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AI-900 Practice Question: Describe features of Natural Language Processing workloads on Azure

What is 'span-based named entity recognition' and how does it differ from sequence labelling?

⚠ Common exam trap

Many candidates confuse 'span' with 'document span' or 'paragraph span' (options A and D) or think it refers to multilingual coverage (option C), when the actual technical distinction is about handling overlapping and nested entities within a single text segment.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

Identifying text spans as candidate entities and classifying each span — handling overlapping and nested entities

Span-based named entity recognition (NER) identifies candidate entities by first locating text spans (contiguous sequences of tokens) and then classifying each span into an entity type. This differs from sequence labeling (e.g., BIO tagging) because it can naturally handle overlapping and nested entities—for example, recognizing both "University of Washington" as an organization and "Washington" as a location within the same sentence—whereas sequence labeling typically assigns a single label per token and struggles with such hierarchies.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • NER that works across spans (paragraphs) of text rather than single sentences

    Why it's wrong here

    This description confuses the text span as a unit of analysis with the broader context of paragraphs. Span-based NER identifies candidate entity phrases within a sentence and classifies each one, whereas paragraph-level processing is about leveraging surrounding context to improve predictions. The key mechanism is extracting and classifying local text spans, not aggregating information across multiple sentences or paragraphs.

  • Identifying text spans as candidate entities and classifying each span — handling overlapping and nested entities

    Why this is correct

    Span-based NER works by enumerating all possible text intervals in a sequence and classifying each candidate span as a named entity type or non-entity. Because every span is scored independently, overlapping and nested entities—such as 'University of Washington' inside a larger organization—are handled naturally, whereas token-level sequence labeling typically assumes flat, non-overlapping entities. This direct span classification is the defining characteristic of the approach.

  • A technique that spans multiple languages to recognise entities in multilingual text

    Why it's wrong here

    This option describes cross-lingual NER, which addresses how well a model transfers entity recognition across different languages, but that is orthogonal to the architectural strategy of span-based NER. Span-based NER is concerned with how entities are extracted and classified from text—by enumerating spans and labeling them—not with the number of languages supported. A span-based model can be monolingual or multilingual; multilingual capability is a separate design consideration.

  • NER that spans multiple documents to track entities across a corpus

    Why it's wrong here

    Tracking the same entity across many documents requires coreference resolution and entity linking to decide whether mentions in different sources refer to the same real-world object. Span-based NER, by contrast, operates locally within a single document: it extracts candidate text spans and assigns entity types, such as person, location, or organization. It does not attempt to connect those entities across a broader corpus, so this definition conflates span-based extraction with cross-document coreference.

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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