  With the spread of services related to cloud environment, it is tiresome and
time consuming for users to look for the appropriate service that meet with
their needs. Therefore, finding a valid and reliable service is essential.
However, in case a single cloud service cannot fulfil every user requirements,
a composition of cloud services is needed. In addition, the need to treat
uncertainty in cloud service discovery and composition induces a lot of
concerns in order to minimize the risk. Risk includes some sort of either loss
or damage which is possible to be received by a target (i.e., the environment,
cloud providers or customers). In this paper, we will focus on the uncertainty
application for cloud service discovery and composition. A set of existing
approaches in literature are reviewed and categorized according to the risk
modeling.
