Simple Path & Prime Path & Prime Path Coverage

1，如果要理解prime path，首先要引入简单路径

simple path:

A path from node ni to nj is simple if no node appears more than once, except possibly the first and last nodes are the same.

从定义可知：①简单路径中没有内部环；②环路是简单路径。

 

2，此时，我们再看主路径的定义

Prime Path : A simple path that does not appear as a proper subpath of any other simple path。

即，主路径（基路径）要满足两个条件：

①是一条简单路径；

②它不能是其他简单路径的子路径；（即不能被比它长的简单路径所包含）

 

直接上例子：

 

3，接着我们引出主路径覆盖的定义

Prime Path Coverage(PPC)：TR contains each prime path in G.

A simple, elegant and finite criterion that requires loops to be executed as well as skipped.

可以看出，PPC会覆盖长度为0，1及以上的路径；所以，PPC包含点覆盖，边覆盖！

PPC almost, but not quite, subsumes EPC…

但是，PPC不包含EPC（边対覆盖）；(由简单路径的特点——非端节点不能出现两次及以上  决定）

e.g:

If a node n has an edge to itself, EPC will require [n, n, m]

[n, n, m] is not prime.