User:Swpb/principles

Modeling principles

These are some general principles that should always be followed when modeling on Wikidata. Some come from official guidance, some don't. All represent common mistakes.

Re: qualifiers

1. Qualifiers apply to the main statement or statement value, not to other qualifiers (which can be ambiguous), and their order on a statement should not matter.
2. Restrictive qualifiers (see list) should not appear on basic membership statements or with other transitive properties, as this creates false inferences.
3. Fixed (i.e. universally true) relationships between two items should be expressed with main statements on one or both of those items, and not with qualifiers on other items where one of the items is a statement value, as this is redundant.
4. Look for more specific properties and values that enable information to be expressed without qualifiers, where possible. This simplifies the modeling and makes querying easier.

Other principles

1. Every item should have at least one instance of (P31) or subclass of (P279) statement, as every item is and instance or subclass of something.
2. Statements should appear only on the highest-level subclass over which they universally apply (or sometimes higher, with restrictive qualification). Repeating statements at lower levels is redundant.
3. Deprecation is for statements that were never accurate, not just no longer accurate.