Contract Documents

Contract Document Overview

The documents object defines each type of document in the data contract. At a minimum, a document must consist of 1 or more properties. The additionalProperties properties keyword must be included as described in the constraints section and each property must be assigned a position.

The following example shows a minimal documents object defining a single document (note) with one property (message).

{
  "note": {
    "type": "object",
    "properties": {
      "message": {
        "type": "string",
        "position": 0
      }
    },
    "additionalProperties": false
  }
}

Documents may also define indices, a list of required or transient properties, and a custom configuration. Refer to this table for a brief description of the major document sections:

Feature	Description
Configuration	Document-level settings affecting behavior such as mutability, deletion, and transferability
Properties	Definitions and constraints for each field within a document
Indices	Definitions for indexing document fields to support efficient querying

Document Properties

The properties object defines each field that a document will use. Each field consists of an object that, at a minimum, must define its data type (string, number, integer, boolean, array, object).

Fields may also apply a variety of optional JSON Schema constraints related to the format, range, length, etc. of the data. A full explanation of JSON Schema capabilities is beyond the scope of this document. For more information regarding its data types and the constraints that can be applied, please refer to the JSON Schema reference documentation.

Assigning Position

Each property in a level must be assigned a unique position value, with ordering starting at zero and incrementing with each property. When using nested objects, position counting resets to zero for each level. This structure supports backward compatibility in data contracts by ensuring consistent ordering for serialization and deserialization processes.

Object Properties

The object type cannot be an empty object but must have one or more defined properties. For example, the body property shown below is an object containing a single string property (objectProperty):

const contractDocuments = {
  message: {
    type: "object",
    properties: {
      body: {
        type: "object",
        position: 0,
        properties: {
          objectProperty: {
            type: "string",
            "position": 0
          },
        },
        additionalProperties: false,
      },
      header: {
        type: "string",
        "position": 1
      }
    },
    additionalProperties: false
  }
};

Required Properties

Each document may have some fields that are required for the document to be valid and other fields that are optional. Required fields are defined via the required array, which consists of a list of the field names from the document that must be present. Exclude the required object for documents without required properties.

"required": [
  "<field name a>",
  "<field name b>"
]

Example
The following example (excerpt from the DPNS contract's domain document) demonstrates a document with required fields:

"required": [
  "$createdAt",
  "$updatedAt",
  "$transferredAt",
  "label",
  "normalizedLabel",
  "normalizedParentDomainName",
  "preorderSalt",
  "records",
  "subdomainRules"
]

Transient Properties

Each document may have transient fields that require validation but do not need to be stored by the system once validated. Transient fields are defined in the transient array. Only include the transient object for documents with at least one transient property.

Example

The following example (from the DPNS contract's domain document) demonstrates a document that has 1 transient field:

    "transient": [
      "preorderSalt"
    ]

Property Constraints

There are a variety of constraints currently defined for performance and security reasons.

Description	Value
Minimum number of properties	1
Maximum number of properties	100
Minimum property name length	1
Maximum property name length	64
Property name characters	Alphanumeric (`A-Z`, `a-z`, `0-9`) Hyphen (`-`) Underscore (`_`)

Document Indices

Document indices may be defined if indexing on document fields is required. The indices object should only be included for documents with at least one index.

The indices array consists of one or more objects that each contain:

A unique name for the index
A properties array composed of a <field name: sort order> object for each document field that is part of the index

:::{admonition} Compound Indices :class: attention When defining an index with multiple properties, the ordering of properties is important. Refer to the mongoDB documentation for details. Dash uses GroveDB, which works similarly but requires listing all the index's fields in query order by statements. :::
An optional unique element that determines if duplicate values are allowed for the document
An optional nullSearchable element that indicates whether the index allows searching for NULL values. If nullSearchable is false (default: true) and all properties of the index are null then no reference is added.
An optional contested element that determines if duplicate values are allowed for the document

"indices": [
  {
    "name": "<index name a>",
    "properties": [
      { "<field name a>": "<asc"|"desc>" },
      { "<field name b>": "<asc"|"desc>" }
    ],
    "unique": true|false,
    "nullSearchable": true|false,
    "contested": {
      "fieldMatches": [
        {
          "field": "<field name a>",
          "regexPattern": "<regex>"
        }
      ],
      "resolution": 0
    }
  },
  {
    "name": "<index name b>",
    "properties": [
      { "<field name c>": "<asc"|"desc>" },
    ],
  }
]

Contested Indices

Contested unique indices provide a way for multiple identities to compete for ownership when a new document field matches a predefined pattern. This system enables fair distribution of valuable documents, such as premium DPNS names, through community-driven decision-making.

