Digital Ecosystem is a new word for dynamic IT business environments. Digital Ecosystem can consist of various enterprise federations such as competing, collaborating and stable or unstable ones. They make it difficult to implement identity management for the environment. Existing solutions are either too restricting and inflexible to support the dynamic nature of ecosystems since they are too complex and difficult to adopt. This paper is to propose an distributed identity management model for automated processing of identity information between ecosystems. It is featured with being practical, clear and easy to deploy. And it is based on the new OASIS SAML3.0 standard to provide interoperability between existing identity technologies. This paper presents the basic and extended identity model for single service and multiple services. The model presented in this paper can be applied to enterprise context easily.