Rating architectural efficiency

Question

How would you rate by numbers the efficiency of a certain design?
What will be your variables?
I can think of:

• Coupling
• Design Patterns use
• Language idioms use.
• Scalability.
• High-viability.
• Code Reuse.
• Flexibility.
• Robustness to errors.
• Testability.
• Design implications on resource use and memory.
• Portability.
• Usage of the correct programming paradigm.
• Design implications on run-time efficiency.
• Encapsulation.

How would you even calculate such a thing?
I've heard of program metrics as the tool of calculating such a thing but I have no idea what it is and how it's done.

I thank anyone who's willing to help.

EDIT: Here is a blog entery about the subject from my newborn blog.

Answer 1

I would like to take into account the following metrics either:

1. Scalability.
   
2. Highviability.

And regarding to your suggestions I don't think memory could be the metric for design efficiency, since it's more implementation based.

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EDIT: (After a comment regarding analytic formula)
I don't think you can find an ultimate formula for computing design efficiency, since it's very subjective. But you can adopt some statistic techniques, define the metrics which really important for you in the design. Afterward define for each metric its weight. Now find different use cases and check how does your design fit them in each metric and give them a grade. After all this you can normalize and compute the value with V= Sum(W_i*G_i)/Sum(W_i), where W_i is weight and G_i is a grade. This way you can specify whatever is important for you in the design and calculate accordingly.

Answer 2

There are a couple of tools out there that can do this for you. One I've used is Checkstyle - Metrics.

I can't say really consider these metrics when designing, but use them on slow/lazy afternoons when I'm looking for a bit of code to attack.

Answer 3

Code reuse. While you perhaps can't count it as a positive value you can count it's underuse as a negative value and get a cumulative penalty score for bad code reuse.

Answer 4

This might be of interest as well:

ATAM (Wikipedia) and ATAM: Method for Architecture Evaluation