1.1.3.9. Summary

This page summarises the WHG v4 data model on one page, and says where each part is described in full. The model is PLATO, the Place Attestation Ontology, at PLATO 0.7.1 (doi:10.5281/zenodo.23060220; all versions: doi:10.5281/zenodo.21688313); the terms below are PLATO’s unless they are marked as WHG’s own practice.

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1.1.3.9.1. The idea in one paragraph

What is known about a place is not a record with one value per field but a set of attestations: claims, each made by a particular source, with its own dates and certainty, and recorded by a particular contributor. Sources that disagree sit side by side; nothing is overwritten, and every claim can be traced to its evidence. See the Introduction.

1.1.3.9.2. Key entities

Entity	In brief	Read more
SpatialEntity	A stable identity on which attestations converge. It carries a display label and finding aids (ccodes, entityIdentifier), and nothing else of its own. PLATO has no Place class: what kind of thing an entity is, is attested.	Overview
Attestation	A bundle of claims about exactly one SpatialEntity (attests_about), with its sources, certainty, contributor and dates.	Attestations and Relations
Name, Geometry, Timespan, Type, PropertyValue	The facets an attestation bundles (attests_name, attests_geometry, attests_timespan, attests_type, attests_property). Each is a node of its own and may be qualified on its own.	Overview
Authority	What attestations rest on: a Source, Dataset, Period, RelationType or CertaintyLevel. A Citation is one attestation’s use of one source, with a locator.	Overview
IdentityRelation	A claim that two SpatialEntities are the same (exactMatch), nearly so (closeMatch), related, or of unspecified kind.	Identity below
Candidate	A match suggested by software, awaiting review. Not a claim.	Candidates, clusters and loci
Gazetteer, GazetteerGroup	The workspace that holds contributed data, and a group of such workspaces.	Gazetteers, collections, groups and periods below
Contributor	The person, team or process that makes attestations. WHG requires an ORCID for new contributions; earlier data keeps its existing attribution.	Overview

The entity–relationship diagram shows how they link.

1.1.3.9.3. Attestation

An attestation says: according to this source, this SpatialEntity had this name (or location, date range, type, relation or other attribute) during this time, with this degree of certainty. Besides what it bundles, it carries what is true of the claim as a whole:

• its sources (sources), or citations with a locator (citations);

• certainty, as a number (certainty) or a word (certaintyLevel), with a certaintyNote;

• whether the source denies what is bundled (negated), and how firmly it asserts it (sourceStance);

• whether software computed it rather than a source giving it (computed);

• who made it and when (contributor, created, modified), and, for a member of a route, itinerary or network, its position (sequence).

Certainty is not fuzziness. Certainty is how sure we are of a claim, which better evidence can change; fuzziness is vagueness in the thing itself, such as a frontier zone. PLATO records them separately, in a facet’s qualification. Precision uses the schema’s own values: startPrecision and endPrecision (day, month, year, decade, century, era, geological_period) on a Timespan, and spatialPrecision (exact, approximate, uncertain, historical_approximate) on a Geometry. See Qualifications and Denial and the source’s stance.

Geometries from different sources, or for different dates, are separate geometry attestations; several geometries that one source gives together may share an attestation, each with a role. PLATO does not accept a GeoJSON GeometryCollection.

1.1.3.9.4. Relations

An attestation may relate its SpatialEntity to one other entity: relates_to gives the target and has_relation_type the kind, a RelationType. The relation therefore has a source, dates and a certainty like any other claim. PLATO’s relation types are:

Purpose	Relation types
Containment	ContainedIn (contained_in / contains)
Routes, itineraries and networks	MemberOf (with sequence), ConnectedTo, LeadsTo; for segments BeginsAt, EndsAt, HasEnd
Places in the histories of people, objects and events	BirthplaceOf, DeathplaceOf, ResidenceOf, WorkplaceOf, FindspotOf, SettingOf
Images and records about a place	DepictedIn, SubjectOf

Containment is not membership. A parish in a hundred is ContainedIn it, for the attested timespan and according to the attested source, and a place may be attested in different containers at different times. MemberOf is membership of a route, itinerary or network: a town on a road is not within the road. Direction is carried by the relation type alone (LeadsTo is directed, ConnectedTo is not). For people, objects, events, images and records, the target is that thing’s own IRI, named with a relatedLabel. A project may declare its own relation types in a PLATO JSON document’s relationTypes, each narrowing one of PLATO’s with broaderRelation; PLATO’s spreadsheet tables take only PLATO’s own. See Relation types and Routes, Itineraries, Networks, Groups and Periods.

1.1.3.9.5. Identity

That two SpatialEntities are the same place is also a claim. An IdentityRelation is bundled in an attestation (attests_identity, JSON identities), so it has a source, a contributor and a date.

• It is one attributed claim among many, never a canonical fact. WHG does not merge records or mint new identifiers because of it.

