Comments on: Depend in the direction of stability http://blog.robbowley.net/2009/05/14/depend-in-the-direction-of-stability/ adventures in extreme programming Thu, 15 Jul 2010 11:34:19 -0700 http://wordpress.org/?v=2.8.4 hourly 1 By: rob http://blog.robbowley.net/2009/05/14/depend-in-the-direction-of-stability/comment-page-1/#comment-1956 rob Fri, 15 May 2009 11:09:13 +0000 http://blog.robbowley.net/?p=474#comment-1956 Among other places I referred to the c2wiki which suggests this is not always the case: http://c2.com/cgi/wiki?StableDependenciesPrinciple Not a reliable source I suppose... Among other places I referred to the c2wiki which suggests this is not always the case:
http://c2.com/cgi/wiki?StableDependenciesPrinciple

Not a reliable source I suppose…

]]> By: Jason Gorman http://blog.robbowley.net/2009/05/14/depend-in-the-direction-of-stability/comment-page-1/#comment-1951 Jason Gorman Fri, 15 May 2009 09:19:52 +0000 http://blog.robbowley.net/?p=474#comment-1951 SDP has a very well-defined meaning in so much as "stability" and "instability" have well-defined meanings in the context of package dependencies. Instability = efferent couplings / (efferent + afferent couplings) Stability = 1 - instability Any other interpretation wouldn't be the SDP :-) SDP has a very well-defined meaning in so much as “stability” and “instability” have well-defined meanings in the context of package dependencies.

Instability = efferent couplings / (efferent + afferent couplings)

Stability = 1 – instability

Any other interpretation wouldn’t be the SDP :-)

]]> By: rob http://blog.robbowley.net/2009/05/14/depend-in-the-direction-of-stability/comment-page-1/#comment-1948 rob Fri, 15 May 2009 07:54:01 +0000 http://blog.robbowley.net/?p=474#comment-1948 That's one way to measure the stability of a package and a very good one because it can be measured through metrics such as Afferent and Eferrent coupling. However, in my humble understanding there are other ways. You could also identify unstable packages by checking the change logs in your source control repository or by speaking to colleagues. I have interpreted it thus to illustrate a particular issue we are facing where we have a some "mother" (e.g "Common", "Domain") packages which all our products are using and have become a dumping ground for all and sundry. What is worse is that none of these mother packages are being versioned and used as compiled assemblies, but are being included as projects within the solutions so are being considered part of the source code for each product. I hope, in your eyes, this is a satisfactory interpretation of the SDP. That’s one way to measure the stability of a package and a very good one because it can be measured through metrics such as Afferent and Eferrent coupling. However, in my humble understanding there are other ways. You could also identify unstable packages by checking the change logs in your source control repository or by speaking to colleagues.

I have interpreted it thus to illustrate a particular issue we are facing where we have a some “mother” (e.g “Common”, “Domain”) packages which all our products are using and have become a dumping ground for all and sundry. What is worse is that none of these mother packages are being versioned and used as compiled assemblies, but are being included as projects within the solutions so are being considered part of the source code for each product.

I hope, in your eyes, this is a satisfactory interpretation of the SDP.

]]> By: Jason Gorman http://blog.robbowley.net/2009/05/14/depend-in-the-direction-of-stability/comment-page-1/#comment-1927 Jason Gorman Thu, 14 May 2009 21:58:21 +0000 http://blog.robbowley.net/?p=474#comment-1927 In this context, a package is said to be more stable if it has less dependencies on other packages. If a package depends on lots of other packages, then a change to any none of these packages may force us to recompile, retest and redeploy that package. Packages that depend more on other packages are said to be more "instable". So we should favour depending on packages that have fewer dependencies on other packages (are less instable). In this context, a package is said to be more stable if it has less dependencies on other packages.

If a package depends on lots of other packages, then a change to any none of these packages may force us to recompile, retest and redeploy that package. Packages that depend more on other packages are said to be more “instable”.

So we should favour depending on packages that have fewer dependencies on other packages (are less instable).

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