Blockchain as a service (BaaS) is a cloud service category in which the capabilities provided to the cloud service customer are the ability of setting up blockchain platform, and development decentralized application using blockchain technologies. In BaaS, an integrated developing environment (IDE) for CSCs is provided to create, deploy and operate decentralized applications. This Recommendation introduces blockchain and blockchain as a service. This Recommendation also provides functional requirements of blockchain as a service which is derived from use cases.