利用CWC映射,本文获得了对称度量空间和g可度量空间的特征,建立了几个度量化定理,改进了一些已知结果.主要的定理是证明正则空间X是可度量化空间当且仅当存在X上的CWC映射g满足如下条件: (Ⅰ)若序列{xn}和{yn)对于每一n∈N有xn∈g(n,yn)且xn→x,则yn→x. (Ⅱ)若序列{xn}和{yn}对于每一n∈N有yn∈g(n,yn)且xn→x,则yn→x.
By using the concept of CWC, we establish several new metrization theorems, and obtain the characterization of g-metrizable spaces and symmetric spaces, which generalize some known results.