Device Description Language (DDL)

  1. Introduction
  2. Resources

Introduction

Device Description Language (DDL) is an XML language for describing devices controllable across the network. It differs from most other such languages in that rather than categorising equipment by “type of device” it does so by “type of control”. This page contains various resources relating to DDL.

DDL is a part of Architecture for Control Networks (ACN) an ANSI Standard (E1.17 2006) developed by the Entertainment Services and Technology Association (ESTA).

What does DDL do?

The ACN model for control completely separates the protocol for accessing devices from any knowledge of the functionality of those devices. The protocol merely provides a method for accessing abstract "properties" of any device. In order to make sense of this, a controller has to know what those properties represent and this information is provided externally in the form of a Device Description which relates the abstract properties to the control concepts which govern the particular device.

DDL outside of ACN

The fact that the device description is almost completely separate from the control protocol, means that the same description language can be used with other control protocols. The DDL specification allows it to be adapted to different protocols by customising just one or two elements.

Examples of protocols for which DDL could be used with minor customisation range from SNMP (where DDL could provide a machine readable descritpion of the functionality of an arbitrary MIB) through to the DMX512 data link format used extensively in entertainment lighting.


DDL Resources

The DDL Specification is part of the ACN documentation. I will gather additional and ancilliary resources on this page as they are devloped.

DDL Draft Specification

The final public draft of DDL is available here for interest only. The definitive specification for DDL is part of ANSI Standard E1.17 2006 which is available from ESTA or ANSI. This draft was the text which was put to the last public review prior to ANSI approval. It has been reformatted for web display. A pdf version is available on the ACN page.

Final Public Review Draft

DDL Behaviors

DDL uses “behaviors” to characterise device properties. While just about readable in raw XML, behaviors are better transformed for presentation Engineering Arts have developed tools for summarising the behaviors in any DDL file – some results are shown here.

DMP Core behaviors HTML formatted

DMP Core behaviors Original XML

DDL Schemas

Three schemas are part of the DDL specification: Two XML DTDs, one for basic DDL and one specific to the DMP protocol; and a schema for DDL with DMP in the compact syntax of RELAX NG.

DDL basic DTD

DDL for DMP DTD

DDL for DMP RELAX NG schema


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