portaljs-define-schema

1# PortalJS — Define Schema
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3## Overview
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5Define a dataset's metadata profile — the **authoring** skill for the metadata-profile
6contract (`lib/metadata`). Where `portaljs-add-dataset` registers *that* a dataset exists,
7this skill describes *what its data means*: infer a Frictionless **Table Schema** (fields,
8types, constraints) from sampled data, add the **Data Package** fields a catalog surfaces
9(title, licenses, sources, keywords), and write them onto the dataset's entry in
10`datasets.json`. The showcase at `/@<namespace>/<slug>` then renders a typed field table
11instead of a bare preview. The model is Frictionless-native; DCAT is a serialization layer
12built on top later, not authored here.
13 
14The skill runs on a profile ladder — reach for higher levels only when needed:
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16| Level | What it is | When |
17| --- | --- | --- |
18| L0 | Default `frictionless-tabular` profile; declare schema + metadata. | Default. Standard tabular CSV/TSV. |
19| L1 | L0 plus extra descriptive package fields. | Extra metadata, standard validation is fine. |
20| L2 | Fully custom profile (own schema template + `validate()`). | A dataset type needing custom validation rules. |
21| L3 | Multiple registered profiles, resolved per dataset. | A portal mixing dataset types. |
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23The skill is interactive and never dead-ends: if input is thin it interviews in short
24rounds, infers defaults from the data, echoes the schema for confirmation, and accepts
25"use defaults" to proceed with the inferred schema as-is.
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