Chapter 12 — Metadata and data dictionaries
Lesson map
Lesson 12 published. Map, example, EX034.
flowchart TD
N0["Learning outcomes"]
N1["12.1 Building a dictionary"]
N2["12.2 Resolving meanings"]
N3["12.3 Keeping it current"]
N4["12.4 Using the dictionary"]
N0 --> N1 --> N2 --> N3 --> N4
N4 --> EX["Worked example"]
EX --> Q["Exercise EX034"]
Logical drawing
flowchart LR
N0["Learning outcomes"]
N1["12.1 Building a dictionary"]
N2["12.2 Resolving meanings"]
N3["12.3 Keeping it current"]
N4["12.4 Using the dictionary"]
N0 --> N1 --> N2 --> N3 --> N4 --> Q["EX034"]
[Learning outcomes]
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v
[12.1 Building a dictionary]
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v
[12.2 Resolving meanings]
|
v
[12.3 Keeping it current]
|
v
[12.4 Using the dictionary]
|
v
[Worked example] --> [Exercise EX034]
Learning outcomes
You will (1) build a data dictionary; (2) keep it current; (3) use it to answer questions.
12.1 Building a dictionary
Ravi builds a data dictionary for the repair jobs table. For each field he records the name, plain-language meaning, data type, allowed values or format, whether it is required, the source and the owner. He gathers meanings from the steward and system documentation. Some fields have no documented meaning; he asks staff who use them and records their answers, flagging any where answers differ, such as two meanings for a field named completed flag. The steward reviews each entry before it is published.
12.2 Resolving meanings
The completed flag is set by contractors when work is finished, but call handlers believe it means the tenant has confirmed satisfaction. Reports counting completed jobs mix both interpretations. Ravi brings the question to the steward, who confirms the contractor meaning and asks IT to add a separate field for tenant confirmation. The dictionary records the decision. He notes that dictionaries surface ambiguity that otherwise causes silent errors in reports. Reports are updated to use the contractor meaning, and the new field is added to the dictionary when created.
12.3 Keeping it current
Ravi links the dictionary to the database schema with a script that lists fields in the database and compares them with dictionary entries, flagging fields missing from the dictionary and entries for fields that no longer exist. The script runs weekly. When IT adds a field, the report prompts the steward to document it. He explains that automated comparison prevents dictionaries from drifting out of date, a common reason they are ignored. The steward documents new fields within a week of each report, and missing entries become rare.
12.4 Using the dictionary
Analysts, call handlers and auditors begin using the dictionary to answer questions. When the regulator asks how Calder Valley defines a completed emergency repair, Mrs. Okonjo answers from the dictionary within minutes. Ravi adds a page explaining how to read entries. Ms. Moreau notes that metadata proves its value when people can answer real questions quickly, and that this practical benefit is what keeps owners willing to maintain it. The regulator's reviewer later notes the clarity of the answer, which encourages owners to keep entries up to date.
Worked example
Ravi builds a repair jobs dictionary, resolves conflicting meanings of the completed flag, automates comparison with the schema and sees the dictionary answer a regulator question quickly.
Synthetic case. The dictionary is synthetic.
Errors and limits
Dictionaries without automated checks drift and lose trust.
Exercises
- EX034 — Completed flag meanings. What two meanings did the completed flag have? Rubric: 3 = contractor finished work versus tenant satisfaction;; 2 = both;; 1 = one;; 0 = none.
- EX035 — Drift check. How does Ravi keep the dictionary current? Rubric: 3 = a weekly script comparing schema and entries;; 2 = partly correct;; 1 = vague;; 0 = none.
- EX036 — Regulator answer. What did the dictionary help answer? Rubric: 3 = the definition of a completed emergency repair;; 2 = partly correct;; 1 = vague;; 0 = none.
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