Entity Linking and Knowledge Graph Construction › Provenance and Temporal Scope

A consumer may need to ask: where did this assertion come from, and when does it apply? Source provenance and temporal scope support different answers. Their required detail depends on the application; not every assertion needs a finite validity interval.

An old but accurately extracted source can describe a relation that no longer holds. Conversely, a current assertion can have weak source support. One timestamp cannot in general represent both when the relation applied and when the system recorded it. Keep those roles explicit when the query requirements distinguish them.

PROV-O provides classes and properties for representing entities, activities, agents, and their provenance relationships (W3C, 2013). For the extraction workflow here, useful record fields include:

• The source document identifier and, ideally, a content hash.
• The character span in the source that supports the assertion.
• The extractor name and version.
• The timestamp of extraction.
• A confidence score.

Retain the source version together with the span. Offsets into a mutable page can point to different text after an edit. A content hash identifies a version but does not recover its bytes, so keep a snapshot or another reliable retrieval route when reproduction matters. Record the offset convention, such as half-open Unicode character positions. The source text and locator let a reviewer inspect the asserted evidence; they do not prove that the assertion follows from it.

Some relations change over time, including employment and office holding. Wikidata statements can use qualifiers such as start and end time to record context. Its preferred, normal, and deprecated ranks are a separate mechanism. A normal rank is neutral about accuracy and currency, and several statements can have preferred rank. Rank alone does not determine whether a statement is valid on a requested date.

Wikidata's model is a good template even if you do not use RDF:

• Main claim: the item, property, and value; the statement record can also carry qualifiers, references, and rank.
• Qualifiers: additional context, such as time bounds, scope, or role.
• References point to sources that support a statement or document where its value came from.
• Rank: a preference or deprecation annotation, which can apply to several values.

Separating values, qualifiers, references, and ranks permits different assertions to be represented without collapsing their contexts. A consumer must still define how to handle disagreement, missing references, and temporal qualifiers. Neither references nor ranks are calibrated confidence probabilities.

Bitemporal modeling separates valid time, when an assertion applies in the modeled world, from transaction time, when it is recorded in the database (Jensen and Snodgrass, 2018). Suppose a fictional contract takes effect in 2020 but the database first records it in 2023. Its valid-time start is 2020 and its transaction-time start is 2023. The effective date must come from the evidence; an announcement date is not automatically an effective date. With the relevant retained history, the two axes distinguish a query about 2021 from a query about what was recorded as of 2022.

Before composing assertions, check that the relation-composition rule is sound for their meanings and that their temporal and other scopes align. Calibrated marginal probabilities alone do not determine a conjunction probability. Independence is sufficient for multiplying the marginals under the relevant probability model. With premise probabilities 0.9 and 0.8 but no dependence information, their conjunction can range from 0.7 to 0.8. A product score of 0.72 or a minimum score of 0.8 may instead be chosen as a heuristic, but must be labeled as such. A valid conjunction also does not establish an unsupported inference rule.