Cardinality - Nextedy Documentation

Cardinality is a Powersheet domain model concept. Polarion link roles do not have a cardinality setting — Powersheet uses the cardinality value to control how the sheet renders and navigates relationship data.

Cardinality Property

Name	Type	Default	Description
`cardinality`	`string`	None (required)	Defines the relationship multiplicity between the `from` and `to` entity types

The cardinality property is declared within each entry of the relationships array in the domain model YAML. It works together with from, to, storage, linkRole, direct, and back to form a complete relationship definition.

Supported Cardinality Values

Value	From Side	To Side	Description
`one-to-one`	Single entity	Single entity	Each source entity links to exactly one target entity
`one-to-many`	Single entity	Multiple entities	Each source entity links to multiple target entities
`many-to-one`	Multiple entities	Single entity	Multiple source entities link to one target entity
`many-to-many`	Multiple entities	Multiple entities	Multiple source entities link to multiple target entities

How the Three Configuration Layers Connect

The domain model, sheet sources, and sheet columns are connected through navigation property names. The cardinality of a relationship determines which expand pattern and column binding syntax to use.

Domain model defines entity types and relationships (including cardinality, direct, and back navigation property names)
Sheet sources define how to query and expand those relationships using the navigation property names
Sheet columns define how to display the resulting data using binding paths derived from the same navigation property names

Shared Domain Model for Examples

All examples on this page use the following minimal domain model:

domainModelTypes:
  Chapter:
    polarionType: heading

  UserNeed:
    polarionType: user_need
    properties:
      description:
      severity:

  SystemRequirement:
    polarionType: sys_req
    properties:
      description:
      severity:

  DesignRequirement:
    polarionType: des_req
    properties:
      description:

relationships:
  - from: UserNeed
    to: Chapter
    cardinality: many-to-one
    storage: linkedWorkItems
    linkRole: parent
    direct:
      name: chapter
    back:
      name: userNeeds

  - from: SystemRequirement
    to: UserNeed
    cardinality: many-to-many
    storage: linkedWorkItems
    linkRole: decomposes
    direct:
      name: userNeeds
    back:
      name: systemRequirements

Many-to-One (N:1)

Scenario: Each UserNeed belongs to exactly one Chapter. The relationship uses the direct direction with name: chapter (singular, scalar navigation property). Because the cardinality is many-to-one, the navigation property on the “from” side points to a single entity.

Relationship Definition

- from: UserNeed
  to: Chapter
  cardinality: many-to-one
  storage: linkedWorkItems
  linkRole: parent
  direct:
    name: chapter
  back:
    name: userNeeds

Source Configuration

sources:
  - id: user_needs
    query:
      from: UserNeed
    expand:
      - name: chapter

The expand uses the direct navigation property name chapter. Because it is a scalar property (N:1), the expand resolves to a single related entity per row.

Column Configuration

columns:
  title:
    title: Title
    hasFocus: true
  chapter:
    title: Chapter
    display: title
    list:
      search:
        - title
  chapter.title:
    title: Chapter Title
    isReadOnly: true

Column Key	Behavior	Description
`chapter`	Single-value reference picker	Scalar navigation property renders as a dropdown picker. The `display` property controls the displayed label. The `list.search` array defines searchable fields.
`chapter.title`	Read-only display	Dot-notation accesses a property on the referenced entity. Set `isReadOnly: true` to prevent editing.

A singular navigation property name (e.g., chapter) indicates a N:1 cardinality. The sheet renders this as a single-value reference picker, not an expandable child level.

One-to-Many (1:N)

Scenario: Each Chapter has multiple child UserNeed items. This is the reverse side of the many-to-one relationship above. It uses the back direction with name: userNeeds (plural, collection navigation property).

Relationship Definition

The same relationship entry is used — the 1:N perspective is simply the back direction of the N:1 relationship:

- from: UserNeed
  to: Chapter
  cardinality: many-to-one
  storage: linkedWorkItems
  linkRole: parent
  direct:
    name: chapter
  back:
    name: userNeeds

When querying from Chapter, the back.name value userNeeds provides the collection navigation property.