A two week contest begins when a match occurs. For the first week, additional contenders can join by paying a fee of 0.2 Dash. During this period, masternodes and evonodes vote on the outcome. The contest can result in the awarding of the document to the winner, a locked vote where no document is awarded, or potentially a restart of the contest if specific conditions are met.

The table below describes the properties used to configure a contested index:

Property Name	Type	Description
fieldMatches	array	Array containing conditions to check
fieldMatches.field	string	Name of the field to check for matches
fieldMatches.regexPattern	string	Regex used to check for matches
resolution	integer	Method to resolve the contest: `0` - masternode voting

Example

This example (from the DPNS contract's domain document) demonstrates the use of a contested index:

"contested": {
  "fieldMatches": [
    {
      "field": "normalizedLabel",
      "regexPattern": "^[a-zA-Z01-]{3,19}$"
    }
  ],
  "resolution": 0,
  "description": "If the normalized label part of this index is less than 20 characters (all alphabet a-z, A-Z, 0, 1, and -) then a masternode vote contest takes place to give out the name"
}

Index Constraints

For performance and security reasons, indices have the following constraints. These constraints are subject to change over time.

Description	Value
Minimum/maximum length of index `name`	1 / 32
Maximum number of indices	10
Maximum number of unique indices	10
Maximum number of contested indices	1
Maximum number of properties in a single index	10
Maximum length of indexed string property	63
Usage of `$id` in an index disallowed	N/A
Note: Dash Platform does not allow indices for arrays. Maximum length of indexed byte array property	255
Note: Dash Platform does not allow indices for arrays. Maximum number of indexed array items	1024

Example
The following example (excerpt from the DPNS contract's preorder document) creates an index named saltedHash on the saltedDomainHash property that also enforces uniqueness across all documents of that type:

"indices": [
  {
    "name": "saltedHash",
    "properties": [
      {
        "saltedDomainHash": "asc"
      }
    ],
    "unique": true
  }
]

Document Configuration

Documents support the following configuration options to provide flexibility in contract design. Only include configuration options in a data contract when using non-default values.

Document option	Type	Description
`documentsKeepHistory`	boolean	If true, documents keep a history of all changes. Default: false.
`documentsMutable`	boolean	If true, documents are mutable. Default: true.
`canBeDeleted`	boolean	If true, documents can be deleted. Default: true.
`transferable`	integer	Transferable without a marketplace sell: `0` - Never `1` - Always See the NFT page for more details
`tradeMode`	integer	Built-in marketplace system: `0` - None `1` - Direct purchase (the purchaser can buy the item without requiring approval) See the NFT page for more details
`creationRestrictionMode`	integer	Restriction of document creation: `0` - No restrictions `1` - Contract owner only `2` - No creation (System Only) See the NFT page for more details

Security option	Type	Description
`requiresIdentity` `EncryptionBoundedKey`	integer	Key requirements for identity encryption: `0` - Unique non-replaceable `1` - Multiple `2` - Multiple with reference to latest key
`requiresIdentity` `DecryptionBoundedKey`	integer	Key requirements for identity decryption: `0` - Unique non-replaceable `1` - Multiple `2` - Multiple with reference to latest key
`signatureSecurity` `LevelRequirement`	integer	Public key security level: `1` - Critical `2` - High `3` - Medium. Default is High if none specified.

:::{dropdown} List of all usable document properties

This list of properties is defined in the Rust DPP implementation and the document meta-schema.

