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Re: [p2-dev] P2 default fragment requirements

Hi Daniel,

thanks for the response! In this particular case, though, I don't see what will break if <requires> is simply removed from
default fragment?


On 28.02.2014 11:53, Krzysztof Daniel wrote:
thanks for your questions.

Regarding http://wiki.eclipse.org/Equinox/p2/P2_Fragments - the name is unfortunate. It's a secondary mechanism for assembling installation
from "Installation Fragments". I expect you have no interest in it.

I think that the main reason you have hostRequirements and requires are because hostRequirements are usually smaller than required.
hostRequirements says where to attach the fragment, and required means what the fragment needs.

They are identical because P2 will minimize the installation, hence the same bundle used in hostRequirements will be used for satisfying
requires. I think the protocol could be improved here, but there is almost no gain here, so I'd not expect changes.

Best regards,

On Thu, Feb 27, 2014 at 5:57 PM, Vladimir Prus <vladimir@xxxxxxxxxxxxxxxx <mailto:vladimir@xxxxxxxxxxxxxxxx>> wrote:


    I'm looking at http://wiki.eclipse.org/__Equinox/p2/Setting_Start___Levels <http://wiki.eclipse.org/Equinox/p2/Setting_Start_Levels> and
    it mentions that default fragment
    is added to all IUs, and in particular it contains this:

        <hostRequirements size='1'>
           <required namespace='org.eclipse.__equinox.p2.eclipse.type' name='bundle' range='0.0.0' multiple='true' greedy='false'/>

        <requires size='1'>
           <required namespace='org.eclipse.__equinox.p2.eclipse.type' name='bundle' range='0.0.0' multiple='true' greedy='false'/>

    What exactly is the role of the 'requires' element? It is rather board requirements already, and then this fragment
    is added to every other IU, so effectively every bundle IU has a requirement that can be satisfied by any other
    bundle IU, and the practical impact of this is rather unclear to me.

    Unrelatedly, looking at http://wiki.eclipse.org/__Equinox/p2/P2_Fragments <http://wiki.eclipse.org/Equinox/p2/P2_Fragments> is seems
    that 'fragments' is used in completely
    different way there? What is the current primary meaning?

    Thanks in advance,

    Vladimir Prus
    CodeSourcery / Mentor Graphics
    http://www.mentor.com/__embedded-software/ <http://www.mentor.com/embedded-software/>
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    p2-dev@xxxxxxxxxxx <mailto:p2-dev@xxxxxxxxxxx>
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-- Krzysztof Daniel https://twitter.com/kda

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Vladimir Prus
CodeSourcery / Mentor Graphics