Representation of customizable types in a development environment

A computing system comprising:

• a processor;
• and
• memory storing instructions executable by the processor, wherein the instructions, when executed, configure the computing system to:
• access a type file representing a type in a first version of a computing system, wherein an object model defines a structure of properties and methods that define behavior of a runtime object derived from the type;
• based on application of the object model to a second, customized version of the computing system, identify a customization made to the type in the first version of the computing system to obtain the second, customized version of the computing system;
• serialize the identified customization into a customization file that is separate from the type file and stores a particular element representing the identified customization;
• map the customization file to the type file;
• and
• based on an indication of a request to execute the customized version in a runtime environment:
• access the customization file based on the map,
• de-serialize the customization file into a corresponding object representation of the customization,
• access the type file representing the type, and
• construct the customized version by applying the object representation of the customization to the type in the first version.