Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm reading this paper:, and the authors used the symbol $R_{0}^{+}$ in the definition of Exact Exception Problem, such as $D: P(I) \rightarrow R_{0}^{+}$. Could anyone please help me understand what the symbol $R_{0}^{+}$ means? It seems refer to the set of real numbers, but if that's the case, what are the subscript and superscript for?


share|cite|improve this question
I am not fully sure but I carefully understand the paper it seems to me that $R_{0}^{+}$ denotes set of all positive real number except $0$ means $(0,\infty)$.(I conclude it from cardinality functio) – iostream007 Jul 20 '13 at 20:53
up vote 2 down vote accepted

It is the half line $[0,+\infty)$.

share|cite|improve this answer

$\mathbb R^+$ alone denotes the positive real numbers, and the subscript we see here $0$ denotes the inclusion of zero, as well. So all together, we have the set $$\mathbb R_0^+ = \{x\mid x\in \mathbb R, x\geq 0\}$$

This set is sometimes denoted by $\mathbb R_{\geq 0}$. There is no one universally used notation to describe the set of non-negative real numbers. So it's usually best that authors define the notation they plan to use.

share|cite|improve this answer
Are we sure AAAI does not have a "standard" for such notation? – GEdgar Jul 20 '13 at 20:51

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.