• exactMatch may be chained only within one attestation, and the other identity types are never chained. That A is B (said by one person) and B is C (said by another) does not mean anyone said A is C.

• “These are not the same” is an attestation with negated: true around one exactMatch.

• A Candidate (plato:Candidate) is a suggestion made by software, such as the matches Map your Data offers for review. It is not a claim until a person confirms it.

• A cluster is not in PLATO: in WHG it is the result of a query in the Atlas, and a locus is its citable form (WHG place#172). Accepting a cluster of n records is one attestation bundling the n−1 exactMatch relations actually made.

See Identity.

1.1.3.9.6. Meta-attestations

Because an attestation has an identity of its own, another attestation can comment on it (meta_attestation_about, with its kind given by has_meta_type; JSON meta). PLATO’s meta types are Contradicts, Supports, Supersedes, Refines, Challenges, Bundles, DerivedFrom, Annotates, AlternativeTo and Retracts.

Once a Gazetteer is published its attestations are append-only: a correction is a new attestation that supersedes the old, and a withdrawal is a Retracts meta-attestation. The state at any date is the attestations created by then, less those superseded or retracted by then, so any earlier state can be reproduced and cited. See Meta-attestations.

1.1.3.9.7. Gazetteers, collections, groups and periods

• A Gazetteer (plato:Gazetteer, a dcat:Dataset) is a versioned workspace, owned by a contributor or team, with a title, creators, a licence, a version and a status (draft or published). It defines its own SpatialEntities, and may also hold attestations about other Gazetteers’ entities without redefining them. Every contribution becomes a Gazetteer. See Contributions and Attestations about other Gazetteers’ places.

• A WHG place collection is a curatorial act, and so a Gazetteer, not a SpatialEntity. Its annotations are attestations by its curator about other Gazetteers’ places, shown on those places’ pages only if the collection declares them public. Teaching and class groups are features of the WHG application, not of PLATO. See Place collections.

• A gazetteer group (plato:GazetteerGroup) groups Gazetteers, not places; a Gazetteer joins one with plato:member_of_group. See Gazetteer groups.

• A period is an Authority (plato:Period), optionally aligned with PeriodO, not a SpatialEntity. Places are dated by Timespans, which may refer to a period. See Periods.

• A route, itinerary, network or segment is a SpatialEntity with a Type attestation naming one of PLATO’s kinds, concepts in plato:EntityKindScheme: plato:TypeRoute, plato:TypeItinerary, plato:TypeNetwork and plato:TypeSegment. See Routes, Itineraries, Networks, Groups and Periods.

1.1.3.9.8. Computed values

A value that software works out from other statements in the same data, and that any consumer holding them could work out again (an itinerary’s span from its stops’ dates, a route’s line from its stations), is marked computed: true. It is not evidence: WHG marks it as computed when it shows or exports it, and never takes in anything marked computed as an attestation. A figure that a project works out from its own source material and publishes as a finding is attested, not computed. See Computed values and Computed extents.

1.1.3.9.9. Vocabularies

Controlled values come in three kinds: schema enumerations, written as plain strings and closed (temporal and spatial precision, identity type, citation function, authority type, gazetteer status); concept schemes, written as full IRIs and open to a project’s own concepts (meta types, source stance, geometry role, form status, kinds of spatial entity); and open string lists (name types, with the starter values toponym, chrononym, ethnonym, demonym, odonym and hydronym). A Type names its concept by full IRI in identifier. A Type node stands for one dataset’s use of a concept, so its own @id, if it has one, is never the concept’s IRI; it may also give the vocabulary (scheme) and its version (schemeVersion). See Vocabularies.

1.1.3.9.10. Formats and RDF

• Contributions: Map your Data, Linked Places Format (PLATO’s single-object profile, so LPF data is valid PLATO), PLATO JSON (place-centric or attestation-centric) and PLATO spreadsheet tables. RDF is not accepted for upload directly at v4.0: convert it to PLATO JSON first. See Contributions and Data formats in and out.

• RDF: PLATO is defined in RDF, and PLATO JSON becomes RDF through PLATO’s JSON-LD context. Each WHG place record has a persistent identifier that resolves through w3id.org, and that identifier is the place’s IRI. Today it answers software with JSON-LD in Linked Places Format, and Turtle is not served; at the v4 launch it will answer with PLATO JSON-LD or Turtle, with LPF still offered for existing clients. See RDF Representation and Identifiers and citation.

1.1.3.9.11. Storage

WHG holds the model in PostgreSQL/PostGIS, with Elasticsearch for search. These pages describe the model, not a storage layout.

1.1.3.9.12. What it is for

Finding a place as it was named at the time, dating by period, weighing sources that disagree, tracing what lay within what, reconciling a list of names, seeing one place across many gazetteers, modelling routes, journeys and networks, and citing a place in a gazetteer that changes: each is set out, with the part of the model it uses, in Use Cases.