Re: [netmod] initial comments on draft-rwilton-netmod-yang-packages

[Robert Wilton <[e-mail]>]

On 30/01/2019 20:51, Andy Bierman wrote:
>
>
> On Wed, Jan 30, 2019 at 10:04 AM Robert Wilton <[e-mail] 
> <mailto:[e-mail]>> wrote:
>
>
>     On 30/01/2019 17:31, Andy Bierman wrote:
>>
>>
>>     On Wed, Jan 30, 2019 at 8:02 AM Robert Wilton <[e-mail]
>>     <mailto:[e-mail]>> wrote:
>>
>>
>>         On 30/01/2019 15:16, Andy Bierman wrote:
>>>
>>>
>>>         On Wed, Jan 30, 2019 at 4:19 AM Robert Wilton
>>>         <[e-mail] <mailto:[e-mail]>> wrote:
>>>
>>>             Hi Andy,
>>>
>>>             Thanks for the comments.
>>>
>>>             On 30/01/2019 01:22, Andy Bierman wrote:
>>>>             Hi,
>>>>
>>>>             I originally brought up this issue in July 2015
>>>>             https://datatracker.ietf.org/doc/draft-bierman-netmod-yang-package/
>>>
>>>             Yes.
>>>
>>>             The solution I propose is different in the sense that it
>>>             uses YANG instance data to define YANG packages rather
>>>             than new YANG keywords.   I believe that this should
>>>             make it a lower cost solution to define and implement.
>>>
>>>
>>>
>>>         I think yangvalidator.org <http://yangvalidator.org> has a
>>>         better solution that does not change YANG conformance.
>>
>>         Do you mean that we can just use zip files with the list of
>>         modules?
>>
>>
>>     I don't care about the solution details yet. They are 2nd order
>>     problems.
>>
>>     Conformance means "what modules are required to be implemented
>>     together".
>>     It is not clear that this problem can be solved.  The
>>     augment-stmt defines implicit
>>     multi-module conformance.  I am not convinced that the extra work
>>     of defining package conformance
>>     is worth it.
>
>     So, I'm not proposing backing any sort of package conformance into
>     the language at all.  A package is just metadata that defines that
>     a set of modules, at particular revisions/versions, work together
>     and can represent part of a YANG schema.
>
>     This is equivalent to
>      - how a zip file of YANG modules provided to yangvalidator would
>     work.
>      - getting the contents of YANG library from a server (but a YANG
>     packages soln can also work offline)
>      - fetching the modules from YANG catalog (if they have been
>     labelled appropriately), although I'm not convinced that this
>     universally works today.
>
>
> This sort of metadata could be provided by module tags.
> A vendor or SDO could define module-tags that represent packages.

Yes, this is a different way to assigning membership, although I'm not 
convinced that it is better.

I think that such a scheme could work without versioning, but I'm not 
sure that it will work so well once package versioning is considered, 
because to handle versioning the tags don't just need to represent which 
package they belong to, they also should identify which version of that 
package.

E.g. [e-mail] might be tagged with:
"ietf-base-pkg@0.0.1", "ietf-base-pkg@0.0.2", "ietf-base-pkg@1.0.0", 
ietf-base-pkg@1.1.0", ...

If packages change quite frequently then you might find that a module 
needs 50+ tags to identify which particular packages it belongs to.

Any without knowing the package version, I don't see that there would be 
enough information to build a schema since you wouldn't know which 
versions of YANG modules to use.


>
>
>     But in terms of the usability of YANG, I don't think that doing
>     conformance only at the module level is really sufficient. 
>     Clients need to be coding against sets of modules at particular
>     versions that are known to work together, and known that multiple
>     server vendors will implement.
>
>     A pick and mix appropriate to module revisions doesn't seem to
>     help anyone.
>
>
>
> I get all the different components and variables one might have for a 
> package.
> I am not as convinced (as in 2015) that standard packages could be 
> simple and widely deployed..
> Now it seems vendors implement an ad-hoc subset + additions to everything.
> It doesn't help to define a new package variant to match the vendor 
> implementation.
> The YANG library can do that already.

YANG library is only on the box at the moment, and it just gives a flat 
list of modules.
I would like it to also be available off the box and have more structure.

E.g. I would like IETF to define an L2VPN package that contains the 
basic set of YANG modules that a device that supports L2VPN services 
would be expected to implement at a minimum.

