commit 7f32213c86fc0f254585d317406c397dcf0ff5d3
Author: Skylar Ittner <skylar@netsyms.com>
Date:   Sat Nov 25 23:46:36 2023 -0700

    Add 'Specification'

diff --git a/Specification.md b/Specification.md
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+## Basic Rules
+
+* The barcode shall be in QR Code, DataMatrix, or PDF417 format.
+* Data fields shall be delineated with a pipe character (`|`).
+* Data shall be encoded as ASCII or UTF-8. If the chosen barcode format has a different default/preferred encoding, that encoding may be used instead.
+* Data fields shall not include a pipe character or newline.
+* The data must not start or end with a pipe character.
+* Most fields are not strictly required and may be left empty when not needed. Implementations may reject a code with insufficient data.
+
+## Data Header
+
+All barcodes shall start with `QSv1` as the first field. The second field shall specify the subtype of the barcode.
+
+### Subtypes
+
+* `tofrom`: Destination and return addresses only.
+* `full`: Same as `tofrom` but with additional fields for the package's characteristics and requested extra services.
+
+## Data Fields
+
+### `tofrom`
+
+Position | Meaning
+0 | Format header (`QSv1`)
+1 | Type header (`tofrom`)
+2 | Sender/payer account number (vendor/implementation specific)
+3 | To name
+4 | To company/firm/business
+5 | To street
+6 | To secondary address line
+7 | To city
+8 | To state/province/etc
+9 | To postal code
+10 | To country (ISO 2-character country code)
+11 | To phone
+12 | To email
+13 | From name
+14 | From company/firm/business
+15 | From street
+16 | From secondary address line
+17 | From city
+18 | From state
+19 | From postal code
+20 | From country (ISO 2-character country code)
+21 | From phone
+22 | From email
+
+
+### `full`
+
+Position | Meaning
+0 - 22 | See `tofrom`
+23 | Weight (U.S. ounces)
+24 | Item type (see appendix)
+25 | Length (inches)
+26 | Width (inches)
+27 | Height (inches)
+28 | Non-machinable: `1` if true, otherwise empty
+29 | Certified Mail: `1` if true, otherwise empty
+30 | Registered Mail: `1` if true, otherwise empty
+31 | Registered Mail declared value, USD
+32 | Return Receipt Requested: `1` if true, otherwise empty
+33 | Special rate eligibility: `M` for Media Mail, `L` for Library Mail, empty if not claiming eligibility
+34 | Insurance amount, USD
+35 | Signature services. 1: Signature required, 2: Adult signature required, 3: Restricted delivery signature, 4: Adult restricted signature, 5: Indirect signature.
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