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  • Project Dependency Trees schema

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Excerpt

The Project Dependency Trees artifact defines all the side artifacts of a project as well as each artifacts tree of dependencies. This can be used by consumers to decide what the consumers effective tree of dependencies is as well as allowing consumers to perform intelligent substitutions in the tree. By providing the entire tree we can reduce the number of requests a consumer needs to make in order to resolve all the artifacts the consumer requires.

There are a number of issues with the current Project Object Model used by Maven:

  • We do not have a good way to evolve the model or even change the model version
  • We do not have a good way to model the differences in dependencies for the individual artifacts that get deployed as part of the project
  • We do not have a good way to augment the information if we are deploying artifacts from the project non-atomically
  • The model is weakly specified with regards to conflict resolution and exposes Java native assumptions about conflict resolution.
  • The model does not allow for reproducible builds while simultaneously allowing range specification for dependencies
  • The model exposes build time information that is irrelevant to consumers

The aim of the Project Dependency Trees model is to resolve these issues.

Model evolution

One of the top level elements of the Maven POM is the modelVersion element that specifies the model version for the POM. To date there have been two model versions 3.0.0 and 4.0.0. In both cases, a critical issue for changing the model version is that older clients cannot parse the newer model. This required the forking of Central (which is why central is repo.maven.org/maven2 because 4.0.0 was introduced with Maven 2 and Maven 1 clients could not parse the new model version)

Obviously, newer clients can always be written to parse older model versions, but given that Central is now a resource used by multiple build tools, not all of which run on the JVM or are maintained by the Apache Maven community, we need to ensure that any solution does not break the ability of other clients to consume the artifacts published to central.

NOTE: while we need to ensure that artifacts can be consumed by both older clients, we do not have to ensure that the older clients get the exactly correct dependency tree. Rather we should make the best effort possible to give older clients as good a dependency tree as we can give them.

Model evolution will be handled in two ways, based on the type of client:

  • Legacy clients are clients that are not aware of the Project Dependency Trees model
  • Modern clients are clients that are aware of the Project Dependency Trees model, but need not necessarily be aware of the latest modelVersions deployed by the newest version of Maven.

Legacy clients

Legacy clients cannot be aware of the Project Dependency Trees model. For this reason, any project that deploys a Project Dependency Trees model will also deploy a modelVersion 4.0.0 POM which is the best-effort translation of the Project Dependency Trees model for the primary artifact of the project.

Modern clients

As part of the process of evolving a Project Dependency Trees schema, each new version of the model will be accompanied by an XSLT transformation(s) that will be published into Central at a defined set of coordinates. This will allow a modern client to convert a schema - that is newer than the highest modelVersion it was built against - into the newest modelVersion that it supports. In general the XSLT transformation will essentially strip out elements that are not understood by older clients, though it is possible that more adventurous transformations may be included.

The rationale for choosing XSLT as the transformation... and consequently forcing the Project Dependency Trees model to be expressed in XML is that XSLT is currently the only cross-platform transformation engine available across the JVM, Ruby, .NET, C/C++ native code and JavaScript runtimes.

TODO write the content and formalise the following example into a schema:

 

<project

...

modelVersion="..."

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="...">
 

...

 

...

<information>
 

...

 

...

 

...

 

...

<!--

...

container

...

for

...

descriptive

...

information

...

-->
 

...

 

...

 

...

 

...

[<name>...</name>]
 

...

 

...

 

...

 

...

[<description>...</description>]
 

...

 

...

 

...

 

...

...
 

...

 

...

</information>

...

<license

...

spdxId="..."/>

...

<license

...

spdxId="..."/>

...

...

...

<license

...

spdxId="..."/>
 

...

 

...

<artifacts

...

[platformId="..."]>
 

...

 

...

 

...

 

...

<artifact

...

type="..."

...

[classifier="..."]>
 

...

 

...

 

...

 

...

 

...

 

...

<information>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

<!--

...

optional

...

element

...

if

...

need

...

to

...

override

...

root

...

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...

information

...

for

...

specific

...

artifacts

...

