What is the meaning of "The Composition Over Inheritance Principle"?

Question

I have a few questions about the following phrase:

The Composition Over Inheritance Principle.

1. Is over a preposition?

2. Is this a complete sentence?

3. I think it means one of the following. Which is correct?

   • The composition that is better than Inheritance?
   • The composition is better than Inheritance?

4. Can the form '{noun}+{preposition}+{noun}' create a complete sentence?

Answer 1

Let me answer these slightly out of the order you asked them in. To begin, is this quotation a complete sentence?

The Composition Over Inheritance Principle.

Question 2: ❌ No, it is not. You can tell because it does not contain a verb. Your dictionary will tell you that "over" can be either a preposition, an adverb, an adjective, or a prefix. None of these options are a verb. None of the other words are verbs either. Without a verb, this is not a sentence.

What is it? It's a noun phrase. A noun phrase is an entire phrase that acts as a single noun. It could be the subject of a sentence, or the object, but it is not the entire sentence by itself.

Which is related another of your questions, can the form '{noun}+{preposition}+{noun}' create a complete sentence? And the answer is, again:

Question 4: ❌ No, it cannot. Again, a complete sentence requires a verb.

Now we can get to the details. What does it mean? "The composition that is better than Inheritance?" or "The composition is better than Inheritance?"

Question 3: ❌ Neither option is correct. As you were attempting to rephrase the quoted text, you are applying "The" to "composition". This is not correct. "The" actually applies to "Principle".

The Principle

Which Principle is it?

The Principle of Composition over Inheritance

And that finally leads us to your first question. Is over a preposition?

Question 1: ✅ Yes! Again, "over" can be either a preposition, an adverb, an adjective, or a prefix. It's not a prefix, because it isn't part of another word. It isn't an adverb, because there is no verb to modify. It isn't an adjective, because that would mean we have "noun + adjective + noun" which doesn't make sense. So it must be a preposition.

As a preposition, what does "over" mean here? It means "is better than" or "is more important than" or "should be used instead of".

So now we have:

The Principle that Composition is better than Inheritance.
The Principle that Composition is more important than Inheritance.
The Principle that Composition should be used instead of Inheritance.

Note that even these rephrasings are not complete sentences, as they do not contain a true verb. It looks like there's a verb in each (is/used), but these verbs are merely part of the description of Principle. The "that" makes the next several words part of the noun phrase.

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Now. Two of your questions are focused on it being a complete sentence or not. You didn't provide the source where you found this noun phrase, but I'm assuming that the source used it as if it were a complete sentence-- that is, with a period at the end. In casual speech and casual writing, noun phrases can sometimes be used as if they were a complete sentence. For example:

What day is it today?
Wednesday.

Here, "Wednesday" is not a complete sentence. It's just a noun! The trick is, in casual speech, parts of the sentence can be implied, and don't need to be said.

What day is it today?
[It is/It's] Wednesday.

Just as "Wednesday" is a simple noun, and not a sentence, "The Composition over Inheritance Principle" is a noun phrase, and not a sentence... and yet it could be placed in a sentence by itself if the context would allow it.

I hope this helps!