kempersc 7f53ec6074 docs(person_pid): add PPID-GHCID alignment and PiCo comparison docs

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PiCo vs PPID: Comparative Analysis

Version: 0.1.0
Last Updated: 2025-01-09
Related: PPID-GHCID Alignment | PiCo Ontology Analysis

1. Executive Summary

This document compares the PiCo (Persons in Context) ontology developed by CBG|Centrum voor Familiegeschiedenis with our proposed PPID (Person Persistent Identifier) system. The analysis is based on deep research into PiCo's implementation in Open Archives (openarchieven.nl) and the WieWasWie platform.

1.1 Key Finding

PiCo and PPID serve complementary purposes:

System	Primary Purpose	Identifier Style	Scope
PiCo	Data model for person observations in genealogical sources	Opaque UUIDs	Genealogical records (civil registries, church books)
PPID	Persistent identifiers for heritage sector persons	Semantic geographic-temporal	Heritage custodian staff and historical figures

Recommendation: PPID should adopt PiCo's ontological distinctions (PersonObservation vs PersonReconstruction) while using its own semantic identifier format aligned with GHCID conventions.

2. PiCo Architecture (From Research)

2.1 Core Classes

From the PiCo specification at personsincontext.org/model:

┌─────────────────────────────────────────────────────────────────┐
│                         PiCo MODEL                               │
├─────────────────────────────────────────────────────────────────┤
│                                                                  │
│  ┌─────────────────────────────────────────────────────────┐    │
│  │                     Person                                │    │
│  │        (Container class - not used directly)             │    │
│  │                                                          │    │
│  │    ┌─────────────────┐    ┌─────────────────┐           │    │
│  │    │ PersonObservation│    │PersonReconstruction         │    │
│  │    │                 │    │                 │           │    │
│  │    │ - Data as found │    │ - Curated identity│          │    │
│  │    │   on Source     │    │ - Links multiple │          │    │
│  │    │ - hadPrimarySource   │   observations   │          │    │
│  │    │ - hasRole       │    │ - wasDerivedFrom │          │    │
│  │    │ - hasAge        │    │ - wasGeneratedBy │          │    │
│  │    │ - hasOccupation │    │ - wasRevisionOf  │          │    │
│  │    └─────────────────┘    └─────────────────┘           │    │
│  └─────────────────────────────────────────────────────────┘    │
│                                                                  │
│  ┌─────────────────────────────────────────────────────────┐    │
│  │                     Source                                │    │
│  │  (schema:ArchiveComponent)                               │    │
│  │  - name, dateCreated, holdingArchive, associatedMedia   │    │
│  └─────────────────────────────────────────────────────────┘    │
│                                                                  │
│  ┌─────────────────────────────────────────────────────────┐    │
│  │                   PersonName (PNV)                        │    │
│  │  - literalName, givenName, baseSurname, surnamePrefix   │    │
│  │  - patronym, initials                                    │    │
│  └─────────────────────────────────────────────────────────┘    │
│                                                                  │
└─────────────────────────────────────────────────────────────────┘

2.2 PiCo Identifier Structure in Open Archives

From the Open Archives API documentation:

URI Format: https://www.openarchieven.nl/{3-letter-archive-code}:{uuid}[/{token}]

Examples:
- https://www.openarchieven.nl/rat:48c2b836-385f-11e0-bcd1-8edf61960649
- https://www.openarchieven.nl/elo:f5169776-db74-70a3-51e3-20c15291429c

Components:
- rat = Regionaal Archief Tilburg (3-letter archive code)
- 48c2b836-385f-11e0-bcd1-8edf61960649 = UUID of the record
- /ttl:pico = Optional token for content negotiation (Turtle + PiCo profile)

2.3 PiCo PersonObservation Example (Actual Data)

From Open Archives API response:

@prefix oa: <https://www.openarchieven.nl/id/> .
@prefix pico: <https://personsincontext.org/model#> .
@prefix prov: <http://www.w3.org/ns/prov#> .
@prefix sdo: <https://schema.org/> .

oa:record_rat_48c2b836-385f-11e0-bcd1-8edf61960649_Person_22f30464-3867-11e0-bcd1-8edf61960649
    a pico:PersonObservation ;
    prov:hadPrimarySource oa:record_rat_48c2b836-385f-11e0-bcd1-8edf61960649 ;
    pico:hasRole "Moeder" ;
    sdo:children oa:record_rat_48c2b836-385f-11e0-bcd1-8edf61960649_Person_22f2ae9c-... ;
    sdo:spouse oa:record_rat_48c2b836-385f-11e0-bcd1-8edf61960649_Person_22f2da16-... ;
    sdo:gender sdo:Female ;
    sdo:name "Cornelia Verhulst" ;
    sdo:familyName "Verhulst" ;
    sdo:givenName "Cornelia" .

