Devices Profile for Web Services

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The Devices Profile for Web Services (DPWS) defines a minimal set of implementation constraints to enable secure Web Service messaging, discovery, description, and eventing on resource-constrained devices.

Its objectives are similar to those of Universal Plug and Play (UPnP) but, in addition, DPWS is fully aligned with Web Services technology and includes numerous extension points allowing for seamless integration of device-provided services in enterprise-wide application scenarios.

The DPWS specification, initially published in May 2004, defines an architecture in which devices run two types of services: hosting services and hosted services. Hosting services are directly associated to a device, and play an important part in the device discovery process. Hosted services are mostly functional and depend on their hosting device for discovery.

In addition to these hosted services, DPWS specifies a set of built-in services:

Discovery services: used by a device connected to a network to advertise itself and to discover other devices. Support of discovery has led some to dub DPWS as "the USB for Ethernet."
Metadata exchange services: provide dynamic access to a device’s hosted services and to their metadata.
Publish/subscribe eventing services: allowing other devices to subscribe to asynchronous event messages produced by a given service.

DPWS builds on the following core Web Services standards: WSDL 1.1, XML Schema, SOAP 1.2, WS-Addressing, and further comprises WS-MetadataExchange, WS-Transfer, WS-Policy, WS-Security, WS-Discovery and WS-Eventing.

Microsoft's Windows Windows Vista and CE6R2 platforms natively integrates DPWS with a stack called WSDAPI. It is included as part of the Windows Rally technologies.

The latest DPWS specification can be found here: http://schemas.xmlsoap.org/ws/2006/02/devprof/

Because DPWS is a protocol that supports dynamic discovery, and is part of the evolving vision of distributed applications that leverage WS* standards, its application to automation environments is clear. At the 2007 Consumer Electronics Show, a “Next Gen” home was highlighted by an automation system that used DPWS to communicate with a lighting system, audio distribution system, security system, motorized shades, security cameras, thermostats, washers and dryers, and a motorized television mount. The show demonstrated tremendous consumer interest in the prospect of bringing controllable devices into the same environment as digital entertainment, and manufacturers are taking notice.

For many manufacturers, the first step towards DPWS adoption is the creation of a small “device bridge” between their native, usually proprietary, code and Web Services. At least 117 automation and AV products from 37 different vendors currently support DPWS either natively or through a bridge. At the International Security Controls (ISC) trade show, a major security company demonstrated a security system that supported DPWS, while the Kitchen and Bath Show (KBIS) saw two major appliance manufacturers demonstrating Washers and Dryers that communicated using DPWS. A communicative oven has been demonstrated at the International Building Show for the past two years. An even greater sign of the drive towards market acceptance of DPWS is the recent ConnectedLife.Home automation package offered by US retailer Best Buy. The package uses automation software and controllable devices that leverage DPWS for communications.

The EU Research Project SOCRADES composed by heavyweights like ABB, SAP, Schneider Electric, and Siemens, are focusing on implementing, testing and piloting a prototype of DPWS-enabled devices in the automation domain.

Following the SOCRADES Project, a new EU Research Project from ITEA, named SODA (stands for Service Oriented Device and Delivery Architecture) is going further into the development and implementation of an embedded DPWS stack for devices.

An open source implementation of the SODA DPWS stack and its addons (like WS-Management or WS-Security implementations addons) can be freely downloaded from the site SOA4D (SOA 4 Devices).

Within the EU Research Project SIRENA the development of open source DPWS frameworks was launched. The Website "Web Services for Devices" (WS4D.org) provides information, downloads and news about three of this frameworks: One C implementation integrating gSOAP, one Java implementation using Axis, and another Java implementation which can use different Java Editions, including Java ME.