This document defines key terms related to reflection such as introspection, intercession, structural reflection, and behavioral reflection. It discusses how reflection allows everything to be represented as an object and that metadata contains information about classes, fields, methods and other aspects that are not compiled into binary code. Reflection is used to build tools and metadata is used outside of source code whenever a class is referenced.

2. Reflection
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 2 / 10

3. Terminology
Introspection—self-representation can be queried.
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 3 / 10

4. Terminology
Introspection—self-representation can be queried.
Intercession—self-representation can be changed.
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 3 / 10

5. Terminology (II)
Structural reflection—concerned with structure.
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 4 / 10

6. Terminology (II)
Structural reflection—concerned with structure.
Behavioral reflection—concerned with execution.
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 4 / 10

7. Reflection in Object Languages
Everything is an object.
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 5 / 10

8. Purpose
Tools.
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 6 / 10

9. Alternative
Source code
Byte code
AST
Custom represenation
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 7 / 10

10. Metadata
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 8 / 10

11. What Is Metadata?
Field and method names
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 9 / 10

12. What Is Metadata?
Field and method names
Class names
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 9 / 10

13. What Is Metadata?
Field and method names
Class names
Various modifiers
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 9 / 10

14. What Is Metadata?
Field and method names
Class names
Various modifiers
Even type information
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 9 / 10

15. What Is Metadata?
Field and method names
Class names
Various modifiers
Even type information
More or less anything that is not compiled into binary
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and Metadata December 14, 2010 9 / 10

16. Is Metadata Used Outside of Source Code?
Yes
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and MetadataDecember 14, 2010 10 / 10

17. Is Metadata Used Outside of Source Code?
Yes
Whenever we are referring to a class we are supplying it with an
additional information
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and MetadataDecember 14, 2010 10 / 10

18. Is Metadata Used Outside of Source Code?
Yes
Whenever we are referring to a class we are supplying it with an
additional information
Why don’t we include metadata in the source code? Is it possible?
Michal P´se (CTU in Prague)
ıˇ Object Programming Lect. 12: Reflection and MetadataDecember 14, 2010 10 / 10