Assemblies that don't satisfy the Abstractness/Instability principle

Rule ND1407 Architecture

The Abstractness versus Instability Diagram identifies assemblies potentially painful to maintain (concrete and stable) and potentially useless (abstract and instable).

- Abstractness: many abstract types (interfaces, abstract classes), few concrete ones.

- Stability: types used by many types from other assemblies (painful to modify).

The normalized distance ([0.0 … 1.0]) from the idealized line A + I = 1 (main sequence) indicates the abstractness/stability balance; this rule warns above 0.7. Metric explained here: https://www.ndepend.com/docs/code-metrics#DitFromMainSeq Concepts introduced by Robert C. Martin in 1994: http://www.objectmentor.com/resources/articles/oodmetrc.pdf

How to fix

The assembly is either potentially painful to maintain (massively used, mostly concrete: create abstractions to reduce coupling with concrete implementations) or potentially useless (mostly abstract, not used enough: review the design).

Severity is Low: this principle informs about code structure but is not actionable. Fixing actionable Architecture and Code Smells issues will push the scores in the right direction.

CQLinq source

This rule is written in CQLinq, C# LINQ over the NDepend code model. It ships with every new NDepend project: you can read it, adapt it, or use it as a starting point for your own custom rules.

// <Name>Assemblies that don't satisfy the Abstractness/Instability principle</Name>
// <Id>ND1407:AssembliesThatDontSatisfyTheAbstractnessInstabilityPrinciple</Id>

warnif count > 0 from a in Application.Assemblies 
  where a.NormDistFromMainSeq > 0.7
  orderby a.NormDistFromMainSeq descending
select new { 
   a,
   a.NormDistFromMainSeq,
   Debt = 10.ToMinutes().ToDebt(),
   Severity = Severity.Low
}

//<Expl>
// The *{0}* has a *Normalized Distance from the Main Sequence* metric equals to {1}.
// To understand this metric, its implications, and the necessary corrective actions, 
// please read this rule description.
//</Expl>

//<Desc>
// The **Abstractness versus Instability Diagram** identifies assemblies
// **potentially painful to maintain** (concrete and stable) and
// **potentially useless** (abstract and instable).
//
// - **Abstractness**: many abstract types (interfaces, abstract classes),
// few concrete ones.
//
// - **Stability**: types used by many types from other assemblies (*painful
// to modify*).
//
// The *normalized distance* ([0.0 … 1.0]) from the idealized line
// **A + I = 1** (*main sequence*) indicates the abstractness/stability
// balance; this rule warns above 0.7. Metric explained here:
// https://www.ndepend.com/docs/code-metrics#DitFromMainSeq
// Concepts introduced by *Robert C. Martin* in 1994:
// http://www.objectmentor.com/resources/articles/oodmetrc.pdf
//</Desc>

//<HowToFix>
// The assembly is either *potentially painful to maintain* (massively used,
// mostly concrete: create abstractions to reduce coupling with concrete
// implementations) or *potentially useless* (mostly abstract, not used
// enough: review the design).
//
// Severity is **Low**: this principle informs about code structure but
// **is not actionable**. Fixing actionable **Architecture** and
// **Code Smells** issues will push the scores in the right direction.
//</HowToFix>

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