The Model-Driven Service Adaptation Layer (MD-SAL) is message-bus inspired extensible middleware component that provides messaging and data storage functionality based on data and interface models defined by application developers (i.e. user-defined models).

The MD-SAL:

• Defines a common-layer, concepts, data model building blocks and messaging patterns and provides infrastructure / framework for applications and inter-application communication.

// FIXME: Common integration point / reword this better

• Provide common support for user-defined transport and payload formats, including payload serialization and adaptation (e.g. binary, XML or JSON).

The MD-SAL uses YANG as the modeling language for both interface and data definitions, and provides a messaging and data-centric runtime for such services based on YANG modeling.

The MD-SAL provides two different API types (flavours): +

Binding:: MD-SAL APIs which extensively uses APIs and classes generated from YANG models, which provides compile-time safety and allows developers to use more natural way to work with data. DOM:: (Document Object Model) APIs which uses DOM-like representation of data, which makes them more powerful, but provides less compile-time safety.

NOTE: Model-driven nature of the MD-SAL and DOM-based APIs allows for behind-the-scene API and payload type mediation and transformation to facilitate seamless communication between applications - this enables for other components and applications to provide connectors / expose different set of APIs and derive most of its functionality purely from models, which all existing code can benefit from without modification. For example RESTCONF Connector is an application built on top of MD-SAL and exposes YANG-modeled application APIs transparently via HTTP and adds support for XML and JSON payload type.

MD-SAL is part of OpenDaylight Project, where we use Gerrit for incoming patch reviews.