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Important relationships

There are several relationships that are important for modeling:

In UML 1 (and sometimes elsewhere at OMG) the word, 'instance,' and the phrase, 'instance of,' are used with at least five or six different meanings. 

So we find in the UML specification and in writing about UML and MOF, that 'instance' is used with all these meanings, for example:

It is possible that these are not all distinct meanings; perhaps in some pair of the usages above the meanings of 'instance of' are identical.  It is certain that there is more than one distinct meaning of 'instance of' in the examples above. Likely somewhere between six and eight distinct meanings.

 

Life will be, not only simpler, but more pleasant, if we give each distinct relationship a different name.  For example:

A metaphor:

That cat is represented by 'cat'.  Whiskers is represented by 'Whiskers.' 
Whiskers is an instance of  Domestic Shorthair.
'Whiskers' is an example of a proper noun; 'cat' is an example of a common noun.
'Whiskers is my cat' uses English.

 

Another metaphor:

Whiskers is represented by cat.gif (1234 bytes).        
   cat.gif (1234 bytes) is an example of an icon.

Three concrete examples:

The OMG web server is represented by the object, omgWebServer.
The object, omgWebServer is an instance of the type, WebServer.
The object, omgWebServer is an instantiation of the specification, Specification for an OMG web server.
The object, omgWebServer is an instantiation of the Java class, JWebServer.
The phrase, 'OMG web server,' is an example of a noun phrase.
The object, omgWebServer, is an example of a UML Object

Whiskers is represented by the object, Whiskers.
Whiskers is an instance of the type, Pet.
Whiskers is an instantiation of  the class, Cat.
Whiskers is an example of a UML object.

<work in progress:>

In these memory locations The instructions in these memory locations is code and this data here is the line of code is excuting the program

 

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