Equinox p2 Metadata Authoring

This page describes the design of the proposed p2 meta data authoring project.

Work in Progress - not yet meaningfull to comment

Metadata authoring proposal

The problems this project should solve:

• Many types are automatically "adapted" to installable units (e.g. features and plugins), but there is no direct authoring available.
• Existing "adapted" installable units may have meta data that needs to be modified/augmented in order for the unit to be useful - there is a mechanism available to provide advice to the resolution mechanism, but authoring of such advice is not.

I think the work consists of:

• An XML definition for "authored installable unit" (most likely the <unit> format in the local meta data repository). It should be possible to create such an "iu" file with any name without requirements that it is in some special project or folder.
• An XML definition for "advice to adapted installable unit" (as I am not sure what is needed here, a separate definition is perhaps needed).
• An editor for Installable Unit
• Ad editor for Installable Unit advice (is perhaps the same editor).
• A way to test the installable unit (resolution, install-ability)
• A way to export/publish installable units

Files and Formats

The format of the "IU" file

It seems obvious to reuse the xml format from the local meta data repository as it already describes an installable unit.

<?xml version='1.0' encoding='UTF-8'?>
<?InstallableUnit class='org.eclipse.equinox.internal.p2.metadata.InstallableUnit' version='1.0.0'?>
<installable version="1.0.0">
     <unit>
           <!-- like local metadata repository for 'unit' element -->
     </unit>
</installable>

In order to make it easier to reuse the parser/writer for the local metadata repository, a new root element "<installable>" is used to wrap a single "<unit>" element. This also opens up the possibility to include other elements (than unit) if required.

Naming convention

To make it easy to detect the "IU" files an ".iu" extension should be required.

Writer/Parser design

It was possible to crete a prototype that read and writes this format by reusing the metadata repository XMLReader and XMLWriter. It is however a bit unclear if the intention is to allow the InstallableUnit to be used by an editor, or if these classes should be considered internal/private.

IU Attributes and Editing

In this section the installable unit attributes editing concerns are discussed.

Namespace

The namespace is the naming scope of the installable unit's name. From what has been understood by looking at some installable, these are examples of namespaces:

• org.eclipse.equinox.p2.iu
• org.eclipse.equinox.p2.eclipse.type
• osgi.bundle
• java.package
• org.eclipse.equinox.p2.localization

Questions?

• Should the user be allowed to type anything in the namespace field?
• If not allowed to type anything - where are the valid namespaces found?
• Can the set of namespaces be extended?
• Does namespace have a valid format (looks like it follows package name format)?
• Can namespace be left empty?

ID

Questions

• Is ID editable or is it calculated?
• How is ID used? It seems like IU's use namespace/name to match required elements - is ID only a reference to an IU in a metadata repository? If so, how should it be used when editing?

Name

Questions

• What is the valid format of a name?
• Is format determined by p2 for all namespaces, or can name format vary between different namespaces?
• If it can vary, how is the namespace/name validation extended to new namespaces?

Prototype Implementation

In the prototype, the assumption is that the name should follow structured java naming - i.e. a pattern that:

• name can consist of multiple parts where parts are separated by a "."
• each part must be at least one char long
• each part must begin with a-zA-Z_$
• subsequent chars in a part can be a-zA-Z0-9_$

Version

Version is an OSGi version and is validated as one. Version is required.

Provider

Optional string value. No validation.