Preview & Hints

Preview is the feedback loop that keeps your model honest. It should be part of every modelling iteration, not reserved as a final validation step. The runtime preview runs your model against the mock runtime — the same runtime that answers your mock API — and shows the data next to hints that explain what is missing.

This page covers how previewing works, the hints the preview shows, and the iteration workflow that connects model changes to feedback.

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Preview panel showing data results and readiness hints side by side.

How Preview Works

1. The current model — the preview uses the current state of your tables, attributes, relations, mappings and operations.
2. The table's list operation — the preview runs the list operation the table's view is bound to, with its default page size and sort order.
3. Imported data — attributes bound to data columns return the values of the imported rows; relations are resolved one level deep.
4. Hints — if something prevents data from showing, the preview says what and links to the place to fix it.

Requests from the preview count toward your plan's request quota, like requests from your own code.

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Preview flow: model, list operation, imported data, hints.

Opening the Preview

Every table card on the Modelling Board has a play button in its header. Clicking it opens the Modelling Runtime Preview for that table, which combines view settings, live data and relation detail in one place.

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Play button on the modelling board table card.

Hints

Hint	Meaning	Action
Not mapped to imported data	The table is not bound to imported data, so the API returns no rows for it.	Bind the table and its attributes in the Mappings pane. See Data Sources.
No API binding	The view is not bound to a list operation, so no data can load.	Bind a list operation in the view settings. See API Design.
No identifier field	The view has no identifier field, so clicking a row opens no detail view.	Set the identifier field in the view settings.
No tables defined	The project has no tables yet.	Create tables on the modelling board.
Failed to load data	The request failed.	Retry; if it keeps failing, check the operation in API Design.

When a table is bound, the preview also tells you where its rows come from: imported data the table is mapped to, or values composed from imported value pools. In both cases nothing is invented.

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Runtime preview with a hint for a table that is not mapped yet.

The Iteration Workflow

The most productive modelling workflow is a tight loop between model changes and preview feedback — seconds, not minutes.

Recommended Sequence

1. Make a model change — add a table, modify an attribute, create a relation, or bind a mapping.
2. Open preview — run the table's list operation and inspect the results.
3. Resolve hints — follow the hint to the place that needs a change.
4. Update API design — adjust operation names, parameters or page sizes if needed. See API Design.
5. Repeat — until the preview shows the data you expect without hints.

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Diagram of the iteration workflow: model change, preview, hints, API update, repeat.

Why Short Cycles Matter

Delayed validation is the primary source of modelling rework. When you build ten tables before previewing, an issue in the first table may already have spread through relations. Previewing after each meaningful change keeps the corrective effort small.

What to Validate in Preview

Validation Area	What to Check	Related Page
Field readability	Are field names consistent? Use camelCase, avoid abbreviations.	Tables & Attributes
Data shape consistency	Do fields return the expected types?	Tables & Attributes
Relation behaviour	Does a 1:n relation return an array? Does a 1:1 relation return an object?	Relations
Mapping completeness	Is the table bound to imported data? Are the attributes your consumers need bound to columns?	Data Sources
Parameters and sorting	Do operation parameters narrow the result? Does sortField order it?	API Design

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Preview result inspection showing field types and relation nesting.

Common Preview Issues

Issue	Likely Cause	Fix
No rows at all	The table is not bound to imported data	Bind the table in the Mappings pane
Field returns null unexpectedly	The attribute is not bound to a data column	Bind the attribute to a column (Data Source mapping)
Relation returns an empty array	Wrong direction, wrong linking columns, or the target table is not bound	Review the relation definition. See Relations
Sort has no effect	sortField is not the name of an attribute bound to a data column	Use the name of a mapped attribute
Filter returns all records	The operation defines no parameter for that argument	Add the parameter in API Design

Preview on every plan

Free User

The runtime preview works the same on every plan, guest sessions included. Its requests count toward the request quota of your plan.

Iteration discipline

Registered User

Preview after every structural change. It catches type mismatches and relation direction errors that are easy to overlook during rapid modelling.

Team modelling workflows

Paid User

When several team members work on the same project, agree that every model change is previewed before moving on, so one person's incomplete work does not surprise the next.

Governance and readiness gates

Enterprise User

Use the preview as a readiness gate: a table is ready when the preview shows the expected data without hints. Include this check in your review workflow.

Related Pages

• Modelling Runtime Preview — the combined preview panel with view configuration, live data, and relation detail
• Tables & Attributes — attribute configuration and data mappings
• Relations — relation types, linking columns, and cardinality
• Data Sources — binding tables and attributes to the data pool
• API Design — operations, parameters and page sizes
• Modelling Board — the visual canvas where domain entities are created and arranged