RE: [fractal] Re: [architecture] Fractal packaging & deployment, bis

[mathieu.vadet@xxxxxxxxxxxxxxxxxx]

Hi all,

I agree with Jose, I don't see how "containment and binding" constraints
will apply to system dependencies

If we take the rich example of the CCM, then we can see in the software
component desriptors  the following dependencies:

 - what you call "binding" dependencies, ie functional dependencies (I need
interface Itf to work)

 - container dependencies, ie dependencies against technical services (I
need TX_NEVER policy on operation do_it of interface Itf, for transactions)

 - system dependencies, ie dependencies against the OS, libraries, etc (I
need the libfoo.so, I need Linux 2.4.18 kernel)

Please note that the last dependency can't be considered as "binding"
dependencies, except if the "feature" is wrapped by a fractal component; but
then you'll have to wrap many system features 

I feel that there's some elements missing:
  - system dependencies description in metadata

  - container dependencies description in metadata (but in the case of
fractal, maybe they can be described as "binding" dependencies)

  - conflict management, because you may not be able to describe any system
dependency in a standard way (used in any package), therefore, you may not
be able to discover all conflicts automatically from the metadata, and you
may be forced to explicitely state these conflicts

hope it helps
Mathieu

> 
> At 17:05 +0200 11/05/04, Jose Luis Ruiz Revuelta wrote:
> >El mar, 11-05-2004 a las 09:29, Eric Bruneton escribió:
> >>  Richard S. Hall wrote:
> >>  > This really depends on whether the purpose is to create a
> >>  > deployment infrastructure for deploying Fractal-based 
> applications
> >>  > or if the purpose is to create a more general 
> deployment middleware
> >>  > (at least for Java), where Fractal-based applications 
> are just one
> >>  > type of application to be deployed.
> >>  >
> >>  > If the purpose is only for Fractal-based applications 
> and the only
> >>  > types of dependencies that exist among "packages" are
> >>  > component-oriented dependencies (i.e., containment and binding),
> >>  > then it probably doesn't make a difference what you call it.
> >>
> >>  I hope it will be possible to create a deployment 
> infrastructure for
> >>  deploying Fractal-based applications that can also deploy 
> arbitrary
> >>  (Java and non Java) applications. This is not 
> contradictory: it just
> >>  imply that arbitrary applications can be seen as Fractal-based
> >>  applications (and this should be possible since the 
> Fractal model is
> >>  modular, extensible, and not tied to Java; for example, plain old
> >>  Java objects are compliant with Fractal level 0). Or, in 
> other terms,
> >>  that existing packaging formats can be seen as Fractal 
> packages (and,
> >>  in particular, that their dependencies can be seen as Fractal
> >>  "containment and binding" dependencies - hence this mail
> >>  
> http://www.objectweb.org/wws/arc/fractal/2004-05/msg00005.html). Or,
> >
> >Ummmm, are you sure that "contaiment and binding" dependencies are
> >expresive enough to represent all kinds of dependencies for existing
> >packaging formats?
> >
> >For example, in Debian, package metadata explicitly consider 
> conflicts
> >between packages. How can contaiment and binding 
> dependencies be used to
> >describe conflicts between packages?
> >
> >Sometimes due to any reason two existing packages can not live
> >together(for example, both packages access a resource that can not be
> >shared), in other words, are incompatible. I feel that conflict
> >management is an important aspect in order to keep the 
> consistency and
> >the stability of an execution environment.
> >
> >Regards,
> >Jose
> >
> >
> >
> 
> It depends in large part of what you mean by 
> 'package metadata exlicitly consider conflicts'. 
> If you have a component which enforces as a 
> policy to be bound at most once in any point in 
> time, you have in effect a non-sharable 
> component. Documenting a dependency by means of a 
> binding towards this component means that you 
> must follow the binding policy for this component 
> and, in this particular case, successfully deploy 
> your package if the referenced package is not 
> already bound. A binding in Fractal can have a 
> very rich (or complicated) semantics. To 
> determine if the approach Eric has outlined is 
> feasible or not, we need to assesss the nature of 
> the dependencies betwen 'deployment units' used 
> in existing systems.
>