Lesson 3 of 6 in this unit
Help specialists understand each other.
Compare prose, structured records, and vectors; diagnose lost information and mismatched coordinate meanings.
By the end: Choose interfaces that preserve task-relevant information, distinguish modular systems from internal experts, and combine events with explicit structure.
Prerequisites and path options
Why learn this? Prevent errors when components exchange units, coordinates or representations.
Start with something concrete.
One teammate says “the cup is on the right.” Another needs its exact position to pick it up. Both may understand their own task well, while their shared message is too vague to connect them.
Try the interactive modelTwo components both use vectors with two numbers. Can they necessarily exchange these vectors directly?
Change one thing. Watch what follows.
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Understand what changed.
A shorter explanation, with the original worked examples available below. Both explain the same experiment and its limits.
The idea in everyday terms
Two components can each work correctly yet fail when connected. A position in centimetres is a different input from the same number in metres. Swapping coordinate order can also change the intended location.
What to watch in the experiment
An interface is an agreement about what a message means. Inspect the sender’s output and the receiver’s assumptions, then apply the explicit conversion between them. Compare message formats and the timing of dependent work.
What this does not establish
The observations and conversions here are programmed. Meeting a position tolerance does not prove that a real grasp is safe or that arbitrary language or image representations can be exchanged.
Open the full worked examples, calculations and limitations
This is the same reference used in Technical mode. Expand it whenever you need the exact numbers, assumptions or further explanation.
A good specialist can still be a bad teammate
A vision component might locate objects accurately while a controller moves accurately to numerical coordinates. Connecting them can still fail if one uses centimetres and the other expects metres, or if they disagree about the coordinate frame. The interface is part of the system’s behavior.
The cup lab uses exact programmed observations so you can isolate this boundary. It does not run image recognition, learn a latent representation, or control hardware. Its position tolerance checks one property of a proposed point; a real grasp also needs obstacle avoidance, timing, force limits, and uncertainty handling.
Three ways to organize computation
| Architecture | What is shared | Main tradeoff |
|---|---|---|
| Unified model | Many capabilities use shared parameters or representations | Shared learning may transfer useful structure, but updates can interfere |
| Modular system | Independent specialists connect through explicit interfaces | Components can be updated separately, but coordination and compatibility need testing |
| Hybrid | Some representations or processing are shared, while other components specialize | Flexible boundaries add design choices and evaluation work |
None is automatically best. A single model may handle several tasks well. Separate vision, speech, planning, and control systems may need different data or computational operations. Compare complete systems under relevant constraints rather than counting their modules.
Choose what crosses the boundary
Text is flexible and readable. The sentence “the cup is on the right” communicates a broad location but loses precise coordinates. That is a limitation of this particular summary, not proof that language cannot express numbers: “x = 60 cm, y = 30 cm in the table frame” preserves much more. Inspect what the actual message retains.
Structured records make fields, units, and constraints explicit. The lab sends an object type, coordinate frame, unit, x, and y. The receiver rejects a missing unit instead of guessing. A structured record can still be incorrect; validation needs both schema checks and tests against the world.
Continuous vectors can represent rich learned information. Their meanings depend on the transformations that produce and consume them. Two independently trained models need not agree about coordinate meanings even if both use vectors of the same length. Our hand-defined example makes this visible: [y in cm, x in cm] cannot be passed straight to a consumer expecting [x in m, y in m].
An adapter transforms one representation into another. The lab’s adapter swaps and scales known coordinates. In more complex systems an adapter may be learned from paired examples; learning it and evaluating generalization require a separate experiment. A conversion cannot recover information the sender has already discarded without relying on additional assumptions or evidence.
Test meaning, not just shape
Scaling the lab’s vector without swapping it produces an in-bounds but wrong target at asymmetric positions. At x = y, the bug disappears. This illustrates why one easy successful example is weak evidence for compatibility. Test asymmetric coordinates, boundary cases, missing metadata, and changes in the upstream component.
For a chessboard, prose may describe a threat, a structured board can preserve every piece and whose turn it is, and a latent vector may help a learned evaluator. An exact move checker needs a board representation with the necessary rules and history; a vague summary alone cannot establish move legality. Choose the representation according to the downstream question.
Graphs preserve relations
The source’s video example combines visual event detection and speech transcription, potentially computed in parallel. An event graph can retain event nodes, timestamps, sources, and relations such as “before,” “after,” or “refers to.” Flattening everything into one sentence may hide which component observed what.
The lab’s two supplied events show a cup placement at 2 seconds and speech at 3 seconds. An audio clock offset changes the apparent order. Correcting known offsets aligns the timeline; it does not prove the speech is truthful or that one event caused another. Real event fusion also needs uncertainty, identity matching, and handling of missing or contradictory evidence.
Internal experts are a different boundary
An internal mixture-of-experts layer routes activations through selected expert blocks inside a network, often for individual tokens. A modular system selects independent full models or tools for subtasks. They both use specialization, but their interfaces, training, and decision granularity differ. A modular system can itself contain a language model with MoE layers. Review the distinction between total and active weights in compute budgets.
Design a cup-picking interface
For the source exercise, assign information to each responsibility: language can state “pick up the red cup”; a structured world state can store object identity, pose, frame, units, uncertainty, and obstacles; continuous control values can specify bounded joint targets or velocities at the required rate. Preserve timestamps across the handoffs. A controller should stop or seek better evidence when a necessary constraint is missing.
The goal is not to force every specialist into one format. It is to preserve the distinctions that the next computation needs and verify that the components interpret them compatibly.
A robot needs to pick up a cup. Which interface design best fits the different responsibilities?
Take this idea with you.
Specialists need interfaces that preserve relevant distinctions. Validate schema, units, frame, and meaning; test counterexamples that could reveal a broken handoff.
Explore related topics and the topic map
How this topic connects
Explore this topic on the interactive mapUse these connections to review a foundation or choose where to go next. You can open any topic without completing the others.
What it builds on
- Vectors and matrices
Treat a list of numbers as one representation and trace weighted sums. These operations connect the lesson’s inputs to its outputs.
- Embeddings
Compare meanings represented as numbers so you can reason about search results and the information a representation loses.
- Tools and evidence
Build assistants that inspect tool results and recover from failures instead of treating every returned value as trustworthy.
Compare prose, structured records, and vectors; diagnose lost information and mismatched coordinate meanings.
What it enables
- Learn a shared representation contract
Diagnose why two models fail to communicate even when each works on its own.
- Share the right information at the right time
Choose what collaborating components need to share so important information survives limited space and attention.
- Coordinate dependencies and reusable skills
Coordinate multi-step work without duplicate actions or decisions based on stale results.