DP-900 Describe core data concepts Practice Question
A hospital collects patient data from multiple sources. Source A stores patient vitals as a continuous stream of readings from wearable devices. Source B stores historical medical records in a relational database with fixed columns (PatientID, Diagnosis, AdmissionDate). Source C stores doctor's notes as unstructured text files. Which statement correctly describes the structure of data from these sources?
⚠ Common exam trap
Candidates often confuse a continuous data stream (Source A) with semi-structured data, but in DP-900, a stream of fixed-format sensor readings is considered structured because it has a consistent schema (e.g., timestamp and numeric values), not because it arrives in real time.
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
✓
Source A is structured, Source B is structured, Source C is unstructured.
Source A stores patient vitals as a continuous stream from wearable devices, which is structured data because it typically consists of time-stamped numeric readings with a fixed schema (e.g., timestamp, heart rate, blood pressure). Source B uses a relational database with fixed columns (PatientID, Diagnosis, AdmissionDate), which is classic structured data. Source C contains unstructured text files (doctor's notes) with no predefined schema. Therefore, Option B correctly identifies all three sources.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Source A is semi-structured, Source B is structured, Source C is unstructured.
Why it's wrong here
Source B and C are correctly labeled, but Source A is misclassified. A continuous stream of vital-sign readings normally has a fixed schema — device ID, timestamp, measurement type, numeric value, and unit — so every event fits the same columns and can be loaded directly into a relational table. Semi-structured data such as JSON or XML allows fields to vary from record to record, which does not describe this stream. Therefore Source A is structured, making the entire option incorrect.
- ✓
Source A is structured, Source B is structured, Source C is unstructured.
Why this is correct
All three classifications are accurate. Source A is structured because each vital-sign reading is a row with the same columns, such as patient ID, timestamp, sensor type, and measured value, making it directly queryable as a table. Source B is structured because it lives in a relational database where tables enforce rows and columns. Source C is unstructured because free-text clinical notes do not have a predefined data model or fixed fields, even though they may contain useful information for analysis.
- ✗
Source A is structured, Source B is unstructured, Source C is semi-structured.
Why it's wrong here
Source A is correctly identified as structured, but the classification of the other two is reversed. Historical medical records stored in a relational database are structured because the schema of tables, primary keys, and data types is fixed. Doctor's notes as plain text files are unstructured because they consist of free-form prose with no enforced fields, tags, or metadata; semi-structured data like JSON would have a flexible but detectable organization. Hence this option is wrong for B and C.
- ✗
Source A is semi-structured, Source B is semi-structured, Source C is unstructured.
Why it's wrong here
While Source C is correctly called unstructured, both prior sources are misclassified. The monitor stream's records all adhere to a uniform set of columns, and the relational medical records are managed under a strict predefined schema, so neither has the self-describing, field-varying nature of semi-structured data such as JSON documents or XML files. Semi-structured data typically carries headers or tags and allows some records to lack fields that others have, which does not match either source. Therefore this option mislabels Source A and Source B as semi-structured.
Go deeper
Related to this question
Learn chapter
Data Roles and Core Concepts
Key term
Relational database
A relational database organizes data into tables with rows and columns, where each table relates to others using unique keys, allowing efficient storage, retrieval, and manipulation of structured information.
Key term
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
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