README.md

Uniform Data Access Layer

This is the Python specification of the Uniform Data Access Layer (UDAL).

Documentation: https://lab.fairease.eu/udal/

Quick Start

There are two sides to a UDAL implementation:

• the user
• the implementer

A user can find existing UDAL implementations that support the named queries they need. An implementer can provide a package that is able to execute a set of named queries for their data or for data from third parties.

Use an existing implementation

Use an existing UDAL implementation, assuming an existing module my.udal with an implementation MyUDAL, supporting a named query urn:example.com:example:

from my.udal import MyUDAL as UDAL

print(UDAL().execute('urn:example.com:example').data())

Create a new implementation

Create a new UDAL implementation that can be used as above:

import udal.specification as udal

class MyResult(udal.Result[str]):
    """A result containing a string."""

    def data(self, type: type[str] | None = None):
        if type is None or type is str:
            return self._data
        else:
            raise Exception(f'cannot return the data as {type}')

class MyUDAL(udal.UDAL):

    def __init__(self):
        pass

    @property
    def query_names(self):
        return ['urn:example.com:example']

    @property
    def queries(self):
        return {
            'urn:example.com:example': udal.NamedQueryInfo('urn:example.com:example', {})
        }

    def execute(self, name, params={}):
        match name:
            case 'urn:example.com:example':
                return MyResult(self.queries[name], 'example data')
            case _:
                raise Exception(f'query "{name}" not supported')