Mortgage model

Naming is a written law rather than a convention. Types, properties and relationships are lower snake case; abbreviations are spelled out unless expansion is painful; and the property suffix carries the type — an indicator is boolean, an identifier is an identifier, an amount and a percent are decimal, and a type is an enumeration whose range is a named enumeration set backed by its own file.

Definitions are required to be complete sentences that define the term rather than expand the acronym. The stated reason on record is future use by a conversational system: a definition reading as a glossary stub transfers nothing to a model reading it.

Every proposed change ran a fixed sequence: a use case submitted on a form, a draft class diagram, alignment against the existing model, review by a named domain expert, revision, notice to the requester, then publication.

Identity is immutable. Every state of an entity is a new database-generated identifier, and a stable global identifier groups every state of the same real-world thing, named for its class. Reading history is a query over that group rather than an audit table, and a correction never destroys what it corrected.

An attribute becomes its own class on six tests: whether it repeats, whether it is shared, whether it has internal structure, whether it changes over time, whether it relates to other attributes, and how it is used. The tests are what kept the model from either flattening into wide records or exploding into a class per field.

There is a deprecation pipeline for the model itself: duplicate analysis, impact analysis across every consumer of a class, automatic upcasting of a caller's payload to the current model, and usage monitoring of classes on the way out. Several removals were executed through it, each with its own recorded runbook.

Validation is two-layered — see Lexicon for the serving surface. Syntactic shapes constrain datatype, enumeration, pattern, length and range. Semantic shapes carry conditional rules: if a borrower's marital status is married, the spouse's name becomes required.