Source Configuration

sources:
  - id: chapters
    query:
      from: Chapter
    expand:
      - name: userNeeds

The expand uses the back navigation property name userNeeds. Because it is a collection property (1:N), the expand creates child rows underneath each Chapter.

Column Configuration

columns:
  title:
    title: Chapter
    hasFocus: true
  userNeeds:
    title: Title
    hasFocus: true

Column Key	Behavior	Description
`userNeeds`	Child row expansion	Collection navigation property expands into a new hierarchical level in the sheet. Each child row displays one `UserNeed`.

When a collection navigation property is used as a column key, it opens a new sheet level with child rows. No dot-notation is needed — the expand directly opens the child level.

Many-to-Many (M:N)

Scenario: UserNeed items are linked to multiple SystemRequirement items, and vice versa. Many-to-many relationships use an association entity as an intermediate layer. The source expand is two levels deep, and column binding uses dot-notation to reach through the association to the target entity.

Relationship Definition

- from: SystemRequirement
  to: UserNeed
  cardinality: many-to-many
  storage: linkedWorkItems
  linkRole: decomposes
  direct:
    name: userNeeds
  back:
    name: systemRequirements

Source Configuration

sources:
  - id: user_needs
    query:
      from: UserNeed
    expand:
      - name: systemRequirements
        expand:
          - name: systemRequirement

The expand is two levels:

systemRequirements — navigates to the association entity (collection)
systemRequirement — navigates from the association to the actual target entity (scalar)

Column Configuration

columns:
  title:
    title: Title
    hasFocus: true
  systemRequirements.systemRequirement:
    title: System Requirement
    list:
      search:
        - objectId
        - title
      createNew: true
  systemRequirements.systemRequirement.title:
    title: SysReq Title
    hasFocus: true

Column Key	Behavior	Description
`systemRequirements.systemRequirement`	Multi-item reference picker	Two-level dot-notation traverses association then target. Renders as a multi-item picker. `list.search` enables search; `createNew: true` allows creating new linked items.
`systemRequirements.systemRequirement.title`	Display field on target	Three-level dot-notation accesses a property on the target entity through the association.

M:N relationships always require a two-level expand in the source configuration. If you omit the inner expand (- name: systemRequirement), the column will bind to the association entity rather than the target entity, and data will not display correctly.

One-to-One (1:1)

The one-to-one cardinality value means each entity on both sides links to exactly one entity on the other side. The behavior is identical to many-to-one from a source expand and column binding perspective — the navigation property is scalar, and the column renders as a single-value reference picker.

- from: DesignRequirement
  to: SystemRequirement
  cardinality: one-to-one
  storage: linkedWorkItems
  linkRole: derives_from
  direct:
    name: systemRequirement
  back:
    name: designRequirement

The direct.name is singular (systemRequirement), and the column key systemRequirement behaves the same as in a N:1 relationship. The navigation property names declared in direct and back follow consistent naming conventions that signal the cardinality:

Direction	Cardinality Side	Naming Convention	Example
`direct`	N:1 (scalar)	Singular, camelCase	`chapter`, `systemRequirement`
`direct`	M:N (collection)	Plural, camelCase	`userNeeds`, `riskControls`
`back`	1:N (collection)	Plural, camelCase	`userNeeds`, `designRequirements`
`back`	M:N (collection)	Plural, camelCase	`systemRequirements`, `hazards`

Singular navigation property names (e.g., chapter) indicate scalar references (N:1 or 1:1). Plural names (e.g., userNeeds) indicate collections (1:N or M:N). Consistent naming makes sheet configurations easier to read and debug.

Relationship Context Properties

Each relationship entry that includes a cardinality value also requires the following sibling properties:

Property	Type	Required	Description
`from`	`string`	Yes	Source entity type name. Must match a key in `domainModelTypes`.
`to`	`string`	Yes	Target entity type name. Must match a key in `domainModelTypes`.
`cardinality`	`string`	Yes	One of: `one-to-one`, `one-to-many`, `many-to-one`, `many-to-many`.
`storage`	`string`	Yes	Storage mechanism. Typically `linkedWorkItems` for Polarion link-based relationships.
`linkRole`	`string`	Yes	Polarion link role identifier (e.g., `parent`, `refines`, `decomposes`, `mitigates`).
`direct`	`object`	Yes	Forward navigation direction. Contains `name` (the navigation property name from `from` to `to`).
`back`	`object`	Yes	Reverse navigation direction. Contains `name` (the navigation property name from `to` back to `from`).

