Re: [CDNi] CDNI Metadata Interface

[HeXiaoyan <[e-mail]>]

Kevin,
> Adding the one-to-many relationship
> between the hostname and metadata tables would cause duplicate entries
> in the metadata table (one per hostname)?
Sorry, after reading the draft again, I have to say my intention was that
the relationship between the Hostname and Metadata object should be a
one-to-zero or one-to-one relation like the figure below. All metadata
associated with one hostname or one url prefix which at least containing a
hostname should be grouped in one Metadata object (i.e. explicitly define
all the properties of each hostname in one Metadata object). I think this is
more straight-forward and consistent with the existing today CDN metadata
model.  Is it possible for you to consider modifying your proposal on this?

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

When reading through the examples in section 3.3.3, I found no agent id/name
is conveyed in the metadata retrieval message, I remember we discussed that
for different agent the upCDN may response with different value of a
metadata, would you double check that?
Thanks.

Best Regards
Xiaoyan(Susan) He

-----Original Message-----
From: Kevin J Ma [mailto:[e-mail]] 
Sent: Tuesday, October 18, 2011 2:26 AM
To: HeXiaoyan; [e-mail]
Subject: RE: [CDNi] CDNI Metadata Interface

Hi Susan,

  ok, I think I understand now.  In writing the draft, I was not sure if 
  this would be a typical use case.  Adding the one-to-many relationship
  between the hostname and metadata tables would cause duplicate entries
  in the metadata table (one per hostname)?  One alternative would be to
  use a many-to-many relationship instead, though verification of domain
  constraints on creation becomes more complex.  In general, if we think
  that this flexibility is required, I have no issue with making changes
  to the model, however, if it is unlikely to be used, I would favor the
  simpler approach.

  Is a one-to-many relationship between the hostname and metadata tables
  that much better than removing the hostname table completely (and just
  adding a hostname field to the domain, i.e., the degenerate case where
  each domain only has one hostname)?  That is essentially what it would
  be doing?
  
thanx.

--  Kevin J. Ma

> -----Original Message-----
> From: HeXiaoyan [mailto:[e-mail]]
> Sent: Monday, October 17, 2011 3:14 AM
> To: Kevin J Ma; [e-mail]
> Subject: RE: [CDNi] CDNI Metadata Interface
> 
> 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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