-->
 

...

 

...

 

...

 

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...

 

...

</information>
 

...

 

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<!-- 
 

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...

components

...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

requiring

...

more

...

general

...

validation
 

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...

 

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...

e.g.

...

for

...

Java

...

9+

...

the

...

ids

...

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...

be

...

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...

module

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ids

...

if

...

we

...

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...

to

...

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...

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...

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...

module

...

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...

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...

unique

...

in

...

the
 

...

 

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effective

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tree.
 

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set

...

of

...

licenses

...

from

...

those

...

defined

...

at

...

the

...

project

...

level,

...

we

...

define

...

the

...

licenses

...

of

...

this

...

artifact

...

here.

...

Otherwise

...

we

...

defer

...

to

...

the

...

licenses

...

defined

...

at

...

the

...

top

...

level

...

of

...

the

...

project.
 

...

 

...

 

...

 

...

 

...

 

...

 

...

licensing

...

is

...

a

...

top

...

level

...

concern,

...

and

...

legitimately

...

can

...

vary

...

per

...

artifact.

...

Let's

...

not

...

solve

...

license

...

compatibility, 
 

...

 

...

 

...

 

...

 

...

 

...

 

...

rather

...

leverage https://spdx.org/
 

...

 

...

 

...

 

...

 

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-->
 

...

 

...

 

...

 

...

 

...

 

...

<license

...

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...

spdx:id="..."/>
 

...

 

...

 

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...

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...

 

...

 

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<license

...

spdx:id="..."/>
 

...

 

...

 

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...

<!--
 

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provides

...

is

...

a

...

marker

...

that

...

we

...

have

...

duplication

...

of

...

content.

...

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...

could

...

be

...

because

...

we

...

are

...

much

...

like

...

the

...

many

...

servlet-api

...

jar
 

...

 

...

 

...

 

...

 

...

 

...

 

...

files

...

where

...

there

...

are

...

many

...

GAV's

...

of

...

the

...

same

...

javax.servlet:servlet-api:3.0

...

thus

...

we

...

could

...

have

...

the

...

case

...

where
 
 

...

 

...

 

...

 

...

 

...

 

...

 

...

org.jboss.spec.javax.servlet:jboss-servlet-api_3.0_spec:jar:1.0.2.Final

...

PROVIDES

...

javax.servlet:servlet-api:3.0
 

...

 

...

 

...

 

...

 

...

 

...

 

...

org.jboss.spec.javax.servlet:jboss-servlet-api_3.0_spec:jar:1.0.1.Final

...

PROVIDES

...

javax.servlet:servlet-api:3.0
 

...

 

...

 

...

 

...

 

...

 

...

 

...

org.jboss.spec.javax.servlet:jboss-servlet-api_3.0_spec:jar:1.0.0.Final

...

PROVIDES

...

javax.servlet:servlet-api:3.0
 

...

 

...

 

...

 

...

 

...

 

...

 

...

org.mortbay.jetty:servlet-api-3.0:jar:7.0.0pre2

...

PROVIDES

...

javax.servlet:servlet-api:3.0
 
 

...

 

...

 

...

 

...

 

...

 

...

 

...

similarly
 
 

...

 

...

 

...

 

...

 

...

 

...

 

...

org.slf4j:log4j-over-slf4j:jar:1.7.21

...

PROVIDES

...

log4j:log4j:[1.0,2)
 
 

...

 

...

 

...

 

...

 

...

 

...

 

...

The

...

consumer

...

of

...

the

...

tree

...

can

...

then

...

decide

...

if/when/how

...

to

...

collapse

...

redundant

...

nodes

...

as

...

they

...

see

...

fit.
 
 

...

 

...

 

...

 

...

 

...

 

...

 

...

TODO:

...

decide

...

optionality

...

of

...

version

...

and

...

range

...

attributes
 

...

 

...

 

...

 

...

 

...

 

...

-->
 

...

 

...

 

...

 

...

 

...

 

...

<provides

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

[range="..."]

...

type="..."

...