2.4 PiCo PersonReconstruction Example

From PiCo specification:

cbg:person_reconstruction_2
    a pico:PersonReconstruction ;
    sdo:name "Anna Maria Koppen" ;
    sdo:familyName "Koppen" ;
    sdo:givenName "Anna" ;
    sdo:gender sdo:Female ;
    sdo:birthPlace "Haarlem" ;
    sdo:birthDate "1860-03-31"^^xsd:date ;
    sdo:deathPlace "Detroit, VSA" ;
    sdo:deathDate "1926"^^xsd:gYear ;
    prov:wasDerivedFrom nha:huwelijksakte_1885_321_po_1, 
                        cbg:NL-HaCBG_1755_0341_142_po_1 ;
    prov:wasGeneratedBy cbg:reconstruction_activity_01 .

3. Detailed Comparison

3.1 Identifier Format

Aspect	PiCo (CBG/Open Archives)	PPID (Proposed)
Format	`{archive}:{uuid}`	`{TYPE}-{FC}-{FR}-{FP}-{LC}-{LR}-{LP}-{CR}-{FT}-{LT}`
Example	`rat:48c2b836-385f-11e0-bcd1-8edf61960649`	`PID-NL-NH-AMS-NL-NH-HAA-19-20-JAN-BERG`
Human Readable	No (opaque UUID)	Yes (semantic components)
Archive Prefix	Yes (3-letter code)	No (implicit via source)
Geographic	No	Yes (birth + death locations)
Temporal	No	Yes (century range)
Name	No	Yes (first + last token)

3.2 Conceptual Model

Concept	PiCo	PPID
Raw Observation	`PersonObservation`	Observation (separate system)
Curated Identity	`PersonReconstruction`	`PID` (promoted from `ID`)
Temporary State	Not explicit	`ID` class
Permanent State	All URIs persistent	`PID` class only
Provenance	PROV-O (wasGeneratedBy, wasDerivedFrom)	PROV-O + XPath claims
Name Vocabulary	PNV (Person Name Vocabulary)	Emic labels from sources

3.3 Persistence Philosophy

Aspect	PiCo	PPID
All identifiers persistent?	Yes	No - only PID class
Temporary identifiers?	No explicit concept	Yes - ID class
Promotion mechanism?	N/A	ID → PID when criteria met
Epistemic uncertainty?	Implicit (multiple observations)	Explicit (ID vs PID distinction)
Living persons?	Can have PersonReconstruction	Must remain ID until death

3.4 Geographic Handling

Aspect	PiCo	PPID
In identifier?	No	Yes
In properties?	Yes (birthPlace, deathPlace)	Also yes
Format	Free text or URI	ISO 3166-1/2 + GeoNames
Historical mapping?	Encouraged (link to thesaurus)	Required (historical → modern)
Example	`sdo:birthPlace "Haarlem"`	`...-NL-NH-HAA-...`

3.5 Temporal Handling

Aspect	PiCo	PPID
In identifier?	No	Yes (century range)
Date format	ISO 8601 (xsd:date)	Century numbers
BCE support	Via negative years	Via negative centuries (-5--4)
Precision	Day-level possible	Century-level only in ID
Example	`sdo:birthDate "1860-03-31"^^xsd:date`	`...-19-20-...`

4. Key Differences Explained

4.1 Why PiCo Uses Opaque UUIDs

PiCo's design goals (from GitHub README):

Successor to A2A: Designed to replace XML-based Archive-to-Archive standard
Genealogical focus: Primary use case is WieWasWie ancestor search
Linked Data: Interoperability via RDF, not human-readable identifiers
Archive-centric: Identifiers include archive code prefix

