Model specification

Field types and constraints

Every field declares a type:

• string: text.
• email: text matching ^[^\s@]+@[^\s@]+\.[^\s@]+$; mailbox existence is not checked.
• integer: a finite number without a fractional part.
• number: a finite number.
• boolean: true or false.
• latitude: a finite number in decimal degrees, from -90 to 90 inclusive.
• longitude: a finite number in decimal degrees, from -180 to 180 inclusive.
• date: a valid date string in YYYY-MM-DD format.
• datetime: a valid UTC datetime string in YYYY-MM-DDTHH:MM:SSZ format.

Coordinate types already include their geographic bounds. Missing values are governed by requiredness.

Optional constraints are:

• mandatory: requires a filled value; omitted means false.
• required_field: requires a value when the named field on the same sheet is filled.
• enum: a nonempty list of distinct, non-null values matching the type, bounds and pattern.
• minimum, maximum: inclusive numeric bounds; integer bounds must be whole numbers.
• maximum_field: the value must not exceed the named numeric field on the same sheet; compare only valid, present values.
• pattern: a PCRE regular expression for string, email, date or datetime fields.
• sequence: consecutive integer numbering in worksheet order, grouped by same-sheet fields. Declare sequence: {start: 1, group_by: [trip_id, catch_id]} on an integer or string table field.
• unique: requires distinct values within a repeated table field.
• reference: a catalogue, table and named lookup.

Enums are constraints, not a separate type. Quote numeric-looking string codes: enum: ["01", "02"].

For conditional fields, required_field: length makes the unit required when length is filled, including zero.

In tables, this applies within the same row. A field cannot depend on itself; mutual dependencies are allowed.

The condition still permits a unit when length is empty.

Reference bindings default to error severity. Use severity: warning for a warning.

Declare tables under freely named catalogues:

references:
  people: [contacts]

Bind the field to a table and lookup:

contact_email: {location: C4, type: email, reference: {catalogue: people, table: contacts, lookup: email, severity: warning}}

Catalogue names have no built-in meaning. Matching settings and reference data belong outside the model.

See ?form_fields for the effective field properties returned by accessors.

Workbook layouts

sheets is an ordered mapping of worksheet names. Every declared sheet is required; names are unique ignoring case.

Each sheet has a layout, an optional primary_key, and fields, keyed by local field name.

• kind: cells: requires column_count. Each field needs a unique uppercase A1 location, such as E3.
• kind: table: requires start_row. Field order defines columns; omit field location and layout column_count.

Table column counts are derived from the fields. An explicit column_count must match that count.

Rows before start_row are preamble.

An optional row_count declares the exact physical row count. Fixed locations must fit declared dimensions.

Coordinates are one-based. An empty sheet can declare fields: {}; an empty table derives a column count of zero.

Primary keys

A table can declare one field or an ordered combination of fields as its primary key:

primary_key: [station, observation_id]

Every component must be filled; the combination identifies one row within that sheet of a submitted form.

Individual components may repeat in a composite key. Field-level unique still means individual uniqueness.

Use local field names. Keys must be nonempty, contain no repeated fields, and reference declared table fields.

Omit primary_key when no key is defined. Fixed-cell sheets cannot declare a primary key.

form_sheets() and form_definition() retain the declaration without changing field constraints.

This package checks key definitions. Checking submitted key values belongs to the validation package.

Optional composite keys and row completeness

Table sheets can declare these independent constraints:

unique_key: [station, category]
at_least_one: {fields: [category, count], severity: warning}

unique_key checks uniqueness only when every component is supplied and correctly typed. It does not make its fields mandatory. Every occurrence of a duplicate complete key is reported as an error. A sheet may declare both a primary key and a unique key; they are checked independently. Parent relationships continue to reference a parent’s primary key.

at_least_one requires a supplied value in at least one selected field on each populated row. A row is populated when any declared field has a supplied value after preparation. Entirely empty rows are skipped. Zero and false count as supplied values. Both constraints use the validation engine’s configured missing-value policy.

Both field lists must be nonempty, contain no duplicates, and name declared fields in the same table. at_least_one accepts error, warning, or info; omitted severity defaults to error.

YAML conventions

Use one UTF-8 document. Tags, anchors, aliases, merges, directives and document markers are unsupported.

Mapping keys must be unique strings. Unknown properties are errors.

Quote versions and codes, especially leading-zero codes such as "01".

Use true and false for booleans. Quote text codes such as "yes", "no", "on" and "off".

Empty YAML values, null and ~ mean null; "" means an empty string. Omit unused optional properties.

Identifiers start with an ASCII letter, followed by letters, digits, dots, underscores or hyphens.

Full field IDs combine the sheet and field names: <sheet>.<field>.

Write field properties in this order: mandatory when true, location for cells, type, required_field, then constraints.

schema_version: "1.0.0" selects the package contract. form.version independently identifies your model version.

Change form.version when the model meaning changes. New schema properties require a supported contract version.

Definition checks

Load a file with read_form_model() to check its structure and consistency.

Use check_form_model() on a definition list to get diagnostics with source, property path and message.

Consistency checks run only after structure passes. Submitted-data validation belongs to form.validation.