Property Name	Type	Description
`type`	string	Specifies the type of the document, constrained to "object".
`$schema`	string	The schema URL reference for the document.
`$defs`	object	References the `documentProperties` definition.
`indices`	array	Defines indices for the document with properties like `name`, `unique`, `nullSearchable`, and `contested`.
`signatureSecurity` `LevelRequirement`	integer	Public key security level: `1` - Critical `2` - High `3` - Medium. Default is High if none specified.
`documentsKeepHistory`	boolean	If true, documents keep a history of all changes. Default: false.
`documentsMutable`	boolean	If true, documents are mutable. Default: true.
`canBeDeleted`	boolean	If true, documents can be deleted. Default: true.
`transferable`	integer	Transferable without a marketplace sell: `0` - Never `1` - Always
`tradeMode`	integer	Built-in marketplace system: `0` - None `1` - Direct purchase (the purchaser can buy the item without requiring approval)
`creationRestrictionMode`	integer	Restriction of document creation: `0` - No restrictions `1` - Contract owner only `2` - No creation (System Only).
`requiresIdentity` `EncryptionBoundedKey`	integer	Key requirements for identity encryption: `0` - Unique non-replaceable `1` - Multiple `2` - Multiple with reference to latest key
`requiresIdentity` `DecryptionBoundedKey`	integer	Key requirements for identity decryption: `0` - Unique non-replaceable `1` - Multiple `2` - Multiple with reference to latest key
`properties`	object	Defines the properties of the document.
`transient`	array	An array of strings specifying transient properties that are validated by Platform but not stored.
`additionalProperties`	boolean	Specifies whether additional properties are allowed. Must be set to false, meaning no additional properties are allowed beyond those defined.

:::

Example

The following example (from the DPNS contract's domain document) demonstrates the use of several configuration options:

{
  "domain": {
    "documentsMutable": false,
    "canBeDeleted": true,
    "transferable": 1,
    "tradeMode": 1,
    "..."
  }
}

Keyword Constraints

There are a variety of keyword constraints currently defined for performance and security reasons. The following constraints apply to document definitions. Unless otherwise noted, these constraints are defined in the platform's JSON Schema rules (e.g., rs-dpp document meta schema).

Keyword	Constraint
`default`	Restricted - cannot be used (defined in DPP logic)
`propertyNames`	Restricted - cannot be used (defined in DPP logic)
`uniqueItems: true`	`maxItems` must be defined (maximum: 100000)
`pattern: <something>`	`maxLength` must be defined (maximum: 50000)
`format: <something>`	`maxLength` must be defined (maximum: 50000)
`$ref: <something>`	Disabled `$ref` can only reference `$defs`. Remote references not supported.
`if`, `then`, `else`, `allOf`, `anyOf`, `oneOf`, `not`	Disabled for data contracts
`dependencies`	Not supported. Use `dependentRequired` and `dependentSchema` instead
`additionalItems`	Not supported. Use `items: false` and `prefixItems` instead
`patternProperties`	Restricted - cannot be used for data contracts
`pattern`	Accept only RE2 compatible regular expressions (defined in DPP logic)

Example Syntax

This example syntax shows the structure of a documents object that defines two documents, an index, and a required field.

{
  "<document name a>": {
    "type": "object",
    "properties": {
      "<field name b>": {
        "type": "<field data type>",
        "position": "<number>"
      },
      "<field name c>": {
        "type": "<field data type>",
        "position": "<number>"
      },
    },
    "indices": [
      {
        "name": "<index name>",
        "properties": [
          {
            "<field name c>": "asc"
          }
        ],
        "unique": true|false
      },
    ],
    "required": [
      "<field name c>"
    ],
    "additionalProperties": false
  },
  "<document name x>": {
    "type": "object",
    "properties": {
      "<property name y>": {
        "type": "<property data type>",
        "position": "<number>"
      },
      "<property name z>": {
        "type": "<property data type>",
        "position": "<number>"
      },
    },
    "additionalProperties": false
  },    
}

Document Schema

See full document schema details in the rs-dpp document meta schema.

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Contract Documents

Contract Document Overview

Document Properties

Assigning Position

Object Properties

Required Properties

Transient Properties

Property Constraints

Document Indices

Contested Indices

Index Constraints

Document Configuration

Keyword Constraints

Example Syntax

Document Schema

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Contract Documents

Contract Document Overview

Document Properties

Assigning Position

Object Properties

Required Properties

Transient Properties

Property Constraints

Document Indices

Contested Indices

Index Constraints

Document Configuration

Keyword Constraints

Example Syntax

Document Schema