Projections or derived datasets chapter

[pietercolpaert]

Introduce term

[pietercolpaert]

Projections and derived datasets

A projection is the result of a projection process on top of one or multiple LDES.
It is a derived stream that can be probabilistic or deterministic, and that can result in 1 ldes:EventStream or a tree:Collection when the objects would lose their immutability.
Projections MUST indicate what their source LDES is.

Views on top of the same collection

The source LDES is indicated as this server makes a different view on top of it:

<source-event-stream> a ldes:EventStream ;
    tree:view <myview>.
<myview> rdfs:comment "Geospatial repartitioning of the source’s members" .

Derived Event Streams

You MUST create a new URI for an LDES when there’s for instance a shape change or a resampling.

Using the predicate http://purl.org/pav/derivedFrom, the original LDESs are linked.

Derived Collections

You MUST create a new URI for a tree:Collection when there’s for instance a version materialization.

Using the predicate http://purl.org/pav/derivedFrom, the original LDESs are linked.

[pietercolpaert]

Snapshots/Version materializations

Also version materializations need to be described. This could look something like this:

<target> ldes:materialization [ 
	dcterms:temporal [ schema:startDate "2020-02-02" ; schema:endDate "..." ;
	dcat:accessUrl ?subject ;
	ldes:versionKey () 
] .

[pietercolpaert]

Some of these ideas have now been adopted in SDS: https://w3id.org/sds/specification