Re: [CDNi] CDNI Metadata Interface

[HeXiaoyan <[e-mail]>]

Hi Kevin,
I share the view that the concept of Domain is useful, my suggestion is
linking metadata to Hostname and keep the Domain,
i.e. something like the figure below. Benefit is metadata associated with
one custormer can be grouped even different
Hostnames belong the Domain has different metadata value.


  +----------+
 |        | 1
 | Agent   +---------------------------+
 |        |                |
 +----+-----+                  |
      | 1..*                |
      |                    |
      | 1                   | 1
  +----+-----+             +----+-----+
 |         |          |          |
 | Domain  |          |  Metadata |
 |         |          |          |
  +----+-----+             +-----+----+
      | 1                   |
      |                     |
      | 1..*                 |
  +----+-----+                 |
 |         |    1   0..*     |
 | Hostname +----------------------------+
 |         |
  +----------+

Thanks.

Best Regards
Xiaoyan(Susan) He
-----Original Message-----
From: Kevin J Ma [mailto:[e-mail]] 
Sent: Friday, October 14, 2011 10:26 PM
To: HeXiaoyan; [e-mail]
Subject: RE: [CDNi] CDNI Metadata Interface

Hi Susan,

  responses inline:

> -----Original Message-----
> From: HeXiaoyan [mailto:[e-mail]]
> Sent: Friday, October 14, 2011 5:35 AM
> To: Kevin J Ma; [e-mail]
> Subject: RE: [CDNi] CDNI Metadata Interface
> 
> Hi Kevin,
> Thanks for the response. Some further concern,
> - I don't quite understand the restriction that require metadata of all
> hostnames in one Domain have same value. The case exist that for a
> specific
> metadata different hostnames often have different value. Compare with
> creating multiple Domains with less hostname sharing the same metadata, I
> think link metadata to hostname not Domain is more simpler.

>From a conceptual perspective, it could be argued that the domain
object is extraneous.  As an implementation detail, however, the
multi-table joins, imo, were simplified by having a central object
to define the domain, so I added one.  From an operator perspective,
having a way to group multiple hostnames also seems useful, even
though, in the degenerate case, you could just have one hostname per
domain.  If there is a concensus view that the domain is unnecessary,
it could be removed.

> -I interpret the role of the Agent object is to identify entities
> communicated (correct me if I'm wrong), other interfaces in CDNI e.g.
> Logging interface needs such an parameter as well, a universal solution
> for
> that would be good, do you think the Agent object introduced in your draft
> could also be applicable for other interfaces?

I agree that the other interfaces (control/logging) will require some
type of authentication and security.  The agent concept could certainly
be extended to other interfaces, and I agree that it would be good to
have the same solution for all interfaces

thanx.

--  Kevin J. Ma

> Best Regards
> Xiaoyan(Susan) He
> 
> -----Original Message-----
> From: Kevin J Ma [mailto:[e-mail]]
> Sent: Tuesday, October 11, 2011 11:30 PM
> To: HeXiaoyan; [e-mail]
> Subject: RE: [CDNi] CDNI Metadata Interface
> 
> Hi Susan,
> 
>   thanx for the comments, responses inline:
> 
> > -----Original Message-----
> > From: HeXiaoyan [mailto:[e-mail]]
> > Sent: Tuesday, October 11, 2011 5:28 AM
> > To: Kevin J Ma; [e-mail]
> > Subject: RE: [CDNi] CDNI Metadata Interface
> >
> > Hi Kevin,
> > Some quick questions and comments on this draft,
> > >The Metadata objects are each associated with a URI within the Domain
> and
> > accessible through any of the Hostnames...
> > - Could you further explain or give an example how a metadata is
> accessed
> > by
> > a Hostname within the Domain? And a further question is how the data
> model
> > works if a metadata is only associated with a specific Hostname within
> one
> > Doman?
> 
> I was assuming that metadata would be valid for all hostnames.  If a
> hostname
> needed separate metadata, a new domain would be required.  I was thinking
> of
> hostname as a first level restriction.  My implementation does something
> along
> the lines of the following (where hostname is checked before metadata
> lookup):
> 
>   domain = get_param_from_query_string(getenv("QUERY_STRING"), "domain")
>   if (!db_verify_hostname_for_domain(getenv("SERVER_NAME"), domain))
>     return error
>   metadata = db_get_metadata_by_uri_domain_agent(getenv("REQUEST_URI"),
>                                                  domain,
> getenv("REMOTE_USER"))
>   xml = generate_xml_for_metadata(metadata)
>   return xml
> 
> > - The relationship between Agent objects and Metadata objects is a
> > one-to-one relationship, does this mean one agent can only access one
> > Metadata within one Domain?
> 
> That is a typo in the doc, good catch, thanx!  It should be one to many.
> Each metadata must be associated with a single agent, but an agent can be
> associated with multiple metadata.  Agent-1 could have metadatas A, B, and
> C, while agent-2 could have a separate value for metadatas A and B, and
> also
> have its own metadata D (that agent-1 does not have access to)
> 
> > > The association of each Metadata to an Agent allows different Agents
> to
> > retrieve different Metadata values for a given URI in the given Domain.
> > - Don't understand why each Metadata object needs to be bind with an
> Agent
> > explicitly, IMO, whether to return different value to different Agents
> is
> > an
> > inside process of the upCDN, what downCDN needs to do is just transmit
> its
> > identifier to the upCDN when retrieve a Metadata.
> 
> I think the fact that a uCDN would want/need to give out different values
> to
> different dCDNs requires that there be a way to represent and store that
> information.  Having it explicitly in the model, i think, simplifies the
> implementation and guarantees that all implementation give this issue
> proper
> consideration.
> 
> > - Which entity is responsible for creating the Agent objects within one
> > Domain? Does the CP can 'see' the downCDNs and creates corresponding
> Agent
> > objects and other CDNs on the way just transmitted it or each upCDN
> > located
> > in the cascaded path creates a Agent object for each its downCDN?
> 
> This is a good question.  Different agents would need to be create by
> different
> entities, as you mention.  I would expect each CDN to create agents to
> represent
> those (outside that CDN) who need access to the metadata interface.
> 
> thanx!
> 
> --  Kevin J. Ma
> 
> > Thanks.
> > Best Regards
> > Xiaoyan(Susan) He
> >
> > -----Original Message-----
> > From: [e-mail] [mailto:[e-mail]] On Behalf Of
> > Kevin J Ma
> > Sent: Friday, October 07, 2011 1:21 PM
> > To: [e-mail]
> > Subject: [CDNi] CDNI Metadata Interface
> >
> > Hi all,
> >
> >   Just uploaded a new I-D with a proposed metadata model and API:
> >
> >     http://www.ietf.org/internet-drafts/draft-ma-cdni-metadata-00.txt
> >
> >   The model takes a rather generic approach to metadata representation
> >   to support opaque metadata and addresses some of the security issues
> >   associated with metadata retrieval.  Comments welcome.
> >
> > thanx.
> >
> > --  Kevin J. Ma
> >
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