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How to Categorise Relationships | Is-A, Part-Of, Causes, Uses, Owns, Supports and More

Relationships explain how one thing connects to another.

A dolphin is-a mammal. A battery is part-of a phone. A teacher teaches a student. A company owns a subsidiary. A storm can cause flooding. A source can support a claim. These are not interchangeable links.

Quick answer: how should relationships be categorised?

  • Type: is-a, part-of, located-in, causes, uses, owns, supports, precedes?
  • Direction: does A relate to B differently from B to A?
  • Symmetry: if A relates to B, must B relate to A?
  • Transitivity: if A relates to B and B to C, does A relate to C?
  • Cardinality: one-to-one, one-to-many, many-to-many?
  • Time: when is the relationship valid?
  • Context: under which role, jurisdiction or system?
  • Evidence: what supports the link?
  • Confidence: certain, probable, disputed?
  • Provenance: where did the relation assertion come from?

This article complements How Classification by Relationships Works. That page explains how relationships can help classify entities; this page classifies the relationship types themselves.

1. Start with the relation, not the connected things

Two identical entity types can participate in very different relationships. Person-to-person can mean parent-of, teaches, employs, advises or knows.

2. Is-a expresses type membership

“A whale is a mammal” connects a narrower class to a broader class.

3. Instance-of differs from is-a

“This whale is an instance of bottlenose whale” connects an individual to a class; is-a usually connects classes.

4. Part-of expresses composition

A wheel is part of a bicycle. It is not a kind of bicycle.

5. Contains is the inverse of part-of

Store inverse relations explicitly or derive them consistently.

6. Located-in expresses spatial containment

A school is located in Singapore; this is not the same as being part of the Singapore government.

7. Adjacent-to expresses proximity

Neighbouring places may be adjacent without one containing the other.

8. Connected-to expresses network linkage

Two stations may be connected even when far apart geographically.

9. Causes is stronger than precedes

Earlier events do not automatically cause later events.

10. Contributes-to represents partial causation

Complex outcomes often have several contributing causes rather than one sufficient cause.

11. Enables differs from causes

A condition can make an event possible without producing it directly.

12. Prevents and inhibits are negative causal relations

They describe reduced probability or blocked transition rather than positive production.

13. Uses connects agent to resource or tool

A process uses energy; a student uses a calculator; a machine uses software.

14. Produces connects process to output

Production should be separated from ownership and possession.

15. Owns is a legal or institutional relation

Ownership differs from control, custody and possession.

16. Controls describes operational power

An entity may control an asset without owning it.

17. Member-of expresses institutional belonging

Membership differs from employment and ownership.

18. Employs and works-for are inverses

Typed inverses make role direction clear.

19. Authored-by connects artefact to creator

Creator, editor, publisher and custodian are different relationships.

20. Supports connects evidence to claim

Support strength and independence should remain separate properties.

21. Contradicts connects competing claims

Contradiction is stronger than mere difference.

22. Resembles expresses similarity

Similarity is usually symmetric, but the degree and feature space matter.

23. Precedes and follows express order

Temporal ordering should not be confused with causation.

24. Depends-on expresses requirement

A downstream task can depend on an upstream approval or resource.

25. Directionality matters

Parent-of is directional; sibling-of is typically symmetric.

26. Symmetry should be explicit

If A is adjacent to B, B is normally adjacent to A. If A owns B, B does not own A.

27. Transitivity should be explicit

Some broader-narrower and containment relations may transit; friendship usually should not.

28. Cardinality constrains structure

A person can have many memberships; a record may have one canonical owner under a particular governance model.

29. Time makes relationships dynamic

Employment, ownership, membership and location can begin and end.

30. Context changes relationship validity

A person can supervise another in one project but not in the wider organisation.

31. Provenance belongs to relationship assertions

Record which source claims that one entity owns, causes or supports another.

32. Confidence can attach to the edge

The entities may be certain while the relation between them remains disputed.

33. Generic “related-to” should be a last resort

Untyped links lose meaning and make reasoning difficult.

34. Relation taxonomies need governance

Duplicate relation names, ambiguous inverses and inconsistent direction create graph failure.

35. AI can extract relationship candidates

Models can infer likely edges from text, but inferred relations should preserve evidence and confidence.

36. Relationship extraction can confuse correlation with causation

Use conservative relation types where evidence does not justify a stronger edge.

37. A practical relationship record

  • relationship ID;
  • subject ID;
  • relation type;
  • object ID;
  • direction;
  • inverse relation;
  • symmetry;
  • transitivity;
  • cardinality;
  • valid time;
  • context;
  • evidence;
  • confidence;
  • provenance;
  • version.

38. Relationship categories should enable reasoning

Good relation types let people and machines traverse knowledge without inventing meaning at every step.

39. Relations are not decoration

They often carry the structure that turns isolated records into a knowledge system.

40. The deeper idea

Categories tell us what things are. Relationships tell us what things mean together.

To categorise a relationship well is to preserve what connects two things, in which direction, under what conditions, and with what evidence.

Final answer

Categorise relationships by relation type, direction, symmetry, transitivity, cardinality, time, context, evidence, confidence and provenance. Keep is-a separate from part-of, sequence separate from causation, ownership separate from control, and use typed relations wherever possible instead of generic “related-to”.

Continue through the series

Explore the connected learning guides

Choose the question that brought you here. Open one useful guide, try a small task, and stop when you have what you need.

Take one question further

The same learning habit can travel across subjects, while each subject keeps its own methods. These routes help you notice a difficulty, understand one part of it, and return to something you can do.

A word is familiar, but using it is difficult.

Move from recognising a word to retrieving it in a new context. Understand vocabulary plateaus.

Try it without the guide: Choose one word you already know. Close the guide and use it in a new sentence. Explain why it fits; try another context tomorrow.

A piece of writing has ideas, but the reader loses the thread.

Make the order of events and the links between sentences clear. Explore composition writing.

Try it without the guide: Choose one short paragraph. Read the relevant explanation, close it, and revise the paragraph. Ask someone to tell you what happened and why.

The Mathematics seems familiar, but marks still disappear.

Find the first point where the working stops being reliable. Find Secondary 4 A-Math mark leakage.

Try it without the guide: For a Secondary 4 A-Math question you have attempted, locate the first uncertain line. Repair that step, then try a comparable question without the worked answer.

A Science fact is remembered, but the explanation is incomplete.

Connect the evidence to a scientific idea and the resulting change. Follow the Primary Science learning route.

Try it without the guide: Choose a familiar Primary Science example. Explain the evidence, the idea and the result without notes. Then change one condition and explain your prediction.

Two accounts of the world seem to disagree.

Check the question, source, date and evidence before combining claims. Explore the World Knowledge research library.

Try it without the guide: Take one claim. Find the source best placed to support it, note its date, and state what remains uncertain. Return to your original question.

There is plenty of help, but independence is hard to see.

Check what the learner can understand and do after support is removed. Understand how education works.

Try it without the guide: Choose one small task the child has practised. Agree on a calm, brief attempt without prompts. Use what happens to choose one next step, then stop.

For the structure behind these connections, read the eduKateSingapore runtime manifest and the eduKate ecosystem boot contract. The reader map describes public navigation; those manifests preserve the wider ownership and return rules.