# Motivating Examples: Describing persons

## Introduction

People are temporal entities, which makes it problematic to describe them [atemporally using RDF](https://www.w3.org/TR/rdf11-concepts/#change-over-time).

Many vocabularies have a simple design, defining direct properties and relationships (`name`, `height`, `knows`, `interest`, `worksFor`, etc.). If any of those are not permanent facts, such properties are in some ways too simple. One example of a vocabulary designed to handle this variance is PROV. It does so by [defining qualified versions](https://www.w3.org/TR/2013/REC-prov-o-20130430/#description-qualified-terms) of its simple, atemporal properties.

With RDF-star (by describing occurrences of triples), this design pattern is no longer strictly necessary. Even when properties appear to be too simple for certain, detailed use cases, it is possible to ascribe qualifed information on the relationship, without defining event-based classes and qualified relationships to relate them.

:::info
NOTE: If event-based things are foreseen early on in the design of a vocabulary, it is often a better practice to design for those directly, and avoid this problem altogether. In a way, annotating relationships is not much more than "marginalia", and as such might not readily appear as a natural part of a domain model.
:::

There are also occasional needs to describe statements in general in more detail. You may want to further comment on it, qualify it if it is still not granular enough, and/or ascribe sources of certain facts. Historically, either RDF reification or structured literals (with `rdf:value` for the actual value) have been used for this.

Here too RDF-star (by describing occurrences of triples) can support these needs without remodelling the simpler data.

Finally, there are needs for describing claims that are not necessarily believed in (asserted in the graph), such as suggested or disputed facts about persons.

## Examples

Preamble:

PREFIX sdo: <https://schema.org/>

### Married Twice

(An "on-and-off" relationship.)

<elizabethtaylor> a sdo:Person ;
    sdo:spouse <richardburton> {| :startDate "1964" ; :endDate "1974" |} ;
    sdo:spouse <richardburton> {| :startDate "1975" ; :endDate "1976" |} .

### Commenting on Facts

<elizabethtaylor> a sdo:Person ;
    sdo:birthDate "[phone]T00:00:00Z"^^xsd:dateTime {|
        sdo:comment "Too precise, use less granular date datatype."@en |} ;
    sdo:birthPlace <Hampstead> {|
        sdo:comment "Specifically Hampstead Garden Suburb"@en |} .

### Suggesting Facts

<< <elizabethtaylor> sdo:sameAs wd:Q34851 >>
    sdo:comment "These are the same person."@en .
    
<< <elizabethtaylor> sdo:spouse <richardburton> >>
    sdo:comment "This is no longer true."@en .
    
<< <elizabethtaylor> sdo:knows <richardburton> >>
    sdo:comment "They do know each other."@en .