SECAI Core · phase 3 of 15 · noun

Semi-structured data

Data that is a mix of both structured and non-structured data.

The Explain card

Plain English: Semi-structured data mixes both worlds: it has some organising tags or keys, but not a rigid table layout. JSON, XML and log files are typical examples.
Example: A SIEM ingests JSON events from cloud services. Each record has fields, but different services include different fields, so the model must handle missing and extra keys.
Why it matters: Flexible formats let attackers smuggle unexpected fields, oversized values or injected text that parsers and models were not tested against. Schema validation matters even when the schema is loose.
Hook: Labelled boxes, but not all boxes hold the same things.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

The SIEM ingest job treats JSON cloud audit events as semi-structured data, then the feature encoder reads whichever keys each record contains.

Why these words

semi-structured Latin semi-, half, plus Latin structus, piled up, from struere, to build qualifies the head noun, marking the given material as only partly arranged
data Latin data, things given, plural of datum supplies the head noun, the given material the rest of the phrase is naming

Where it came from

Origin: English collocation from Latin semi- (half), Latin structus (piled up, from struere, to build), and Latin data (things given, plural of datum)
Entered the language: 1990s
What changed: Semi- had meant half since Latin. Structure had meant a building, then any arrangement. Data had meant gifts of fact, then the records machines keep. The adjective first described interviews that followed a guide without a fixed script. Database papers in the 1990s joined the three for tagged records without a rigid schema, and the phrase later named a middle band in training pipelines.

How it is spelled

Pattern: semi- is a Latin prefix for half, usually hyphenated before the stem
Pattern: -ure nouns sit beside -ured adjectives
Pattern: Latin struere keeps struc- before t
Pattern: data stays the Latin plural of datum, even when English treats it as a mass noun
Breaks the pattern: the noun phrase stays two words; the hyphen lives inside the first word, not between the two
Breaks the pattern: semi-structured keeps the hyphen; semiconductor and semicircle have gone solid
Breaks the pattern: data looks plural but computing English often treats it as a mass noun

Spelled like

Broken into chunks

What it sits beside

Same subject

Same shape

Data types by shape

Data compounds

Semi- family

Phase 3: Data Fundamentals: Types, Pipelines, and Preparation

Models are only as good as their data — understand the raw material and the engineering that shapes it before covering how it flows or breaks.