PiCo's UUID approach is appropriate for:

Massive genealogical databases (millions of records)
Automated conversion from A2A
Machine-to-machine data exchange

4.2 Why PPID Uses Semantic Identifiers

PPID's design goals:

GHCID alignment: Consistent identifier philosophy across GLAM project
Heritage sector focus: Staff of heritage institutions, historical figures
Human discovery: Identifiers aid browsing and deduplication
Epistemic honesty: Explicit distinction between ID (uncertain) and PID (verified)
Scholarly citation: Identifiers can be meaningfully cited in publications

PPID's semantic approach is appropriate for:

Smaller, curated datasets
Human curation workflows
Cross-system deduplication
Scholarly reference

4.3 The ID/PID Distinction (Unique to PPID)

PiCo assumes all identifiers are permanent once created. PPID introduces explicit epistemic states:

PiCo:
  PersonObservation (always permanent)
      ↓ prov:wasDerivedFrom
  PersonReconstruction (always permanent)

PPID:
  Observation (separate system, permanent)
      ↓
  ID (temporary, may change)
      ↓ promotion when criteria met
  PID (permanent, never changes)

Why this matters for heritage sector:

Living persons: Cannot have verified death observation → must remain ID
Incomplete records: May never have enough data for PID promotion
Ongoing research: Archives not yet explored → cannot claim PID status
Scholarly integrity: Prevents overclaiming certainty

5. Integration Recommendations

5.1 Adopt PiCo Ontological Distinctions

PPID should use PiCo's class hierarchy:

@prefix ppid: <https://ppid.org/> .
@prefix pico: <https://personsincontext.org/model#> .

# PPID extends PiCo
ppid:PersonID rdfs:subClassOf pico:PersonReconstruction .
ppid:PersonPID rdfs:subClassOf pico:PersonReconstruction .

# PPID observations link to source observations
ppid:hasSourceObservation rdfs:subPropertyOf prov:wasDerivedFrom ;
    rdfs:range pico:PersonObservation .

5.2 Maintain PPID Semantic Identifier Format

Do not adopt PiCo's opaque UUID format. Keep semantic GHCID-aligned format:

PID-NL-NH-AMS-NL-NH-HAA-19-20-JAN-BERG

Rationale: GHCID project-wide consistency, human discoverability, scholarly citation.

5.3 Use PNV for Name Properties

Adopt PiCo's use of Person Name Vocabulary for structured name data:

ppid:PRID-... pnv:hasName [
    a pnv:PersonName ;
    pnv:literalName "Jan van den Berg" ;
    pnv:givenName "Jan" ;
    pnv:surnamePrefix "van den" ;
    pnv:baseSurname "Berg"
] .

5.4 Use PROV-O for Provenance

Adopt PiCo's PROV-O patterns for reconstruction provenance:

ppid:PID-NL-NH-AMS-...
    prov:wasDerivedFrom <observation-1>, <observation-2> ;
    prov:wasGeneratedBy [
        a prov:Activity ;
        prov:startedAtTime "2025-01-09T00:00:00"^^xsd:dateTime ;
        prov:wasAssociatedWith ppid:curator-001
    ] .

5.5 Separate Observation Identifiers

As noted in the revised PPID design, observations use a different identifier system:

{REPOSITORY_GHCID}/{CREATOR_GHCID}/{RiC-O-PATH}

Example:
NL-NH-HAA-A-NHA/NL-NH-HAA-A-NHA/burgerlijke-stand/geboorten/1895/003/045

This is distinct from PiCo's {archive}:{uuid} but serves similar purposes.

6. Resolved Open Questions

Based on user clarifications:

6.1 BCE Date Handling

Resolution: Use negative century numbers.

Format: {first_century}-{last_century}

Examples:
- 5th century BCE to 4th century BCE: "-5--4"
- 1st century BCE to 1st century CE: "-1-1"
- 5th century BCE to 3rd century CE: "-5-3"

This aligns with ISO 8601 extended format which uses negative years for BCE dates.

6.2 Non-Latin Script Transliteration

Resolution: Apply same transliteration rules as GHCID (documented in AGENTS.md).

