The PDM project contains two top-level packages,
ska_oso_pdm.schemas as shown in the figure below. The
package contains Python object models for the logical entities in the SB
data model. The
ska_oso_pdm.schemas package contains code to transform the
classes defined in
ska_oso_pdm.entities to and from JSON.
The project layout and naming conventions are:
- The SB data model is divided into logical groups that collect related entities together.
- For each SB entity grouping, a corresponding Python module is
ska_oso_pdm.schemas. If the grouping is complex and contains many entities, the modules may be located inside a dedicated package for the group.
- Python classes representing the SB data model entities are found
in the corresponding
- Marshmallow schema to transform
ska_oso_pdm.entitiesobjects to and from JSON are found in
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.
Classes to marshall the
ska_oso_pdm.messages objects to and from JSON are
defined in the
ska_oso_pdm.schemas package. This project uses
Marshmallow for JSON serialisation. Classes
ska_oso_pdm.schemas define Marshmallow schemas which are used by
Marshmallow during JSON conversion.