RE: analysis of YANG vs. RELAX NG

["Romascanu, Dan (Dan)" <[e-mail]>]

Lisa,

As Juergen has pointed, we differentiate in the OPS area between
information model and data model. I believe that much of what you say
about ontology and data model in English actually relates to what we
call information models. There was an effort to start a new information
model (nim) in the IETF, we had a BOF some time ago, but the general
feeling was that the endeavor is too big, the field too dynamic, and
other SDOs may be better places for IM definition. The approach that you
see today which starts with the definition of a data modeling language
and uses it to perform a one step modeling resulting in an interoperable
data structure is the result of accumulating experience and a few basic
requirements derived from the needs of the operators performing network
management operations - scalability, extensibility, machine readable and
yet human comprehensible format, interoperability between different
vendors agents and managers, form factor that allows rather complex and
large configuration data bases to run or relatively resource challenged
devices. 

Dan


 
 

> -----Original Message-----
> From: Lisa Dusseault [mailto:[e-mail]] 
> Sent: Tuesday, November 27, 2007 9:54 PM
> To: [e-mail]
> Cc: [e-mail]; Leif Johansson
> Subject: Re: analysis of YANG vs. RELAX NG
> 
> Another question to answer, is why is having a data model (an
> ontology) not enough?  The question of needing a standard 
> data model must be separated from the need for a custom 
> modeling language.  Some of the justifications I've seen so 
> far for a modeling language have really been justifying only 
> a standard data model.
> 
> Of course using XML as the data format doesn't, by itself, 
> give enough of a common data model for 3rd-party NetConf 
> tools to understand arbitrary data.  NetConf probably does 
> need a common data model, perhaps defining how IDs are 
> expressed and what a container is, what is a netconf "object" 
> that can be operated on.
> 
> But a common data model does not need to depend on a modeling 
> language at all.  Put it differently: a sufficiently strong 
> common data model can work with multiple modeling languages 
> without harming interoperability.  Thus, having a standard 
> data model that is independent of the modeling language can 
> be a real win for clarity and robustness and somewhat more 
> proof against changing stylistic preferences.
> 
> The commonest approach for IETF protocols that deal with an 
> ontology is to define the data model in English, limiting the 
> ways the data can be expressed to something that becomes 
> essentially self- describing (the name of a new thing/object, 
> and its contents or value, can be derived from the document 
> without seeing a specific schema).  LDAP is one of the 
> clearest examples of this.  An LDAP agent can handle custom 
> content because it follows the expected data model. There's 
> no need, in LDAP, for a special language to describe new 
> attributes.  The iCalendar and vCard formats are the same.  
> SNMP is really different in having a special language to 
> learn, and using that in specs.
> 
> My experience with description languages or other 
> formalizations is that these often take the place of proper 
> specification.  Authors think that they are done when they've 
> written the code that describes the format.  However, the 
> most important aspect to a new standard schema is usually 
> what it *means*.
> 
> Lisa
> 
> On Nov 27, 2007, at 8:37 AM, Juergen Schoenwaelder wrote:
> 
> > On Tue, Nov 27, 2007 at 01:45:30PM +0100, Leif Johansson wrote:
> >
> >> I don't know about RelaxNG, but it is pretty close to OWL. 
> Apart from 
> >> the C-like syntax (which might be important to some) the example 
> >> suggests a modeling language which supports classes, packages, 
> >> properties (possibly associations?) and a form of multiple 
> >> inheritance.
> >>
> >> While I am as happy as the next guy that we won't be 
> seeing RFCs with 
> >> XMI in them anytime soon I am curious as to why something like OWL 
> >> isn't a strong candidate for something like this. Is it just 
> >> "anti-XML"
> >> or is there something more substantial to it?
> >
> > NETCONF uses XML for data encoding and is this is just fine.
> >
> > YANG is a domain specific data modeling language designed 
> to support 
> > NETCONF (no more, no less). The YANG language reflects many 
> years of 
> > experience with other network management data modeling languages in 
> > the IETF and proprietary languages created by NETCONF 
> implementors to 
> > support their implementations (after figuring out that creating 
> > adapted subset languages did not work well in their 
> companies or for 
> > their customers).
> >
> > While YANG clearly lacks features such as multiple inheritance or 
> > support for semantic web reasoning engines, we feel that it helps a 
> > lot in writing understandable and extensible NETCONF data 
> models and 
> > in addition it can enjoy long-term predictability and stability.
> >
> > /js
> >
> > -- 
> > Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> > Phone: [phone]         Campus Ring 1, 28759 Bremen, Germany
> > Fax:   [phone]         <http://www.jacobs-university.de/>
> >
> >
> 
>