Then, rather that checking the output of YANG library to see that it has 
all the necessary modules to implement an L2VPN service, I could instead 
check whether the package implemented by the device imports the L2VPN 
package.  And if it does import that package, I can then also see which 
version of that package it implements (rather than checking every module 
version).

>
> You seem more optimistic than me that the industry is actually ready, 
> willing, and able
> to implement standard YANG packages.

If we want YANG to be properly successful then I see that it has go 
there.  But nobody can do this today until there is a way that such 
packages can be defined, and versioned, and we start defining what these 
standard packages look like.


>
>
>
>>
>>     The issue of what modules does vendor A implement is not a
>>     conformance problem.
>>     It is just more metadata and YANG Catalog is focused on providing
>>     that data.
>
>     Does YANG catalog indicate the set of IETF modules that I would
>     need to implement L2VPN services on a device?
>
>
> This seems like a separate problem, but actually it can help by 
> searching a lot of known modules.
> In order to know what vendor A, B, and C have in common, you need to 
> get the catalog info for each vendor.
>
> Module tags can also solve this problem.

But when there are multiple vendors with multiple devices, with multiple 
versions of software available then this looks like a hard problem to solve.

I would like someone (or a program) to be able to look at a package 
definition file, and determine if it implements what is required, and 
what software version is needed, and whether they are deviations that 
matter.

When my client then connects to that device, I would like the client to 
be able to check that it implements that modules that I expect it to.  I 
would strongly prefer if this could be done by returning a small amount 
of data, rather than a list of 1000 modules/sub-modules for every server 
that I connect to.

Module tags won't tell the client that it implements all the required 
modules that implement the L2VPN service, it will just indicate that 
implements some modules which can be used to implement an L2VPN service.


>     Module tags could be used to do this (another packaging solution),
>     but this would cause a proliferation of tags when it comes to
>     versioning, since I don't think that you can cleanly bake semver
>     into module tags.
>
>
>>
>>         I don't really see how this helps.
>>
>>         Consider:
>>         - server vendor A, implements some subset of the OpenConfig
>>         YANG modules, each at a particular version, along with some
>>         deviations and vendor augmentations.
>>         - server vendor B, implements the same subset of the
>>         OpenConfig YANG modules, but at different versions, along
>>         with some deviations and vendor augmentations.
>>         - server vendor C, implements a slightly different set of the
>>         OpenConfig YANG modules, but at different versions, along
>>         with some deviations and vendor augmentations.
>>
>>         As a client, how do I know what module versions to code
>>         against, when I want to work with devices provided by all
>>         three vendors?
>>
>>
>>
>>     The vendors publish their implementation details on yangcatalog
>>     and you get the info
>>     and see what modules are in common.
>>
>>     There are only market requirements determining what group of
>>     modules has to exist
>>     in an implementation.  It is not clear to me that formalizing
>>     these requirements
>>     is something the industry will do effectively. Module tags
>>     already provide a way
>>     to conceptually group modules together.
>>
>>     Seems like every vendor has openconfig, foo-openconfig, and
>>     foo-openconfig-deviations
>>     so that there are no agreed upon subsets. Even if openconfig had
>>     properly documented
>>     subsets, would your client even be able to code to it (ignoring
>>     add-ons and deviations).
>
>     I think that answer will converge on yes, I don't know how long it
>     will take.  It would probably be better if at the time that
>     protocol specifications are written, that the authors of the
>     specifications also write the YANG modules to manage them at the
>     same time.
>
>>
>>         I might be wrong, but I think that the OC solution is use git
>>         tags, so they tag sets of modules that are expected to work
>>         together and also to provide a linear release history of
>>         their sets of modules.  So, if everyone implements the module
>>         versions associated with a git tag then it should convert a
>>         two dimensional problem of module revisions into a linear
>>         problem.  The YANG packages draft is aiming to provide a
>>         solution to this problem that doesn't require the use of git,
>>         or sending zip files of modules around.
>>
>>
>>         At the moment, it seems that everyone is doing this in
>>         different ways:
>>          - Yumawork customers/servers use zip files of modules for
>>         conformance.
>>
>>
>>     Not sure what this means.
>>     Actually the server libraries can be loaded and unloaded.
>>     Module can be standalone libraries or grouped as bundles.
>>     But this seems like an implementation detail, unrelated to
>>     conformance.
>>
>>
>>          - OpenConfig client/server implementations use git tags, or
>>         git refpoints.
>>          - Cisco customers use the contents of directories on github
>>         YangModels.
>>
>>         Finally, this draft doesn't change YANG conformance, it just
>>         expresses it in what is intended to be a simpler way.
>>
>>
>>     It adds another conformance system to maintain.
>>     The language only recognizes module to module interfaces, not
>>     package to package.
>
>     I propose that at the language level conformance is at the module
>     level (modulo import-by-version).
>
>
>>     That adds more complexity. It doesn't take away any complexity.
>
>     It is meant to be a simpler way of packaging up, and trying to
>     control and manage the complexity that already exists today.
>
>     E.g. I could give a YANG compiler the name, version, and location
>     of a package and tell it to build the entire schema associated
>     with that package.
>
>
> This is a tool implementation detail, not a conformance issue.
> It would be nice to have a standard format for the YANG library for a 
> tool to use.
> You seem to be proposing an artifact containing ietf-yang-library 
> information.
> That seems OK to me, but it should not have anything to do with 
> conformance.
> It is just a standard way to express a module-set in a yang-data artifact.

