I am working on developing a UML class diagram from C++ code.  I have a classless header file that is basically a definitions file (it has structs, enums and defined constants).  I know how to represent structs and enums in general, but I am unclear about how to represent (or if I should represent) constants in the class diagram.  Additionally I am curious if the structs, enums and constants should be part of some larger container? (Like referencing the namespace helper or the definitions.h)#ifndef DEFINITIONS_H#define DEFINITIONS_H#include <stdint.h>#include <string>namespace helper{  enum Colors  {    Red = 0,    Blue,    Green     };  struct volunteer  {    std::string FirstName;    std::string MiddleName;    std::string LastName;    std::string Occupation;  };  typedef const std::string Constant;  Constant Foo = Foo;  Constant Bar = Bar;  Constant Bat = Bat; }#endif
How to represent constants in UML class diagram?
c++;uml;class diagram;headers
The goal of a class diagram is to document relationships between classes as well as how objects of those classes can change:In software engineering, a class diagram in the Unified Modeling  Language (UML) is a type of static structure diagram that describes  the structure of a system by showing the system's classes, their  attributes, operations (or methods), and the relationships among  objects.Source: WikipediaThe key elements here are:Relationships between classes: given a class, what other classes does it use?Operations that can be performed on a class: what methods/functions belong to a class?State belonging to a class: what data does a class encapsulate?A constant does not fit into any of these elements. It is not a relationship, and certainly not an operation. The closest element is state, but a constant is pretty much the opposite: it is static, and not tied to an object. While a class diagram documents classes, it is focused on elements of classes used by objects of those class types.In your specific example, I would do the following:The enum would be a class in the diagram, but would likely be empty. The only state is the integer that represents each enum value, but that is essentially a surrogate key and not referenced in code. Note that if you use a C++ enum class instead, you might have state worth documenting.The struct should be a class with no behavior, but the state documented as public.Those constants should not be documented in a UML class diagram. For one, they do not belong to a class, making them completely irrelevant. Two, constants do not belong in a class diagram anyway for reasons I outlined above.I would create a separate UML package diagram for namespace helper (as an aside, I recommend picking a more descriptive name for this namespace) showing that the enum and struct are in the namespace. This diagram type also allows for documenting static members in general and constants specifically.