The direct and back objects each contain a name property that defines the navigation property used in source expands and column binding paths.

Cardinality Summary

Cardinality	Model	Source Expand	Column Binding	UI Behavior
N:1	`cardinality: many-to-one`, `direct.name: chapter`	`- name: chapter`	`chapter`, `chapter.title`	Single-value reference picker
1:N	Reverse of N:1, `back.name: userNeeds`	`- name: userNeeds`	`userNeeds`	Child rows (new sheet level)
M:N	`cardinality: many-to-many`, `back.name: systemRequirements`	`- name: systemRequirements` then `- name: systemRequirement`	`systemRequirements.systemRequirement`	Multi-item reference picker
1:1	`cardinality: one-to-one`, `direct.name: systemRequirement`	`- name: systemRequirement`	`systemRequirement`, `systemRequirement.title`	Single-value reference picker

Complete YAML Example

A full domain model demonstrating all cardinality patterns with the standard RTM entity set:

domainModelTypes:
  UserNeed:
    polarionType: user_need
    properties:
      description:
      severity:

  SystemRequirement:
    polarionType: sys_req
    properties:
      description:
      severity:

  DesignRequirement:
    polarionType: des_req
    properties:
      description:

  Hazard:
    polarionType: hazard
    properties:
      description:

  RiskControl:
    polarionType: risk_control
    properties:
      description:

relationships:
  # N:1 — each SystemRequirement derives from one UserNeed
  - from: SystemRequirement
    to: UserNeed
    cardinality: many-to-one
    storage: linkedWorkItems
    linkRole: refines
    direct:
      name: userNeed
    back:
      name: systemRequirements

  # 1:N — each UserNeed has many SystemRequirements (reverse of above)
  # No separate entry needed; use the back direction of the N:1 above.

  # 1:1 — each DesignRequirement derives from one SystemRequirement
  - from: DesignRequirement
    to: SystemRequirement
    cardinality: one-to-one
    storage: linkedWorkItems
    linkRole: derives_from
    direct:
      name: systemRequirement
    back:
      name: designRequirement

  # M:N — Hazards linked to multiple RiskControls and vice versa
  - from: Hazard
    to: RiskControl
    cardinality: many-to-many
    storage: linkedWorkItems
    linkRole: mitigates
    direct:
      name: riskControls
    back:
      name: hazards

Relationships — Full relationship definition reference
Navigation Directions — Direct and back direction details
Link Roles — Polarion link role configuration
Domain Model Types — Entity type definitions
Binding Syntax — Column binding path syntax
Multi-Item Columns — Configuring columns for M:N relationships
Sources — Sheet source and expand configuration
Expand Clause — Query expand clause reference

Sources

Source Code

Relationship.java
DomainModelV2.java
DatabridgeConstants.java
DomainModelTypeV2.java

​Cardinality Property

​Supported Cardinality Values

​How the Three Configuration Layers Connect

​Shared Domain Model for Examples

​Many-to-One (N:1)

​Relationship Definition

​Source Configuration

​Column Configuration

​One-to-Many (1:N)

​Relationship Definition

​Source Configuration

​Column Configuration

​Many-to-Many (M:N)

​Relationship Definition

​Source Configuration

​Column Configuration

​One-to-One (1:1)

​Navigation Property Naming Conventions

​Relationship Context Properties

​Cardinality Summary

​Complete YAML Example

​Related Pages

Cardinality Property

Supported Cardinality Values

How the Three Configuration Layers Connect

Shared Domain Model for Examples

Many-to-One (N:1)

Relationship Definition

Source Configuration

Column Configuration

One-to-Many (1:N)

Relationship Definition

Source Configuration

Column Configuration

Many-to-Many (M:N)

Relationship Definition

Source Configuration

Column Configuration

One-to-One (1:1)

Navigation Property Naming Conventions

Relationship Context Properties

Cardinality Summary

Complete YAML Example

Related Pages