# classify - is this the kind of document expected
Source: https://truecopy.dev/docs/classify/
Module: truecopy/classify

A statement quoting the word invoice in a transaction label must not be filed as an invoice. Precedence, stated rather than smuggled into an ordering.

A bank statement quotes the word _invoice_ in a transaction label. Read in the wrong order it is filed as an invoice, and **every operation it carries leaves the budget with it**.

An IBAN, or the debit/credit/balance vocabulary, settles the question before the word invoice is even looked at.

```ts
import { classifyDocument, type DocumentKind } from 'truecopy/classify';

const KINDS: DocumentKind<'statement' | 'invoice'>[] = [
  {
    name: 'statement',
    requires: [{ anyOf: [{ all: [IBAN] }, { all: [DEBIT, CREDIT] }] }]
  },
  {
    name: 'invoice',
    requires: [{ anyOf: [{ all: [INVOICE_WORDS] }], absent: [IBAN] }]
  }
];

classifyDocument(text, KINDS); // 'statement' | 'invoice' | null
```

## Three notions, and no more

|                 |                                                                                          |
| --------------- | ---------------------------------------------------------------------------------------- |
| **pattern set** | `{ all: [...], occurrences?: n }`: all of its patterns, optionally several times         |
| **requirement** | `{ anyOf: [...sets], absent?: [...] }`: any one of its sets, and none of the absent ones |
| **kind**        | all of its requirements. **First match wins.**                                           |

`absent` is what makes precedence **stated** rather than smuggled into an ordering that means something else. _An invoice only when there is no IBAN_ is written down, in the kind itself, where somebody reading it a year later will find it.

## occurrences: one may be a quotation

```ts
{ all: [PENSION_VOCABULARY], occurrences: 2 }
```

A newspaper article about pensions mentions quarters, carries years and amounts, and would satisfy every other rule. A real record carries the vocabulary dozens of times.

One occurrence may be a citation. Two rarely are.

## This is not the schema question

`classify` asks _is this the kind of document expected at all_. [`schema`](https://truecopy.dev/docs/schema/) asks _does this reading carry what it must_. Two answers to one question always end up disagreeing, so they are two functions and the kind is asked first: a document of the wrong kind deserves no remark about its missing fields.

## Patterns as data

The patterns here are regular expressions, and everything that varies by market, by issuer or by document family should be a **value** rather than a branch; see [pattern](https://truecopy.dev/docs/pattern/). A value can be served by a backend, refined by whoever reads the documents, versioned, and swapped for another market without a deploy. A branch can only be changed by whoever can change the code.

Map of this site for a model: https://truecopy.dev/llms.txt
Every page in one file: https://truecopy.dev/llms-full.txt