Re: [ws-dd] RE: Issue 134 - DPWS - No reliable way to retrievediscovery metadata of devices

[Elmar Zeeb <elmar.zeeb@uni-rostock.de>]

Dan Driscoll schrieb:
>
> The model I fall back on is that discovery information is available 
> from a Device using Directed Discovery, and that the metadata should 
> not duplicate this information unless necessary.
>
>  
>
> I think we can solve this problem by making Types and Scopes mandatory 
> in Directed ProbeMatches messages.  This would be similar to the rules 
> around managed Hello sent to a discovery proxy.
>
>  
>
> What are your thoughts on this solution?
>
Yes, this is a good solution. I checked that receiving and responding to 
directed Probe messages is mandatory. This solution can be used in 
client implementations to retrieve all types and scopes of a device in a 
reliable way.

If we add this requirement to the spec we can also add a note about the 
interoperability for client implementations concerning discovery in 
dpws. Types and Scopes may be omitted in multicast discovery response 
messages but not in directed discovery response messages.
>
>  
>
> Thanks Elmar
>
> --D
>
>  
>
> *From:* Ram Jeyaraman [mailto:Ram.Jeyaraman@microsoft.com]
> *Sent:* Tuesday, December 16, 2008 8:33 AM
> *To:* ws-dd@lists.oasis-open.org
> *Subject:* [ws-dd] Issue 134 - DPWS - No reliable way to retrieve 
> discovery metadata of devices
>
>  
>
> This issue is assigned the number 134. For further discussions on this 
> issue, please refer to this issue number or use this thread.
>
>  
>
> *From:* Elmar Zeeb [mailto:elmar.zeeb@uni-rostock.de]
> *Sent:* Monday, December 15, 2008 3:40 PM
> *To:* Ram Jeyaraman
> *Subject:* New Issue for DPWS
>
>  
>
> Description: No reliable way to retrieve discovery metadata of devices
> Document: wsdd-dpws-1.1-spec-wd-02
> Line number:
>
> All type fields in WS-Discovery and DPWS are optional. There should be 
> ONE way to retrieve the types, supported by a device, without probing 
> for every type. As the types should be optional in the discovery 
> metadata, to solve problems related to message size, the types should 
> be listed in the relationship metadata section. The increased message 
> size of WS-Transfer messages is not as problematic as an increased 
> message size within WS-Discovery (UDP fragmentation). At the moment 
> there is no reliable way to retrieve all device types of a device. 
> This problem exists especially for generic clients.
>
> The same problem exists for scopes. This problem is less problematic 
> as scopes don't express the device functionality.
>
> Proposed solution: Make Host field in relationship metadata mandatory 
> and also make types field in the Host field mandatory.
>
> There is no proposed solution for the scopes problem.
>
> -- 
> *******************************************************************************
>   Dipl.-Inf. Elmar Zeeb
>   Universit�t Rostock, Fakult�t f. Informatik und Elektrotechnik
>   Institut f. Angewandte Mikroelektronik und Datentechnik
>   University of Rostock, Faculty of CS and EE
>   Institute of Applied Microelectronics and Computer Engineering,
>   18051 Rostock
>   Deutschland/Germany
>   Tel. : ++49 (0)381 498 - 7262
>   Fax  : ++49 (0)381 498 - 7252
>   Email: elmar.zeeb@uni-rostock.de <mailto:elmar.zeeb@uni-rostock.de>
>   www  : http://www.imd.uni-rostock.de/, http://www.ws4d.org/
> *******************************************************************************


-- 
*******************************************************************************
  Dipl.-Inf. Elmar Zeeb
  Universit�t Rostock, Fakult�t f. Informatik und Elektrotechnik
  Institut f. Angewandte Mikroelektronik und Datentechnik
  University of Rostock, Faculty of CS and EE
  Institute of Applied Microelectronics and Computer Engineering,
  18051 Rostock
  Deutschland/Germany
  Tel. : ++49 (0)381 498 - 7262
  Fax  : ++49 (0)381 498 - 7252
  Email: elmar.zeeb@uni-rostock.de
  www  : http://www.imd.uni-rostock.de/, http://www.ws4d.org/
*******************************************************************************