  A traditional database systems is organized around a single data model that
determines how data can be organized, stored and manipulated. But the vision of
this paper is to develop new principles and techniques to manage multiple data
models against a single, integrated backend. For example, semi-structured,
graph and relational models are examples of data models that may be supported
by a new system. Having a single data platform for managing both
well-structured data and NoSQL data is beneficial to users; this approach
significantly reduces integration, migration, development, maintenance and
operational issues. The problem is challenging: the existing database
principles mainly work for a single model and the research on multi-model data
management is still at an early stage. In this paper, we envision a UDBMS
(Unified Database Management System) for multi-model data management in one
platform. UDBMS will provide several new features such as unified data model
and flexible schema, unified query processing, unified index structure and
cross-model transaction guarantees. We discuss our vision as well as present
multiple research challenges that we need to address.
