What we are building

An agreement you can inspect in six useful ways: meanings, data descriptions, topics, choices, resources and relationships.

Three ink-drawn panels show two property professionals questioning a closed door, comparing an inspection report and floor plan, and annotating a draft while retaining both sources and an unresolved alternative.

Not just another list of field names

We are agreeing what information means: which things it describes, how they connect, which words people use and what conditions matter. You can inspect that agreement through definitions, data descriptions, agreed choices and diagrams. You do not need to write ontology code to say that a definition excludes a normal case or that an important distinction is missing.

OPDA's working-group approach calls for six aligned content outputs. Think of them as six ways of asking a question about one semantic package, not six competing standards. A glossary may explain an inspection; a dictionary may explain a date used in its report; a relationship definition explains how the report connects to the inspection. Each does a different job.

Meaning and data description

Start with the difference between explaining an idea and describing a data element. The glossary tells a reviewer what an inspection means here. The dictionary tells a recipient exactly which date a report element carries. Neither answer can safely be inferred from the word “survey”.

Business glossary · Inspection

Definition: An examination of an identified dwelling during an identified visit, within the scope agreed for that visit.
Purpose: Distinguish the examination from the documents that describe it.
Scope in this package: A visit concerning one dwelling. This teaching definition does not cover every possible kind of inspection.
Ordinary example: The visit to examine Flat 1 at Harbour Court on 12 August 2026.
Counterexample: Correcting wording in the report without another examination is not another inspection.
Review responsibility: In a real package, name the context responsible for the definition and record the evidence and review status.

Data dictionary · Report issue date

Meaning: The calendar date on which the identified report version was issued.
Subject: A particular report version, not the dwelling or inspection.
Expected value: A calendar date whose source can be identified.
Do not substitute: The inspection date, a system's recording date or the period during which a claim applies.

Separate teaching record

Report version 2 · issue date 20 August 2026 · source: the fictional report's version statement.

The example value is not part of the dictionary element's definition. If a later report is issued in September, the value changes but the meaning of “report issue date” need not. A useful review asks both “is the definition clear?” and “does this record actually use it that way?”

Organising topics and recording choices

A topic hierarchy helps people find related concepts. A controlled vocabulary supplies defined terms for a stated use; it can supply a closed set of choices when the scope warrants one. A hierarchy and a choice list are not interchangeable, even when both are displayed as indented words on a screen.

Topic taxonomy · Inspection subjects

Building fabric
- Roof condition
- External wall condition

In this fictional topic scheme, Roof condition is a narrower inspection topic beneath Building fabric.

This organises subjects people discuss. It does not say that a roof-condition topic is a physical part of a building, or that every narrower topic is a kind of its broader topic.

Controlled vocabulary · Physical access outcome

Scope: physical access to a nonempty, identified set of agreed inspection areas during this visit.

All agreed areas: Every area in that set was physically accessed.
Some, but not all, agreed areas: At least one area was accessed and at least one was not.
None of the agreed areas: No area in that set was physically accessed.

With that scope and sufficient evidence, exactly one outcome applies. An empty set is excluded so that “all” and “none” cannot describe the same case.

Suppose the agreed areas are the living room, bedroom and enclosed area. The first two were accessed; the enclosed area was locked. “Some, but not all” fits. If the record contains no access evidence, “none” does not follow: no record of access is not a record of no access. Nor does this list say who may receive the resulting report. Physical access and permission to receive data answer different questions.

What can be described, and how it connects

A resource is something we identify and say things about. It can be a dwelling, an event or a document, not only a physical object. A resource definition explains what sort of subject the model needs to describe. A relationship definition explains a particular connection between subjects.

Resource definition · Inspection

What it defines: The kind of identifiable examination event described by this package's glossary definition.
What we describe about one: Which dwelling it concerns, its agreed scope and when it occurred.
Identity question: Are two records describing the same examination during the same visit, or a separate examination? The answer needs evidence, not just matching dates.
Distinction to preserve: A new report version need not mean a new inspection.

Separate teaching instance

The examination of Flat 1 at Harbour Court on 12 August 2026 is an inspection under this definition. It is one particular event, not the definition itself.

Relationship definition · Describes

Starting subject: A particular report version.
Connected subject: The inspection whose examination it reports.
Meaning in this package: The report version gives an account of that inspection.
Limit: This connection does not establish that every statement in the report is true, or that the report describes every inspection at the dwelling.

Separate teaching statement

Report version 2 describes the 12 August inspection.

Report version 1 also describes that inspection. Both reports can connect to one event without becoming the same document version.

“This event is an Inspection” places an example in the defined class. “This report describes this event” connects two particular subjects. Those statements do different work. A website page defining an Inspection class is therefore not evidence of a store of live inspection records. Keep this distinction when you later read a real candidate page.

The formal ontology expresses the agreement for machine use. JSON-LD is one generated delivery artefact from it. The human-readable views should remain aligned with that agreement, rather than acquiring their own competing meanings.

Practice · Which view answers the question?

Choose a starting specimen for each question before comparing your reasoning with the visible responses.

Six questions, six useful starting points
Question	Worked response
Does correcting a report count as another inspection?	The glossary gives the scope and counterexample: a wording correction alone is excluded.
Whose date is 20 August?	The dictionary attaches the issue date to report version 2.
Under which broader topic would I find roof condition?	The topic taxonomy places it under Building fabric.
Which outcome records access to two of three agreed areas?	The controlled vocabulary defines “Some, but not all”.
What evidence would distinguish two inspection events?	The resource definition identifies the identity question; particular records supply the evidence.
What does the word “describes” connect?	The relationship definition names its report-version starting point and inspection target.

These are starting points, not closed compartments. Reviewing the glossary's counterexample may reveal a relationship or dictionary element that also needs clarification.

Practice · Change a label, a meaning or an example?

A reviewer proposes “date of report issue” as an alternative label for “report issue date”. Another proposes using that element for the inspection's occurrence date. A third changes a teaching example to describe Flat 2. Do all three proposals change the agreement in the same way?

Worked response

The first is a label proposal: the intended subject and meaning remain the same. Check that readers understand the alternative and that labels stay consistent where reused. The second changes meaning. Test the dictionary, examples, affected relationships and requirements against the new subject; simply relabelling old values would be misleading.

The third changes a particular example's subject. It does not, by itself, change the definition of Inspection. It still needs a coherent example: if its source describes Flat 1, changing only the heading to Flat 2 creates an unsupported account. None of these changes automatically alters the roof-topic taxonomy. Review the affected views, and say why the others can remain unchanged.

A useful review note identifies the question, the relevant specimen and the consequence of the proposed change. The output's name is useful because it helps someone find the agreement—not because remembering six names is the point of the work.