Yes, what I am proposing is close to a file containing ietf-yang-library 
information, but I want it to be hierarchical/recursive, where as the 
schema defined by YANG library bis is flat, and I want the data to also 
optionally be made available in YANG library.

What I am proposing here doesn't change conformance of the YANG language 
in any way, not does it replace YANG library.

Thanks,
Rob


>
>
>     In a somewhat similar way, when I write code, my build file
>     specifies which libraries I depend on, and their versions, but I
>     can leave it to the build tool to determine what those libraries
>     themselves depend on and recursively pull in all the dependencies.
>
>
>>
>>     If there was a standard to load and unload modular functionality
>>     at boot-time or run-time,
>>     then I could see why there is a need to have a standard to define
>>     YANG packages.
>
>     I agree that this is another example of where they could be useful.
>
>     Thanks,
>     Rob
>
>
>
> Andy
>
>>
>>         Thanks,
>>         Rob
>>
>>
>>
>>     Andy
>>
>>>
>>>
>>>         Andy
>>>
>>>>
>>>>             I don't think the WG ever agreed on the problem that
>>>>             needs to be solved,
>>>>             and that is still the case.
>>>
>>>             That wasn't quite my impression.  I also think that
>>>             folks were busy focusing on other WG activity and didn't
>>>             necessarily have the time to concentrate on this.
>>>
>>>             My draft was aiming on solving two broad problems:
>>>
>>>                 The main goals of YANG package definitions include, but are not
>>>                 restricted to:
>>>
>>>                 o  To act as a simplified YANG conformance mechanism.  Rather than
>>>                    conformance being performed against a set of individual YANG
>>>                    module revisions, conformance could also be more simply stated in
>>>                    terms of YANG packages, with a set modifications (e.g. additional
>>>                    modules, deviations, or features).
>>>
>>>                 o  To allow YANG datastore schema to be specified in a more concise
>>>                    way rather than having to list all modules and revisions.  YANG
>>>                    package definitions can be defined in documents that can be
>>>                    referenced by a URL rather than requiring explicit lists of
>>>                    modules to be shared between client and server.  Hence, a YANG
>>>                    package must contain sufficient information to allow a client or
>>>                    server to precisely construct the schema associated with the
>>>                    package.
>>>
>>>
>>>
>>>>
>>>>             In reality each server has 1 package -- its entire library.
>>>
>>>             This doesn't apply to all servers. For a long time, as a
>>>             vendor, we have had separate packages that can be
>>>             independently installed, and which extend the management
>>>             model to cover the new functionality.  E.g. BNG
>>>             functionality could be in a separate, independently
>>>             installable, package on top of the base router
>>>             functionality.
>>>
>>>             For a Linux server, the manageability interface will
>>>             depend on what applications have been installed.
>>>
>>>
>>>>             The SEMVER work shows
>>>>             that vendors are treating platforms as independent
>>>>             release trains, and not really
>>>>             developing loadable packages.
>>>
>>>             This depends on the vendor.  The YANG versioning work is
>>>             trying to find a solution that works across the
>>>             industry.  I believe that the versioning requirements
>>>             are different for standards developed modules, vs
>>>             industry developed modules, vs vendor modules.
>>>
>>>
>>>>
>>>>             I think YANG 1.2 improvements for conformance (e.g.,
>>>>             YANG-redirects, SEMVER import)
>>>>             and  the YANG Catalog can solve the module
>>>>             compatibility issues. It is more of a documentation
>>>>             problem than a standards problem.
>>>
>>>             Having a standard YANG module that can be used to define
>>>             packages is something this is useful and should be
>>>             standardized.  I believe that this is better than each
>>>             vendor coming up with their own solution for this problem.
>>>
>>>             Thanks,
>>>             Rob
>>>
>>>
>>>>
>>>>
>>>>             Andy
>>>>
>>>>
>>>>
>>>>
>>>>             On Tue, Jan 29, 2019 at 4:55 PM Sterne, Jason (Nokia -
>>>>             CA/Ottawa) <[e-mail]
>>>>             <mailto:[e-mail]>> wrote:
>>>>
>>>>                 Thanks Rob. Please see inline.
>>>>
>>>>                 Jason
>>>>
