Metadata

The zkDatabase metadata system manages essential information for both collections and documents within the database. This metadata ensures that data is structured, accessible, and verifiable, especially in the context of Zero-Knowledge Proofs (ZKPs) used for cryptographic integrity.

Collection Metadata

Collection metadata contains details about a collection, including the name, description, schema, ownership, permissions, and additional attributes such as disk size.

Key Fields in TCollectionMetadata:

1. collectionName: The name of the collection.
2. owner: The owner of the collection.
3. group: The group that share the same permission of the collection.
4. permission: This value is typically a number that encodes all the permissions as a bitmask. The individual bits represent whether specific permissions (e.g., read, write, delete) are enabled or disabled.
5. sizeOnDisk: The size of the collection in the database (MongoDB-specific).
6. schema: Defines the structure of the data within the collection, mapping fields to specific provable types used in zk-SNARKs for data verification.
7. createdAt: Timestamp when the collection was created.
8. updatedAt: Timestamp when the collection was last updated.

Provable Types in Schema:

The schema is an important part of collection metadata, specifying how the fields of a collection should be structured. The fields are mapped to provable types, ensuring that data is compatible with Zero-Knowledge Proofs. A schema is typically defined as an array of TSchemaSerializedFieldDefinition. This array holds multiple field definitions, each specifying the field's name and kind.

[
  {
    name: "age",
    kind: "UInt32",
  },
  {
    name: "isActive",
    kind: "Bool",
  },
  {
    name: "username",
    kind: "CircuitString",
  },
];

Methods for Managing Collection Metadata:

• info(): Retrieves metadata for the collection, including the name, creation and update timestamps, schema, and ownership.
• groupSet(groupName: string): Associates a group with the collection.
• ownerSet(userName: string): Sets or updates the owner of the collection.
• permissionSet(permission: Permission): Sets the permissions for the collection (e.g., read, write, delete).
• permissionGet(): Retrieves the current permissions associated with the collection.

Document Metadata

Document metadata includes detailed information about individual documents within a collection. This metadata is essential for managing document-level attributes, ensuring data integrity, and handling access control.

Key Fields in TDocumentMetadata:

1. collectionName: The name of the collection.
2. docId: The unique identifier for the document.
3. merkleIndex: A Merkle index is the index of the document in a Merkle tree, which is crucial for efficient data retrieval and validation.
4. owner: The owner of the collection.
5. group: The group that share the same permission of the collection.
6. permission: This value is typically a number that encodes all the permissions as a bitmask. The individual bits represent whether specific permissions (e.g., read, write, delete) are enabled or disabled.
7. sizeOnDisk: The size of the collection in the database (MongoDB-specific).
8. schema: Defines the structure of the data within the collection, mapping fields to specific provable types used in zk-SNARKs for data verification.
9. createdAt: Timestamp when the collection was created.
10. updatedAt: Timestamp when the collection was last updated.

Methods for Managing Document Metadata:

• info(): Retrieves the metadata for the document, including its ID, collection name, creation timestamp, and ownership details.
• groupSet(groupName: string): Associates a group with the document.
• ownerSet(userName: string): Sets or updates the owner of the document.
• permissionSet(permission: Permission): Sets the permissions for the document (e.g., read, write, delete).
• permissionGet(): Retrieves the current permissions associated with the document.