[classifier="..."]>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

<!--

...

no

...

elements

...

here

...

as

...

we

...

have

...

"rebundled"

...

hence

...

implicitly

...

promoted

...

up

...

one

...

level-->
 

...

 

...

 

...

 

...

 

...

 

...

</provides>
 

...

 

...

 

...

 

...

 

...

 

...

<provides

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

[range="..."]

...

type="..."

...

[classifier="..."]/>
 

...

 

...

 

...

 

...

 

...

 

...

...
 

...

 

...

 

...

 

...

 

...

 

...

<provides

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

[range="..."]

...

type="..."

...

[classifier="..."]/>
 

...

 

...

 

...

 

...

 

...

 

...

<!--
 

...

 

...

 

...

 

...

 

...

 

...

 

...

requires

...

are

...

the

...

mandatory

...

dependencies.

...

This

...

is

...

effectively

...

a

...

recursive

...

artifact

...

where

...

the

...

GAV

...

is

...

not

...

inherited

...

and
 

...

 

...

 

...

 

...

 

...

 

...

 

...

where

...

we

...

have

...

discarded

...

the

...

information

...

section.

...

If

...

you

...

want

...

those

...

details,

...

fetch

...

that

...

project's

...

dependencies

...

trees.
 

...

 

...

 

...

 

...

 

...

 

...

-->
 

...

 

...

 

...

 

...

 

...

 

...

<requires

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

range="..."

...

type="..."

...

[classifier="..."]>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

<component

...

id="..."/>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

<license

...

spdx:id="..."/>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

<provides

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

[range="..."]

...

type="..."

...

[classifier="..."]/>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

<requires

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

range="..."

...

type="..."

...

[classifier="..."]>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

...
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

</requires>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

<supports

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

[range="..."]

...

type="..."

...

[classifier="..."]/>
 

...

 

...

 

...

 

...

 

...

 

...

</requires>
 

...

 

...

 

...

 

...

 

...

 

...

<requires

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

range="..."

...

type="..."

...

[classifier="..."]>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

...
 

...

 

...

 

...

 

...

 

...

 

...

</requires>
 

...

 

...

 

...

 

...

 

...

 

...

...
 

...

 

...

 

...

 

...

 

...

 

...

<requires

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

range="..."

...

type="..."

...

[classifier="..."]>
 

...

 

...

 

...

 

...

 

...

 

...

 

...

 

...

...
 

...

 

...

 

...

 

...

 

...

 

...

</requires>
 

...

 

...

 

...

 

...

 

...

 

...

<!--
 

...

 

...

 

...

 

...

 

...

 

...

 

...

supports

...

are

...

the

...

optional

...

dependencies.

...

We

...

list

...

them

...

here

...

to

...

aid

...

in

...

conflict

...

resolution.

...

We

...

do

...

not

...

include

...

a

...

nested

...

tree
 

...

 

...

 

...

 

...

 

...

 

...

 

...

as

...

a

...

consumer

...

would

...

only

...

pull

...

them

...

in

...

if

...

the

...

consumer

...

already

...

has

...

its

...

own

...

a

...

requires

...

for

...

them,

...

so

...

we

...

really

...

only
 

...

 

...

 

...

 

...

 

...

 

...

 

...

need

...

to

...

validate

...

the

...

range. 
 
 

...

 

...

 

...

 

...

 

...

 

...

 

...

TODO:

...

decide

...

optionality

...

of

...

range

...

attribute
 

...

 

...

 

...

 

...

 

...

 

...

 

...

TODO:

...

decide

...

if

...

we

...

want

...

a

...

version

...

attribute 
 

...

 

...

 

...

 

...

 

...

 

...

-->
 

...

 

...

 

...

 

...

 

...

 

...

<supports

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

[range="..."]

...

type="..."

...

[classifier="..."]/>
 

...

 

...

 

...

 

...

 

...

 

...

<supports

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

[range="..."]

...

type="..."

...

[classifier="..."]/>
 

...

 

...

 

...

 

...

 

...

 

...

<supports

...

groupId="..."