>>>>                 *From:*Robert Wilton <[e-mail]
>>>>                 <mailto:[e-mail]>>
>>>>                 *Sent:* Thursday, January 24, 2019 1:16 PM
>>>>                 *To:* Sterne, Jason (Nokia - CA/Ottawa)
>>>>                 <[e-mail]
>>>>                 <mailto:[e-mail]>>; [e-mail]
>>>>                 <mailto:[e-mail]>
>>>>                 *Subject:* Re: initial comments on
>>>>                 draft-rwilton-netmod-yang-packages
>>>>
>>>>                 Hi Jason,
>>>>
>>>>                 Thanks for the review and comments.
>>>>
>>>>                 I've put some responses inline ...
>>>>
>>>>                 On 24/01/2019 14:56, Sterne, Jason (Nokia -
>>>>                 CA/Ottawa) wrote:
>>>>
>>>>                     Hi guys,
>>>>
>>>>                     I've gotten most of the way through the draft
>>>>                     and have some initial comments. I haven't
>>>>                     digested the section 10 open issues yet or the
>>>>                     examples.
>>>>
>>>>                     Section 5 mentions the following:
>>>>
>>>>                        YANG library is augmented to allow servers
>>>>                     to report the packages
>>>>
>>>>                        that they implement and to associate those
>>>>                     packages back to
>>>>
>>>>                        particular datastore schema.
>>>>
>>>>                     Does the combination of this draft and
>>>>                     rfc7895bis somehow allow the same package to be
>>>>                     advertised in 2 different datastores, but with
>>>>                     different deviations in each datastore? I'm
>>>>                     thinking of a case, for example, where a
>>>>                     package is fully supported in the running but
>>>>                     the package minus a few modules (or parts of
>>>>                     modules) is supported in the operational
>>>>                     datastore. There seems to be a 1:1 relationship
>>>>                     between package and rfc7895bis schema.
>>>>
>>>>                 So, the intention is no, not directly.
>>>>
>>>>                 My aim here is that <running> would implement
>>>>                 package "foo", and <operational> would implement
>>>>                 package "modified-foo".  Package "modified-foo"
>>>>                 would import package "foo" and also specify the set
>>>>                 of modules that contain the deviations "foo".
>>>>
>>>>                 I didn't want a server to be able to see that I
>>>>                 implement package "foo", but then I have all these
>>>>                 deviations that change its behavior. Instead, it is
>>>>                 really implementing a different package that is
>>>>                 based on "foo".
>>>>
>>>>                     The packages draft doesn't include any specific
>>>>                     leaf-list for deviations. Section 7.2 mentions
>>>>                     that deviations could be expressed by including
>>>>                     modules that happen to contain deviations. That
>>>>                     seems a bit inconsistent with rfc7895bis that
>>>>                     has a specific leaf-list of deviations (and
>>>>                     NETCONF hello that specifically explicitly
>>>>                     labels deviation modules).
>>>>
>>>>                 I'm conflicted on this one.  I don't really like
>>>>                 the deviation list in YANG library because I regard
>>>>                 it as a duplicate source of information, and then
>>>>                 there is a question of which source of data do you
>>>>                 trust.  E.g. do you process a deviation in a module
>>>>                 that is not listed in the deviations module list?
>>>>
>>>>                 */[>>JTS: ] Good point. I suppose this issue
>>>>                 applies today already. i.e. what if one of the
>>>>                 modules advertised in the <hello> is a module of
>>>>                 deviations (without having been referenced by
>>>>                 another module as a deviation module)./*
>>>>
>>>>                     Section 5.1 says the package must be
>>>>                     referentially complete. I can see the
>>>>                     advantages of that although wondering if that
>>>>                     might limit flexibility of partitioning modules
>>>>                     into packages. I could imagine use cases for
>>>>                     dividing a large set of modules into a few
>>>>                     packages that might rev independently but can
>>>>                     still all work together (especially if they rev
>>>>                     in a bc manner). But maybe that just starts to
>>>>                     introduce too much complexity?
>>>>
>>>>                 Yes, having partial packages may be useful. Perhaps
>>>>                 just adding a leaf to indicate whether a package is
>>>>                 referentially complete could be the answer here.
>>>>
>>>>                     I didn't understand this part of section 5.1.
>>>>                     Can you maybe illustrate with an example?
>>>>
>>>>                           The version/revision of a module listed
>>>>                     in the package module list
>>>>
>>>>                           supercedes any version/revision of the
>>>>                     module listed in a imported
>>>>
>>>>                           package module list.  This allows a
>>>>                     package to resolve any
>>>>
>>>>                           conflicting implemented module
>>>>                     versions/revisions in imported
>>>>
>>>>                           packages.
>>>>
>>>>                 Probably best to see example B.3. in the appendix
>>>>                 because it exactly illustrates this point.
>>>>
>>>>                 Basically:
>>>>                 1) Packages must explicitly list all versions of
>>>>                 all modules they define/import.
>>>>                 2) If two imported packages define different
>>>>                 versions of modules, then the package that is
>>>>                 importing them needs a way to define which version
>>>>                 to use.
>>>>                 3) A package needs a way to override the version of
>>>>                 module specified in an imported package.
>>>>
>>>>                 */[>>JTS: ] Thx. That example does help. I suppose
>>>>                 the designer of the package needs to carefully
>>>>                 check that the version they select can be
>>>>                 successfully used by all the modules in the package. /*
>>>>
>>>>                 */I think there is a minor typo in example B.3. 
>>>>                 The example-3-pkg is importing "/*
>>>>                 */example-import-1" but I believe you meant "/*
>>>>                 */example-import-1-pkg" (and some for import-2)./*
>>>>
>>>>                     It might be a good idea to add a parent-version
>>>>                     to the package module (to allow tracking
>>>>                     lineage of packages).
>>>>
>>>>                 Agreed, or maybe allowing a revision history like
>>>>                 modules. Not sure which is better here.  Packages
>>>>                 could get a lot of updates, and a long revision
>>>>                 history would not be helpful at all.
>>>>
>>>>                 */[>>JTS: ] I think a minimum of just specifying
>>>>                 the direct parent is enough to build the full tree
>>>>                 of lineage. We don't need a long history of N
>>>>                 revisions./*
>>>>
>>>>                     I like the use of groupings. That allows a
>>>>                     manager to use this as a building block to
>>>>                     compose a model that has a list of packages.
>>>>
>>>>                 OK.
>>>>
>>>>                     Having a global list of mandatory features (vs
>>>>                     having the mandatory feature a per-module list)
>>>>                     means inventing the new <module-name>:<feature>
>>>>                     format. Should we instead somehow put the
>>>>                     mandatory features against each module of the
>>>>                     package?
>>>>
>>>>                 Perhaps.  My thinking here was to have the list of
>>>>                 features high up and very easy to find/parse.
>>>>
>>>>                     The location leaf is a uri but then the
>>>>                     description says it must be a url (where the
>>>>                     model can be retrieved). I do like that the
>>>>                     namespace is separate from the location, but
>>>>                     maybe we should make location a url type?
>>>>
>>>>                 Yes, I was thinking that is should be a URL.
>>>>
>>>>                     Do we need a namespace for package names in the
>>>>                     model?
>>>>
>>>>                 I had them in an earlier version, but I took them
>>>>                 out, because I wasn't sure that they are really
>>>>                 useful/required.
>>>>
>>>>                 Defining a format to make package names themselves
>>>>                 globally unique might be sufficient.
>>>>
>>>>                 */[>>JTS: ] I'm OK with that. It is similar to how
>>>>                 we're finding that it is useful that YANG module
>>>>                 names are globally unique (i.e. by naming with
>>>>                 ietf-xxxx or companyabc-xxx)./*
>>>>
>>>>                     In 7.3 we only reference module-sets and not
>>>>                     modules. So the grouping of modules into sets
>>>>                     and packages must be the same?
>>>>
>>>>                 Not necessarily.
>>>>
>>>>                 I am trying to reuse the module-set definitions as
>>>>                 much as possible (to avoid duplication).  One issue
>>>>                 here is that module-sets are combined then all the
>>>>                 modules must not overlap, which doesn't make the
>>>>                 mapping to module-sets quite so clean.
>>>>
>>>>                     A schema can only have a single package. I
>>>>                     think that works but it means a server would
>>>>                     advertise multiple schemas if it wants to
>>>>                     support multiple packages. I'm not sure if
>>>>                     there are some downsides to that (it just
>>>>                     surprised me).
>>>>
>>>>                 My aim here was:
>>>>                  - multiple packages are advertised in
>>>>                 yang-library/packages
>>>>                  - datastores only report that they "implement" one
>>>>                 [top level] package version. [The package itself
>>>>                 might import other packages.]
>>>>
>>>>                 If we do package selection, then for a given YANG
>>>>                 client session, and the version of YANG library
>>>>                 available/reported by that session, it would appear
>>>>                 as if the server only implements one top level
>>>>                 package for a datastore.  Different clients
>>>>                 choosing different versions would see slightly
>>>>                 different output depending on which package version
>>>>                 they had selected to use.
>>>>
>>>>                 Thanks again for the review and the comments!
>>>>
>>>>                 Rob
>>>>
>>>>                     Jason
>>>>
>>>>                     *From:*netmod <[e-mail]>
>>>>                     <mailto:[e-mail]> *On Behalf Of
>>>>                     *Robert Wilton
>>>>                     *Sent:* Thursday, December 20, 2018 12:45 PM
>>>>                     *To:* [e-mail] <mailto:[e-mail]>
>>>>                     *Subject:* [netmod] YANG Packages
>>>>
>>>>                     Hi,
>>>>
>>>>                     I've written up an ID for a potential solution
>>>>                     for YANG packages using instance data:
>>>>
>>>>                     Abstract
>>>>
>>>>                        This document defines YANG packages, an
>>>>                     organizational structure
>>>>
>>>>                        holding a set of related YANG modules, that
>>>>                     can be used to simplify
>>>>
>>>>                        the conformance and sharing of YANG schema. 
>>>>                     It describes how YANG
>>>>
>>>>                        instance data documents are used to define
>>>>                     YANG packages, and how the
>>>>
>>>>                        YANG library information published by a
>>>>                     server can be augmented with
>>>>
>>>>                        additional packaging related information.
>>>>
>>>>                     https://datatracker.ietf.org/doc/draft-rwilton-netmod-yang-packages/
>>>>
>>>>                     Potentially this work may be of use as part of
>>>>                     the YANG versioning design team work.  In
>>>>                     addition, if the WG likes this approach of
>>>>                     defining YANG packages, then it might also be
>>>>                     useful to bind a schema to a YANG instance data
>>>>                     document.
>>>>
>>>>                     Some questions for members of the WG:
>>>>
>>>>                     1) Do members of the WG agree that YANG
>>>>                     packages is something that needs to be solved?
>>>>
>>>>                     2) Is the approach in this draft of defining
>>>>                     these as instance data documents a good
>>>>                     starting point?
>>>>
>>>>                     3) This approach augments YANG library-bis,
>>>>                     reusing module-sets, but not replacing the way
>>>>                     that modules are reported in YANG library-bis. 
>>>>                     Is this the right approach?  This approach
>>>>                     tries to allow module-sets to be reused for
>>>>                     both schema and packages, but the YANG
>>>>                     library-bis rules for combining module-sets
>>>>                     (i.e. no conflicts) may make this harder to
>>>>                     really reuse the module-sets for both purposes.
>>>>
>>>>                     Of course, any other comments or feedback is
>>>>                     welcome and appreciated.
>>>>
>>>>                     Thanks,
>>>>                     Rob
>>>>
>>>>                 _______________________________________________
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>>>>