, links to functions, characteristics, failure modes, and risk controls. Source: System Element Custom Fields (
.polarion/tracker/fields/systemElement-custom-fields.xml)elementType enumeration (System, Subsystem, Assembly, Subassembly, Component) and dal enumeration (A, B, C, D, E). Source: System Element Workflow (
.polarion/tracker/workflow/systemElement-workflow.xml)7-state lifecycle workflow (Draft, In Progress, In Review, Pending Approval, Approved, Rejected, Obsolete). Source: PowerSheet Configurations (
.polarion/nextedy/sheet-configurations/system-elements.yaml and related)System Element PowerSheet views, System Structure Navigator dashboard, Component RTM scoping. Source: UI Walkthrough (
datasets/sol-aero-ui-walkthrough/summary.md)Aero1 project architecture showing FCC decomposition into subsystems and components with DAL assignments.
Source References (dev)
Source References (dev)
Code:
.polarion/nextedy/models/rtm.yaml (0.65) · .polarion/tracker/fields/systemElementType-enum.xml, systemElement-status-enum.xml (0.64) · .polarion/pages/scripts/velocity/nextedy_solutions.vm (0.59) · .polarion/tracker/fields/testCase-custom-fields.xml, desReq-custom-fields.xml, processStep-custom-fields.xml, characteristic-custom-fields.xml, systemElement-custom-fields.xml, commonCauseEvent-custom-fields.xml, riskControl-custom-fields.xml, task-custom-fields.xml, custom-fields.xml (0.58) · .polarion/tracker/workflow/systemElement-workflow.xml (0.58) · .polarion/nextedy/sheet-configurations/DO-160G Environmental Qualification.yaml, Component RTM.yaml, Configuration Index.yaml, Design Verification Sheet.yaml, Interface Control Matrix.yaml, Problem Report Tracker.yaml, Process Steps.yaml, Review Action Item Tracker.yaml, SOI Stage Gate Dashboard.yaml, Use Steps Specification.yaml, User Need Validation Sheet.yaml, characteristics.yaml, component-characteristics.yaml, customer-requirements.yaml, design-requirements.yaml, subsystem-functions.yaml, subsystem-verification.yaml, system-elements.yaml, test-verification.yaml (0.55) · .polarion/pages/spaces/_default/Data Model/attachments/diagram_1771111587_documents.mxg.svg, diagram_1771111587_risk.mxg.svg, diagram_1771111587_traceability.mxg.svg, modules/Requirements/SYSTEM-ELEMENTS/attachments/diagram_20260215-0024.44000.mxg.svg (0.52) · .polarion/pages/spaces/_default/Requirements Traceability Summary/page.xml, Verification Validation Summary/page.xml, Risk Control Effectiveness Report/page.xml, System Decomposition Report/page.xml, FMEA Coverage Report/page.xml, Classification Consistency Report/page.xml, System FMEA Report/page.xml, System Structure Navigator/page.xml (0.52) · .polarion/pages/spaces/_default/Data Model/page.xml (0.51) · modules/Risks/COMPLIANCE-001/module.xml, modules/Risks/MIL-STD-882E-HTS-001/module.xml, modules/Risks/SEC-THREAT-001/module.xml, modules/Risks/SFMEA-SUB-001/module.xml, modules/Risks/SFMEA-SUB-002/module.xml, modules/Risks/SFMEA-SUB-003/module.xml (0.50)