...

artifactId="..."

...

[platformId="..."]

...

version="..."

...

[range="..."]

...

type="..."

...

[classifier="..."]/>
 

...

 

...

 

...

 

...

</artifact>
 

...

 

...

 

...

 

...

<artifact

...

...>
 

...

 

...

 

...

 

...

 

...

 

...

...
 

...

 

...

 

...

 

...

</artifact>
 

...

 

...

 

...

 

...

...
 

...

 

...

 

...

 

...

<artifact

...

...>
 

...

 

...

 

...

 

...

 

...

 

...

...
 

...

 

...

 

...

 

...

</artifact>
 

...

 

...

</artifacts>

...

<!--

...

if

...

the

...

project

...

does

...

not

...

specify

...

a

...

platformId

...

then

...

we

...

can

...

include

...

additional

...

platform

...

details

...

that

...

were

...

part

...

of

...

the

...

atomic

...

deployment

...

-->

...

<artifacts

...

platformId="...">

...

...

...

</artifacts>

...

...

...

<artifacts

...

platformId="...">

...

...

...

</artifacts>
</project>

 

Schema

Here is a draft XML schema:

 

<xs:schema

...

attributeFormDefault="unqualified"

...

elementFormDefault="qualified"

...

xmlns:xs="http://www.w3.org/2001/XMLSchema"

...

>

...

<xsd:simpleType

...

name=”coordinate”>

...

<xsd:restriction

...

base=”xsd:string”>

...

<!--

...

TODO

...

add

...

pattern

...

for

...

groupId/artifactId/platformId/version/type/classifier

...

valid

...

values

...

-->

...

</xsd:restriction>

...

</xsd:simpleType>

...

<xs:element

...

name="project">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;project&gt;</code>

...

element

...

is

...

the

...

root

...

of

...

the

...

project

...

dependency

...

trees.

...

</xs:documentation>

...

</xs:annotation>

...

<xs:complexType>

...

<xs:attribute

...

name="modelVersion"

...

type="xs:string"/>

...

<xs:attribute

...

name="groupId"

...

type="coordinate"/>

...

<xs:attribute

...

name="artifactId"

...

type="coordinate"/>

...

<xs:attribute

...

name="version"

...

type="coordinate"/>

...

<xs:attribute

...

name="platformId"

...

type="coordinate"

...

use="optional"/>

...

<xs:all>

...

<xs:element

...

ref="information"

...

minOccurs="0"

...

maxOccurs="1"/>

...

<xs:element

...

ref="license"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="artifacts"

...

minOccurs="1"

...

maxOccurs="unbounded"/>

...

</xs:all>

...

</xs:complexType>

...

</xs:element>

...

<xs:element

...

name="information">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;information&gt;</code>

...

element

...

is

...

a

...

container

...

for

...


...

descriptive

...

information

...

about

...

either

...

all

...

the

...

artifacts

...

in

...

a

...

project

...

or

...


...

a

...

specific

...

artifact.</xs:documentation>

...

</xs:annotation>

...

<xs:complexType>

...

<xs:all>

...

<xs:element

...

name="name"

...

type="xs:string"

...

maxOccurs="1"/>

...

<xs:element

...

name="description"

...

type="xs:string"

...

maxOccurs="1"/>

...

<!--

...

TODO

...

add

...

additional

...

elements

...

-->

...

</xs:all>

...

</xs:complexType>

...

</xs:element>

...

<xs:element

...

name="license"

...

xmlns:spdx="http://spdx.org/rdf/terms#">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;license&gt;</code>

...

element

...

defines

...

one

...

of

...

the

...

licenses

...

under

...

which

...

the

...

artifacts

...

are

...

made

...

available.

...

Where

...

a

...

license

...

is

...


...

attached

...

to

...

the

...

<code>&lt;project&gt;</code>

...

element

...

this

...

defines

...

the

...


...

default

...

licenses

...

for

...

all

...

artifacts

...

in

...

the

...

project.

...

Where

...

a

...

license

...

is

...


...

attached

...

to

...

an

...

