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Implied Relations

Implied relations are Trail's killer feature. Define a rule once, and Trail automatically creates bidirectional links without you having to add them manually.

The Problem

Without implied relations, bidirectional linking requires double work:

In Parent.md: 

down::[[Child]]

In Child.md: 

up::[[Parent]]

If you forget one, your graph has gaps.

The Solution

With an implied relation, you link once:

In Child.md: 

up::[[Parent]]

Trail automatically infers that Parent -down-> Child exists. You see it in the Trail pane without adding any link to Parent.md.

Configuring Implied Relations

  1. Open Settings → Trail
  2. Expand the relation you want to add implications to
  3. In Implied relations, click Add implied relation
  4. Select the target relation and direction

Direction Types

Forward

Creates the implied relation in the same direction as the source.

Source: A -up-> B
Rule:   up → parent (forward)
Result: A -parent-> B

Use case: Creating aliases. If up implies parent forward, both mean the same thing.

Reverse

Creates the implied relation in the opposite direction.

Source: A -up-> B
Rule:   up → down (reverse)
Result: B -down-> A

Use case: Bidirectional hierarchies. Every up link automatically creates a down link going back.

Both

Creates implied relations in both directions.

Source: A -up-> B
Rules:  up → parent (both)
Result: A -parent-> B AND B -parent-> A

Use case: Symmetric relationships like "related-to" or "sibling".

Default Implied Relations

Trail's default configuration includes these rules:

Source Target Direction Meaning
up down Reverse If A is up from B, B is down from A
down up Reverse If A is down from B, B is up from A
next prev Reverse If A is next after B, B is prev before A
prev next Reverse If A is prev before B, B is next after A

Practical Examples

Family Tree

Relations:

  • parent (ascending)
  • child (descending)

Implied rules:

  • parent → child (reverse)
  • child → parent (reverse)

In Alice.md: 

parent::[[Bob]]

Result: Bob's Trail pane shows child: Alice automatically.

Citation Network

Relations:

  • cites (descending)
  • cited-by (descending)

Implied rules:

  • cites → cited-by (reverse)

In Paper A.md: 

cites::[[Paper B]]
cites::[[Paper C]]

Result: Paper B and Paper C both show cited-by: Paper A in their Trail panes.

Sequential Content

Relations:

  • next (sequential)
  • prev (sequential)

Implied rules:

  • next → prev (reverse)
  • prev → next (reverse)

In Chapter 1.md: 

next::[[Chapter 2]]

Result: Chapter 2's Trail pane shows prev: Chapter 1.

Symmetric Relationships

Relations:

  • related (descending)

Implied rules:

  • related → related (reverse)

In Topic A.md: 

related::[[Topic B]]

Result: Topic B shows related: Topic A. The relationship is symmetric—adding it once links both ways with the same relation type.

Implied vs Explicit

In the Trail pane, implied relations appear slightly muted compared to explicit ones. This helps you distinguish:

  • Explicit: You added this link directly
  • Implied: Trail inferred this from a rule

Both are fully functional for navigation and traversal.

See Implied vs Explicit for more details.

Chain Implications

Implied relations can chain through multiple levels.

Example:

  • A -up-> B (explicit)
  • Rule: up → down (reverse)
  • Result: B -down-> A (implied)

If you have another rule:

  • Rule: down → contains (forward)
  • Result: B -contains-> A (implied from implied)

Trail computes the full transitive closure of implications.

Best Practices

Always Set Up Reverse Relations

For any hierarchical relation, define the reverse:

parent → child (reverse)
child → parent (reverse)

This ensures your graph is complete from any entry point.

Use Forward for Aliases

If you want multiple names for the same concept:

up → parent (forward)
up → ancestor (forward)

Now up, parent, and ancestor all create the same connections.

Be Careful with Both

The both direction creates symmetric relationships. Only use it when the relationship truly works both ways (like "related-to" or "sibling").

Don't use both for hierarchical relations—parent (both) would make every parent also a child of their children.

Troubleshooting

Implied Relations Not Appearing

  1. Check the rule exists: Open the source relation's settings and verify the implied relation is configured
  2. Check direction: Forward vs reverse makes a big difference
  3. Check relation names: The target relation must exist
  4. Refresh: Open the Trail pane's menu and click Refresh

Too Many Implied Relations

If your Trail pane is cluttered:

  1. Review your implied rules for unintended chains
  2. Use the filter menu to hide specific relation types
  3. Consider whether you need all the implications you've defined