DRB Temporal Add-on

The DRB temporal add-on attaches temporal information to the product types that support it: applied to a DRB node, it returns the set of temporal properties declared for the node's topic — acquisition (sensing) period, processing date, modification date, validity period, and any other declared role. Declarations are tprl: RDF blocks attached to topic class URIs, loaded from installed TTL packages and Fuseki (the same double source as the core topic DAO).

Timezone policy

1. Every datetime returned by this add-on is timezone-aware and normalized to UTC. No naive datetime and no non-UTC zone can leave the add-on; cross-product comparison and sorting are safe by construction.
2. A parsed value carrying an offset (Z, +02:00, %z in a pattern) is converted to UTC; the original offset is not preserved.
3. A parsed naive value (no zone indication) is assumed UTC — the EO product convention. This is the only assumption in the system.

Usage

from drb.topics.resolver import create
from drb.addons.temporal import TemporalAddon, ACQUISITION, PROCESSING

node = create('S1A_IW_GRDH_...SAFE')
temporal = TemporalAddon().apply(node)
temporal.roles()                  # {ACQUISITION, PROCESSING, ...} — free
temporal[ACQUISITION].begin       # aware UTC datetime (lazy, memoized)
temporal[PROCESSING].at           # aware UTC datetime

Model overview

The tprl: descriptor vocabulary

Declarations live under the namespace http://knowledge-base.gael.fr/drb/addons/temporal/, prefix tprl:. Like the geoloc: vocabulary of the DRB geolocation add-on, this vocabulary carries extraction rules (how to obtain a value from a node), not data literals — block predicates live in the add-on namespace while role terms and the default format term reuse standard URIs.

The building block is a tprl:time blank node attached to a topic class URI. One block declares one role.

Roles are URIs. Where an established vocabulary types the notion exactly, its URI is reused; the add-on defines nothing redundant. The Dublin Core well-known set covers the common cases:

The vocabulary is controlled but extensible: any other URI is accepted as a role; the constants only make the common roles queryable without guessing strings.

Block rules

• tprl:role is mandatory and is a URI. A role declared more than once on the same topic is a conflict: every block carrying the duplicated role is skipped with a warning (RDF gives no order, so "first wins" would be non-deterministic).
• Shape: exactly one of
  • tprl:instant <source> — the role is an Instant;
  • tprl:begin <source> and/or tprl:end <source> — the role is an Interval; a single declared bound yields an open interval. Declaring both tprl:instant and a bound, or none of the three, skips the block with a warning.
• Source block: exactly one of tprl:xquery (XQuery program run against the node) or tprl:value (constant literal). Wrap the tprl:xquery expression in data(...) so extraction yields a plain string value rather than a node serialization or an empty sequence.
• Format: per source block, at most one of
  • tprl:format <uri> — a registered format term (default: xsd:dateTime);
  • tprl:pattern "<strptime>" — inline datetime.strptime pattern. Declaring both skips the block with a warning; an unknown tprl:format URI does too.
• A malformed block is skipped with a warning at load time — it never aborts loading globally.

Example

@prefix dct:  <http://purl.org/dc/terms/> .
@prefix tprl: <http://knowledge-base.gael.fr/drb/addons/temporal/> .
@prefix xsd:  <http://www.w3.org/2001/XMLSchema#> .

<https://knowledge-base.gael.fr/topics/sentinel-1#level-1-product> tprl:time [
    tprl:role dct:temporal ;                  # acquisition period
    tprl:begin [ tprl:xquery "data(//metadataSection//startTime)" ] ;
    tprl:end   [ tprl:xquery "data(//metadataSection//stopTime)" ] ;
] , [
    tprl:role dct:created ;                   # processing date
    tprl:instant [
        tprl:xquery "data(//processing/@stop)" ;
        tprl:pattern "%Y%m%dT%H%M%S" ;
    ] ;
] .

Topic-chain inheritance

Declarations are collected by walking the node's topic parent chain: a child topic overrides its parents on a per-role basis, so a subtype only needs to declare the roles it changes.

Formats

The format registry maps format term URIs to parser callables. The standard contract formats — the vocabulary's default, parsable with nothing else installed — are shipped in core:

Everything else is a satellite package. Mission-specific epochs (GPS time, seconds-since-epoch, Julian days, exotic calendars) register through the drb.addon.temporal.format entry point group; with tprl:pattern available inline, most knowledge bases need no satellite package at all.

Validation

temporal-validator file.ttl... performs static checks on tprl: descriptors: role present and unique per topic, shape exclusivity, source exclusivity, format term known or pattern present (not both).

Known limitation: the validator does not parse XQuery programs nor validate strptime patterns against sample values.