This document describes the Data Access Layer Interface (DALI). DALI defines the base web service interface common to all Data Access Layer (DAL) services. This standard defines the behaviour of common resources, the meaning and use of common parameters, success and error responses, and DAL service registration. The goal of this specification is to define the common elements that are shared across DAL services in order to foster consistency across concrete DAL service specifications and to enable standard re-usable client and service implementations and libraries to be written and widely adopted.