Script	Standard
Cyrillic	ISO 9:1995
Chinese	Hanyu Pinyin (ISO 7098)
Japanese	Modified Hepburn
Korean	Revised Romanization
Arabic	ISO 233-2/3
Hebrew	ISO 259-3
Greek	ISO 843

6.3 Disputed Locations

Resolution: Not a PPID concern - handled by ISO standardization.

When historical locations are disputed:

Use the ISO-standardized modern location
Document the dispute in observation metadata
Do not encode uncertainty in the identifier itself

6.4 Living Persons

Resolution: Living persons are always ID class and can only be promoted to PID after death.

def can_promote_to_pid(person_id: str, observations: list) -> bool:
    """
    Check if ID can be promoted to PID.
    
    Living persons can NEVER be promoted.
    """
    # Check for death observation
    death_obs = [o for o in observations if o.is_death_record or o.is_post_death]
    
    if not death_obs:
        # No death observation = person may be alive = cannot be PID
        return False
    
    # Continue with other promotion criteria...
    return check_other_criteria(observations)

Rationale:

PID requires verified last observation (death)
Living persons have incomplete lifecycle
Future observations may change identity assessment
Privacy considerations for living individuals

7. Implementation Alignment

7.1 Class Mapping

PiCo Class	PPID Equivalent	Notes
`pico:Person`	(Container)	Not used directly
`pico:PersonObservation`	Observation (separate system)	Different identifier format
`pico:PersonReconstruction`	`ppid:PersonID` or `ppid:PersonPID`	Split by epistemic certainty
`pico:Source`	`schema:ArchiveComponent`	Same as PiCo
`pnv:PersonName`	`pnv:PersonName`	Adopt PNV

7.2 Property Mapping

PiCo Property	PPID Usage	Notes
`prov:hadPrimarySource`	Same	For observations
`prov:wasDerivedFrom`	Same	PRID from POIDs
`prov:wasGeneratedBy`	Same	Activity provenance
`prov:wasRevisionOf`	Same	Version history
`sdo:birthDate`	Same	In properties
`sdo:birthPlace`	Same + in identifier	Dual representation
`sdo:deathDate`	Same	In properties
`sdo:deathPlace`	Same + in identifier	Dual representation
`pico:hasRole`	Same	For observations
`pico:hasAge`	Same	When birthDate unknown

7.3 Namespace Declarations

@prefix ppid: <https://ppid.org/> .
@prefix pico: <https://personsincontext.org/model#> .
@prefix pnv: <https://w3id.org/pnv#> .
@prefix prov: <http://www.w3.org/ns/prov#> .
@prefix sdo: <https://schema.org/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

8. Conclusion

8.1 What PPID Adopts from PiCo

PersonObservation/PersonReconstruction distinction - Core ontological pattern
PROV-O provenance model - wasDerivedFrom, wasGeneratedBy, wasRevisionOf
Person Name Vocabulary (PNV) - Structured name representation
Schema.org properties - birthDate, deathDate, birthPlace, deathPlace, etc.
Source linking - hadPrimarySource, holdingArchive

8.2 What PPID Does Differently

Semantic identifier format - Geographic-temporal-emic instead of opaque UUID
ID/PID epistemic distinction - Explicit uncertainty modeling
Living person handling - Must remain ID until death
GHCID alignment - Consistent with heritage custodian identifier philosophy
Century range encoding - Temporal disambiguation in identifier
Emic label tokens - Name components in identifier for discoverability

8.3 Interoperability Path

PPID can be fully interoperable with PiCo systems via:

OWL mappings: ppid:PersonPID rdfs:subClassOf pico:PersonReconstruction
SPARQL federation: Query across PPID and PiCo endpoints
Bidirectional links: owl:sameAs between PPID and PiCo identifiers
Profile negotiation: Serve data in PiCo format via content negotiation

9. References

PiCo Resources

PiCo Specification: https://personsincontext.org/model
PiCo GitHub: https://github.com/CBG-Centrum-voor-familiegeschiedenis/PiCo
Open Archives API: https://www.openarchieven.nl/api/docs/uri.php
CBG: https://cbg.nl/

Standards

Person Name Vocabulary (PNV): https://w3id.org/pnv
PROV-O: https://www.w3.org/TR/prov-o/
Schema.org: https://schema.org/

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