Possible Formats for .yes document using invoice.yml example.

invoice-A.yes

--- 
/:
  tag: <tag:clarkevans.com,2002:invoice>
invoice: &mandatoryint 
  type: int
  required: true
date:
  type: date
  required: true 
bill-to: &billing-schema-alias 
  type: map 
  required: true
bill-to/given: &amms # Short for "All Mandatory Strings Schema" 
  type: str 
  required: true 
bill-to/family: *amms 
bill-to/address:
  type: map 
  required: true
bill-to/address/lines: *amms 
bill-to/address/city: *amms # Or suburb. 
bill-to/address/state: &aoss # Short for "All Optional Strings Schema" 
  type: string 
  required: false # Not every country has states or provinces. 
bill-to/address/country: &aoss # Unnecessary if posting in the same country. 
bill-to/address/postal: &aoss  # Some countries don't use postcodes. 
ship-to: *billing-schema-alias # Yay for anchors and aliases! 
tax: &currency # Should indicate two decimal places - no more, no less. 
  type: float 
  required: true 
total: *currency 
comments: *amms 
product: 
  type: seqorsing: # See below 
  required: true 
product/sku: *amms 
product/quantity: *mandatoryint 
product/description: *amms 
product/price: *currency 
...

invoice-B.yes

---
/: 
  tag: <tag:clarkevans.com,2002:invoice>
  value:
    invoice: &mandatoryint 
      type: int
      required: true #Shouldn't we use booleans like true and false? 
    date:
      type: datetime #Indicate somehow that dates are required, buttimes are not? 
      required: true 
    bill-to: &billing-schema-alias 
      type: map 
      required: true 
      value: # We could refer to this by Ypaths, but it feels more natural to embed in it the parent structure schema 
        given: &amms # Short for "All Mandatory Strings Schema" 
          type: str 
          required: true 
        family: *amms 
        address:
          type: map 
          required: true 
          value:
            lines: *amms 
            city: *amms # Or suburb. 
            state: &aoss # Short for "All Optional Strings Schema" 
              type: string 
              required: false # Not every country has states or provinces. 
            country: &aoss # Unnecessary if posting in the same country. 
            postal: &aoss # Some countries don't use postcodes. 
    ship-to: *billing-schema-alias # Yay for anchors and aliases! 
    tax: &currency # Should indicate two decimal places - no more, no less. 
      type: float 
      required: true 
    total: *currency 
    comments: *amms 
    product: 
      type: seqorsing: # See below 
      required: true 
      value: 
        sku: *amms 
        quantity: *mandatoryint 
        description: *amms 
        price: *currency 
...

invoice-C.yes

---
/: 
  @tag: <tag:clarkevans.com,2002:invoice>
  invoice: &mandatoryint
    @type: int
    @required: true #Shouldn't we use booleans like true and false? 
  date:
    @type: datetime #Indicate somehow that dates are required, buttimes are not? 
    @required: true 
  bill-to: &billing-schema-alias 
    @type: map 
    @required: true 
    given: &amms # Short for "All Mandatory Strings Schema" 
      @type: str 
      @required: true 
    family: *amms 
    address:
      @type: map 
      @required: true 
    lines: *amms 
    city: *amms # Or suburb. 
    state: &aoss # Short for "All Optional Strings Schema" 
      @type: string 
      @required: false # Not every country has states or provinces. 
    country: &aoss # Unnecessary if posting in the same country. 
    postal: &aoss # Some countries don't use postcodes. 
  ship-to: *billing-schema-alias # Yay for anchors and aliases! 
  tax: &currency # Should indicate two decimal places - no more, no less. 
    @type: float 
    @required: true 
  total: *currency 
  comments: *amms 
  product: 
    @type: seqorsing: # See below 
    @required: true 
    sku: *amms 
    quantity: *mandatoryint 
    description: *amms 
    price: *currency 
...