Project layout


This page is out of date and references the old architecture of entity classes and separate Marshmallow schema. This page will be updated to reflect the new architecture which makes use of Pydantic. Once complete, this warning will be removed.

The PDM project contains one top-level package, ska_oso_pdm.entities The ska_oso_pdm.entities package contains Python object models for the logical entities in the Project Data Model (PDM). These classes are Pydantic data models that inherit from PdmEntity.


Project layout and naming conventions.

The project layout and naming conventions are:

  • The package ska_oso_pdm.entities.shared is the lowest-level of the data model and contains basic components that are imported and re-used throughout the project.

  • The SB data model is divided into logical groups that collect related entities together.

  • For each SB entity grouping, a corresponding Python module is created in ska_oso_pdm.entities. If the grouping is complex and contains many entities, the modules may be located inside a dedicated package for the group.

  • The package ska_oso_pdm.entities.common is the highest-level of the the data model and contains complex entities that are common between both MID and LOW telescopes.

Entities overview


Overview of PDM entities

The Python object model for the entities defined in the SB data model are located in the ska_oso_pdm.entities package. In general, each SB entity is represented as a Python class and each entity attribute presented as a class attribute or property.

PDM attributes can be typed as plain Python data types (strings, floats, etc.) or, where appropriate, represented by rich objects if this provides additional value to the client. For example, while astronomical coordinates are represented by floats and strings in the JSON schema, in the object model they are defined as Astropy SkyCoord instances to ensure ensure correct coordinate handling and permit easier manipulation downstream. Similarly, quantities with units could be defined as instances of Astropy Quantity to provide additional functionality.

For details on the entities modelled by this library, see the pages within the API documentation.