Metadata

CROSS Metadata

The CROSS metadata are the metadata standard defined for CrossContracts. They are compliant with the DCAT-CH v.2 vocabulary which itself is compliant with DCAT-AC.

to be updated

The current CROSS metadata include

Attribute	Type	Required	Description
name	str	Yes	Unique identifier for the data contract
title	str	Yes	A human-readable title for the data. Think of this as the label that will be used in graphs and tables.
description	str	Yes	A human-readable description of the data. This should explain what the data contain. It gives the data a semantic meaning.
tags	list[str]	No	A list of tags that can be used to categorize the table. Defaults to an empty list.

Custom Metadata

This package allow to define your own metadata standard for contracts. The implementation of your own standard is simple and comes in two steps:

1. Create a class that defines your metadata standard
2. Create a contract based on your metadata standard.

Create your metadata standard

To create your own standard, create a class that inherits from the BaseMetaData class. The BaseMetaData is a pydantic model that defines only attribute, i.e., metadata entry, that must be implemented by all contract: the name attribute.

from crosscontract.contracts.contracts import BaseMetaData

class MyMetaData(BaseMetaData):
    """My MetaData standard. The name attribute is already inherited from
    BaseMetaData
    """

    description: str
    owner: str

Create your contract

In the second step you create your contract class that inherits from BaseContract and your created MyMetaData class. While the metadata class determines the metadata, the basic contract class enforces the frictionless schema and provides the validation functionalities:

from crosscontract.contracts import BaseContract

class MyContract(BaseContract, MyMetaData):
    """A custom contract blueprint with custom metadata"""
    pass

That's it. You now have an contract blueprint MyContract that enforces that each contract must have a name, description, and owner attribute and, in addition, a tableschema entry that enforces the frictionless table schema.