Link Cardinality - Nextedy Documentation

Why Cardinality Matters

Siemens Polarion ALM allows any work item to link to any number of other work items through link roles. This open-ended flexibility means Polarion itself does not enforce limits like “a hazard must link to at least one risk control” or “a system requirement should derive from exactly one user need.” Powersheet’s data model introduces cardinality as a semantic layer on top of Polarion’s link roles. Think of it like database schema design: just as a relational database enforces foreign key constraints, Powersheet’s cardinality settings enforce relationship multiplicity in the user interface.

Cardinality Options

The cardinality property on a relationship definition accepts the following supported values:

Cardinality	From Side	To Side	Typical Use Case
`many-to-one`	Multiple	Single	Many design reqs derive from one system req
`one-to-many`	Single	Multiple	One user need decomposes into many system reqs
`many-to-many`	Multiple	Multiple	Hazards linked to multiple risk controls and vice versa

Although one-to-one appears conceptually in the diagram above, it is not a supported cardinality value in the current Powersheet data model. Use many-to-one when you need a single-valued reference on the “from” side, or model uniqueness through validation rather than cardinality.

How Cardinality Is Defined

Cardinality is set on each relationship in the relationships array of the data model YAML:

relationships:
  - from: UserNeed
    to: SystemRequirement
    cardinality: one-to-many
    storage: linkedWorkItems
    linkRole: refines
    direct: systemRequirements
    back: userNeed

In this example, one UserNeed can link to many SystemRequirement items (one-to-many). The direct becomes a collection-valued property on UserNeed, while back becomes a single-valued property on SystemRequirement.

Impact on the User Interface

Cardinality directly controls the sheet’s editing behavior:

Single-value relationships (the “one” side) display a single-select picker. The user can choose exactly one target entity.
Multi-value relationships (the “many” side) display a multi-select picker. The user can select multiple related entities.

A many-to-one relationship means the “from” entity can reference exactly one “to” entity, but the “to” entity can be referenced by many “from” entities. The navigation property on the “from” side is single-valued; the navigation property on the “to” side (via back) is collection-valued.

Cardinality and Polarion Link Roles

Polarion link roles are inherently many-to-many — any work item can create any number of links using a given role. Powersheet’s cardinality setting does not change this at the Polarion level; instead, it enforces the constraint at the UI and validation level within the sheet. This means:

If a relationship is defined as many-to-one, the sheet will present a single-value picker and prevent users from creating additional links through the powersheet
Links created outside Powersheet (via Polarion’s native UI) are not retroactively constrained

The exact enforcement behavior for cardinality violations (whether existing extra links are hidden or shown with a warning) may vary. Test with your configuration to confirm.

Common RTM Cardinality Pattern

A typical Requirements Traceability Matrix uses the following cardinality chain:

From	To	Cardinality	Link Role
`UserNeed`	`SystemRequirement`	`one-to-many`	`refines`
`SystemRequirement`	`DesignRequirement`	`one-to-many`	`refines`
`Hazard`	`RiskControl`	`many-to-many`	`mitigates`

This creates a hierarchy where each upstream requirement can decompose into multiple downstream items, while hazard-to-control relationships remain flexible.

Entity Types and Relationships — How entity types and relationships are structured
Process Constraints — Additional rules for loading, creating, and picking entities
Creating Your First Data Model — Hands-on tutorial for setting up cardinality

​Why Cardinality Matters

​Cardinality Options

​How Cardinality Is Defined

​Impact on the User Interface

​Cardinality and Polarion Link Roles

​Common RTM Cardinality Pattern

​Related Pages

Why Cardinality Matters

Cardinality Options

How Cardinality Is Defined

Impact on the User Interface

Cardinality and Polarion Link Roles

Common RTM Cardinality Pattern

Related Pages