Subject: Inheritance on properties

From: Bita Shadgar <[email-masked]>
Date: Sun, 26 Aug 2001 19:34:37 +0100

Hi,
I am wondering if anybody let me know, has the inheritance been
considered on properties of resources in Webdav?

Consider you have  a lots of resource with the same properties. If you
have inheritance, you can
easily store one copy of properties and it can be inherited to other
resources with the same properties.

Indeed, what is preparationed in Webdav if a resource has a property
with more than one value. I know it is considered in RDF, however I
think it may be necessary to be a part of Webdav. So that all Webdav
projects support it intrinsically.  What do you think?

Any discussion  and pointer will be appreciated,
Bita.

---

From: "Jim Whitehead" <[email-masked]>
Date: Mon, 27 Aug 2001 11:40:25 -0700

> considered on properties of resources in Webdav?

I don't think we ever considered this idea.  The access control
specification has inheritance of access control lists, which are represented
as properties, but this capability is limited just to access control lists.

> resources with the same properties.

Some issues here:

* Is the inheritance down a collection hierarchy (from a collection to its
members), or up a hierarchy (from a member to its parents), or does there
need to be a mechanism for specifying the inheritance pattern?

* Which takes precedence, the inheritance operation, or a lock? That is, if
A inherits properties from B, and A is locked, what is the effect of a
PROPPATCH on B? Does it succeed, or does it fail, due to the lock on A?

> projects support it intrinsically.  What do you think?

We left this up to the definition for each individual property.  There are
many ways to represent this.

For example:

<authors>
  <author>...</author>
  <author>...</author>
  ...
</authors>

or

<author>
  <elem1>...</elem1>
  <elem2>...</elem2>
  ...
</author>

or

<author>
  <list>
    <li>...</li>
    <li>...</li>
    ...
  </list>
</author>

- Jim

---

From: "Julian Reschke" <[email-masked]>
Date: Mon, 27 Aug 2001 21:23:45 +0200

> many ways to represent this.

This could be implemented using typed properties: Although my proposal (see
<http://www.greenbytes.de/tech/webdav/draft-reschke-webdav-property-datatype
s-00.html>) currently doesn't give an example for this case, this could for
instance be implemented using SOAP's array encoding scheme (indeed our
server implements this).

---

From: "Dylan Barrell" <[email-masked]>
Date: Mon, 27 Aug 2001 15:38:17 -0400

There is nothing in webDAV that precludes a server from implementing this
inheritance under the covers.

That having been said, I would like to see the spec extended to support
schema discovery resources and would not be opposed to an optional portion
of the spec dealing with inheritance.

The biggest problem with the current spec and its usage in the real world is
that properties are essentially useless other than as a way for a particular
client implementation to store attributes that another instance of the same
client would then be able to re-use. There is no way for the server to tell
the client what properties it requires and the type of those properties (for
example it should be possible for a collection to enforce a mandatory expiry
date to be provided for each new document added to that collection) the
client should be able to identify that the collection requires this
property, that it is a date property so that an appropriate interface can be
presented to the user for capture of the date.

This means that if you have multiple interfaces to the same repository
(webDAV, web, proprietary client, wireless), there is no meaningful way for
them to interoperate on properties with standard webDAV clients.

--Dylan

> -----Original Message-----
> From: [email-masked]
> [mailto:[email-masked]]On Behalf Of Jim Whitehead
> Sent: Monday, August 27, 2001 2:40 PM
> To: WebDAV
> Subject: RE: Inheritance on properties
>
>
> Bite Shadgar writes: