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Re: Re[8]: [equinox-dev] OBR2


Peter, Jeff,

Groups have value, but they have problems. But I would like to make sure that we don't impose groups.
We may want to promote one model for groups, through tool support in Eclipse for e.g., but I don't feel
we are in a position to impose a concept of groups, nor that we have a good general solution.

First of all, even we would all agree that groups have value, we have different grouping models.
At least, Eclipse features and MEG deployment packages. I also know of Linux distribution
using RPM deployment to bring down plugins (after all, this is just about downloading files).
I don't think we are in any position to impose a grouping... You are right Peter, there is a lot
of semantics associated with grouping... and it is mostly a concern for packaging and
management tools.

As we all remember, grouping introduces many headaches, especially when sharing
between groups are entertained. Installing and uninstalling groups with non empty
intersections is tricky. As far as I know, no one has a decent and robust solution so far.
This is especially true because groups never stay simple about sets of bundles...
Sooner or later scripting appears... configuration data... etc...
It is the case for Eclipse and it is the case for MEG Deployment Packages...
Then groups get into fragments... and optional downloads based on environment variables...
because applications are formed out of different  configurations in different environments...
and this is not to consider different offerings (different prices for different configurations).

So it is hard to reason about groups in these contexts... to even predict if it can be installed or not.
Then again, you are right Peter... dependencies between groups open up again the semantic
question about flexibility (import-export versus provide-require). Usually dependencies are more like
provide-require... but we need the import-export flexibility... While for Java packages, we can
rely on the specification versus implementation semantics, this is no longer true for groups...

However, there are very good reasons for not using bundles instead of groups...
Admin granule is usually much larger than the runtime bundle granule...
You want to allow flexibility in the configuration of a product or a product suite...
You want fine-grain ability to update... fine-grain security control...
fine-grain lifecyle and lazy activation...

All of which demonstrates that the runtime modularity of a software does not match
very well the admin modularity of it... or its provisioning modularity...
Something that we should may think about more... :-)

But here is my point, we may allow groups... but it seems that we don't want to specify
them in the OSGi standard. In fact, I like that OSGi is mostly about runtime artifacts, and not
about provisioning. I would argue that we don't want to force the adoption of a group semantics.
I would argue that we need to fit in existing provisioning efforts... like JSR 124... or like OMA...

I would say that we need the following, just for bundles, without talking about groups.
We need to have a provisioning infrastructure for bundles, and bundle alone.
We need to be able to find where a bundle can be downloaded from (technically easy
but not that easy in practice to put in place...) We need to be able to override
a bundle's definition of its dependencies,  so to make it fit in a configuration
when provisioning it (a flexibility we don't have so far).
Above this layer, it should be easy to build the notion of groups, if one wants to.

There is a lot to do at the level of bundles alone...
We have to consider extensibility there for dependencies...
We already have import-export statements... and require-provide...
We also have declarative services... and extensions and extension points
(I know some people that may not want to deploy a plugin that provides extensions
to non-available extension points)...

I like the JSR 124 approach... where we talk about resources, providing and requiring capabilities.
The approach is extensible with the ability to define new capabilities... with new matching rules.
It would be interesting to see if we can model

        - RFC 79
        - SCR
        - extensions and extension points

What's missing I believe would be a discovery infrastructure...
mapping from capabilities to resources...
some of which will be OSGi bundles.... some of which may be other things.

I feel that OSGi provisioning needs to fit in a larger story that allows to deploy not only bundles...
I don't feel like we will be able to impose a unique grouping model... but through an open approach
we may allow OSGi to be a premier choice for Java component models.

Groups are surely important, and I would suggest that we promote one model through Eclipse

and a good tooling support... mostly as a proof that we can built it on top of the bundle-level
infrastructure... but I don't see why we would want the provisioning infrastructure to be imposing
a grouping model. Promote... but accomodate... in other words... apply modularity and flexibility
to our own designs and architectures... :-)

Best regards,

Olivier Gruber, Ph.D.
Persistent & Distributed Object Platforms and Frameworks
IBM TJ Watson Research Center




Peter Kriens <Peter.Kriens@xxxxxxxx>
Sent by: equinox-dev-bounces@xxxxxxxxxxx

09/29/2005 08:58 AM
Please respond to Equinox development mailing list

       
        To:        Jeff McAffer <Jeff_McAffer@xxxxxxxxxx>
        cc:        Equinox development mailing list <equinox-dev@xxxxxxxxxxx>
        Subject:        Re[8]: [equinox-dev] OBR2



I think this is the discussion require-bundle versus Import-Package
all over again ... :-)

a priori grouping will favor popular platforms until the extent that
there will be only one dominant platform because is too hard to
support all. (Law of increasing returns). E.g. Microsoft windows.
Without grouping I think it is easier for a management system to
compose a set that is needed, allowing third parties to provide the
glue components.

And I never understood why things are not just merged in a single
bundle if they really have to be together ...

The diversity of the embedded market requires imho a flatter model.
But then again, I guess I am only a theoretician :-(

Kind regards,

    Peter Kriens







JM> For the most part.  I believe that explicit groups are
JM> necessary.  It is natural to group things and then group the
JM> groups etc.  Doing this with queries is possible but ends up being
JM> roundabout.  Your point about explosion is valid but queries don't
JM> solve the problem. For example, who is going to manage the
JM> queries? How do I tell you about my group?  Do I send you my
JM> query?  What if someone adds something that matches the query but
JM> I did not intend for that to be part of the group?  How do you
JM> compose multiple query-based groups to make a composite group?

JM> Groups can be done in a way that allows you to have your
JM> groups and me to have mine.  We can share the group definitions if
JM> we want but do not have to.  If shared they can be inthe repo as
JM> first class enties.  They (perhaps) can be versioned and express
JM> dependencies of their own.

JM> Jeff



JM> Peter Kriens <Peter.Kriens@xxxxxxxx>
JM> Sent by: equinox-dev-bounces@xxxxxxxxxxx
JM> 09/25/2005 11:14 AM
JM> Please respond to
JM>  Equinox development mailing list

JM> To
JM> Jeff McAffer/Ottawa/IBM@IBMCAcc
JM> Equinox development mailing list <equinox-dev@xxxxxxxxxxx>Subject
JM> Re[6]: [equinox-dev] OBR2




JM> I think we agree ...

JM>  The repo metadata should have no semantic knowledge of its contents.
JM>  The requirements/capabilities should be generic. When you import you
JM>  translate the specific (import-package, require-bundle, scree=128x256,
JM>  etc) requirements to generics. This means that the repo does not need
JM>  to have semantic knowledge.

JM>  However, a group should be the result of a query and not explicitly
JM>  submitted to the repo. If you do that, you always end up in a
JM>  combinatorial explosion of groups. The diversity out there is so high
JM>  ... which en then usually means only 1 configuration is supported.
JM>  Works maybe for Windows, but OSGi needs something more flexible imho
JM>  because portability is at the root.

JM>  Kind regards,

JM>      Peter Kriens

JM>> Just to clarify what I after is not having to author two sets
JM>> of metadata.  From a repository USER's point of view I have a
JM>> bundle, I add it to the repo.  I need a bundle, I query the repo
JM>> and get the thing I need/want.  When adding a bundle to the repo
JM>> the repo itself should interrogate the bundle and find any
JM>> dependencies.  

JM>> There is a challenge in that there may be dependencies that
JM>> cannot be detected.  For example, we have this in our Help setup
JM>> where help needs an appserver.  Typically Tomcat is supplied but
JM>> there may well be others.  You would not want to spec help to
JM>> depend on Tomcat.  If we were using services then you would spec
JM>> Help to need the webapp service.  Perhaps when we have declarative
JM>> services that will be a possibility but there will still be such
JM>> scenarios where the public contract implied by services is not
JM>> appropriate and alternative mechanisms (e.g., the extension
JM>> registry) are used.

JM>> Grouping bundles is an interesting notion that solves this
JM>> issue as well as allows function producers to explicitly declare
JM>> sets of bundles that go together.  A bundle group can simply be
JM>> viewed as a bundle that aggregates the constituent parts.  However
JM>> it is actually represented it is just a unit that exports the
JM>> union of the exports in its contents and imports/required the
JM>> union of its prerequisites. etc.  

JM>> Expressing or representing these capabilties and requirements
JM>> in an an open, extensible way is goodness.

JM>> Jeff



JM>> Peter Kriens <Peter.Kriens@xxxxxxxx>
JM>> Sent by: equinox-dev-bounces@xxxxxxxxxxx
JM>> 09/23/2005 12:16 PM
JM>> Please respond to
JM>>  Equinox development mailing list

JM>> To
JM>> Thomas Watson <tjwatson@xxxxxxxxxx>cc
JM>> Equinox development mailing list
JM>> <equinox-dev@xxxxxxxxxxx>, heavy@xxxxxxxxxxxxxxxxxxxxx
JM>> Re[4]: [equinox-dev] OBR2




JM>> Good idea, but I assume it can be used to generate the meta data?

JM>>  I think this is an example where the generic requirements capability
JM>>  model shines. We will have lots of dependencies that need to be
JM>>  modeled. Modeling them semantically in the repo format will make the
JM>>  repo format a major spec work undertaking.

JM>>  Kind regards,

JM>>      Peter Kriens

TW>>> Can we use SCR's component XML definition for service
TW>>> dependancies?  Even if the bundle does not use SCR directly can we
TW>>> still use this schema to define service dependancies?  I would not
TW>>> want to define a whole new schema for this.

TW>>> Richard, are you subsribed the the equinox-dev mailing list?
TW>>>  If not, please do so we don't have to keep cc'ing you on the
TW>>> mails :)

TW>>>  Thomas Watson
TW>>>  Pervasive Development
TW>>>  Phone: 512-838-4533 Tie: 678-4533
TW>>>  tjwatson@xxxxxxxxxx


TW>>> equinox-dev-bounces@xxxxxxxxxxx wrote on 09/23/2005 08:34:11 AM:

>>>> Agree ... if it is not in the manifest, we can't generate it. But it
>>>> is nice to populate a repo with only the data from the manifests and
>>>> get reasonable results.
>>>>
>>>> Kind regards,
>>>>
>>>>      Peter Kriens
>>>>      
>>>> RSH> Peter Kriens wrote:
>>>>
>>>> >>It absolutely MUST be possible to generate the metadata from the
>>>> >>manifest.
>>>> >>  
>>>> >>
>>>>
>>>> RSH> Well, it is not possible given the current state of bundle manifests to
>>>> RSH> generate all repository metadata. For example, there is no way to
>>>> RSH> generate service dependencies.
>>>>
>>>> RSH> If someone invents a new capability/requirement pair, there will be no
>>>> RSH> way to generate it either.
>>>>
>>>> RSH> For the standard package/module-related stuff, we can generate them from
>>>> RSH> the manifest.
>>>>
>>>> ->> richard
>>>>
>>>> RSH> _______________________________________________
>>>> RSH> equinox-dev mailing list
>>>> RSH> equinox-dev@xxxxxxxxxxx
>>>> RSH> https://dev.eclipse.org/mailman/listinfo/equinox-dev
>>>>
>>>>
>>>> --
>>>> Peter Kriens                              Mob +33633746480
>>>> 9C, Avenue St. Drézéry                    Tel +33467542167
>>>> 34160 Beaulieu, France                    Tel +15123514821
>>>>                                           Tel +33870447986
>>>> AOL,Yahoo, Skype pkriens                  ICQ 255570717
>>>>
>>>> _______________________________________________
>>>> equinox-dev mailing list
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>>>> https://dev.eclipse.org/mailman/listinfo/equinox-dev
JM>>   


JM>>  --
JM>>  Peter Kriens                              Mob +33633746480
JM>>  9C, Avenue St. Drézéry                    Tel +33467542167
JM>>  34160 Beaulieu, France                    Tel +15123514821
JM>>                                           Tel +33870447986
JM>>  AOL,Yahoo, Skype pkriens                  ICQ 255570717

JM>>  _______________________________________________
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JM>>  https://dev.eclipse.org/mailman/listinfo/equinox-dev

JM>   


JM>  --
JM>  Peter Kriens                              Mob +33633746480
JM>  9C, Avenue St. Drézéry                    Tel +33467542167
JM>  34160 Beaulieu, France                    Tel +15123514821
JM>                                           Tel +33870447986
JM>  AOL,Yahoo, Skype pkriens                  ICQ 255570717

JM>  _______________________________________________
JM>  equinox-dev mailing list
JM>  equinox-dev@xxxxxxxxxxx
JM>  https://dev.eclipse.org/mailman/listinfo/equinox-dev

 


--
Peter Kriens                              Mob +33633746480
9C, Avenue St. Drézéry                    Tel +33467542167
34160 Beaulieu, France                    Tel +15123514821
                                         Tel +33870447986
AOL,Yahoo, Skype pkriens                  ICQ 255570717

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