In sum, the paper proposes three design principles for how to implement
Background: metaprogramming in OOP
See also
A metaobject is an object that manipulates objects (including itself!). It can change an object’s type, interface, class, methods, attributes, …
The metaobject protocol (MOP) provides the vocabulary to access and manipulate objects. Functions of an MOP include:
- Creating/deleting new classes
- Creating new properties/methods
- Do inheritance
- Generate/change code defining methods of a class
Different implementations of a metaobject protocol can allow for different behaviors when a class is created. For example, if you want a hash table or non-hash table representation of a class, you can use different MOPs.
Mirror-based APIs
In Java, reflection methods are inherent to Class. In JDI (Java Debugging Interface), they make reflection items (Class, Method, etc.) interfaces, allowing for different concrete representations of the reflected items for e.g., different platforms. Benefits:
- Encapsulation. Meta-level facilities encapsulate their implementation
- Stratification. Meta-level facilities are separated out, e.g., to minimize bin size.
- Structural correspondence. Every language construct is mirrored, including things like modules, import/export statements, statements, …