<code>&lt;artifact&gt;</code>

...

element

...

this

...

signifies

...


...

that

...

the

...

specific

...

artifact

...

is

...

covered

...

by

...

the

...


...

<code>&lt;license&gt;</code>

...

elements

...

defined

...

within

...

that

...


...

<code>&lt;artifact&gt;</code>

...

element.

...

Licenses

...

are

...

identified

...

using

...


...

the

...

<a

...

href="http://spdx.org">SPDX</a>

...

identifiers</xs:documentation>

...

</xs:annotation>

...

<xs:complexType>

...

<xs:attribute

...

name="spdxId"

...

type="xs:string"/>

...

</xs:complexType>

...

</xs:element>

...

<xs:element

...

name="artifacts">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;artifacts&gt;</code>

...

element

...

is

...

a

...

container

...

for

...


...

details

...

of

...

artifacts.

...

When

...

the

...

<code>&lt;artifacts&gt;</code>

...

attribute

...

is

...

missing,

...

then

...

the

...

artifacts

...

listed

...

are

...

not

...

platform

...

specific.

...

The

...

<code>&lt;artifacts&gt;</code>

...

must

...

be

...

unique

...

with

...

respect

...

to

...

their

...

<code>&lt;platformId&gt;</code>,

...

i.e.

...

it

...

cannot

...

be

...

repeated.

...

If

...

the

...

<code>&lt;project&gt;</code>

...

element

...

has

...

a

...


...

<code>&lt;platformId&gt;</code>

...

then

...

there

...

must

...

be

...

only

...

one

...

<code>&lt;artifacts&gt;</code>

...

element

...

and

...

it

...

must

...

have

...

the

...

matching

...

<code>&lt;platformId&gt;</code>.

...

</xs:documentation>

...

</xs:annotation>

...

<xs:complexType>

...

<xs:attribute

...

name="platformId"

...

type="coordinate"

...

use="optional"/>

...

<xs:sequence>

...

<xs:element

...

ref="artifact"

...

minOccurs="1"

...

maxOccurs="unbounded"/>

...

</xs:sequence>

...

</xs:complexType>

...

</xs:element>

...

<xs:element

...

name="artifact">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;artifact&gt;</code>

...

element

...

represents

...

an

...

artifact

...

associated

...

with

...

the

...

project.

...

</xs:documentation>

...

</xs:annotation>

...

<xs:complexType>

...

<xs:attribute

...

name="type"

...

type="coordinate"/>

...

<xs:attribute

...

name="classifier"

...

type="coordinate"

...

use="optional"/>

...

<xs:all>

...

<xs:element

...

ref="information"

...

minOccurs="0"

...

maxOccurs="1"/>

...

<xs:element

...

ref="license"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="component"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="provides"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="requires"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="supports"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

</xs:all>

...

</xs:complexType>

...

</xs:element>

...

<xs:element

...

name="component">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;component&gt;</code>

...

element

...

represents

...

a

...

type

...

specific

...

component

...

that

...

is

...

present

...

within

...

the

...

artifact.

...

For

...

example

...

a

...

"jar"

...

artifact

...

might

...

list

...

the

...

Java

...

9+

...

modules

...

that

...

are

...

included

...

within

...

the

...

"jar".

...

Other

...

file

...

types

...

can

...

use

...

the

...

component

...

according

...

to

...

the

...

conventions

...

of

...

that

...

file

...

type.

...

The

...

component

...

information

...

is

...

intended

...

to

...

assist

...

build

...

time

...

tools

...

in

...

conflict

...

detection

...

when

...

resolving

...

the

...

composite

...

dependency

...

tree

...

according

...

to

...

the

...

build

...

tools

...

dependency

...

resolution

...

strategy.

...

</xs:documentation>

...

</xs:annotation>

...

<xs:complexType>

...

<xs:attribute

...

name="id"

...

type="xs:string"/>

...

</xs:complexType>

...

</xs:element>

...

<xs:element

...

name="provides">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;provides&gt;</code>

...

element

...

represents

...

a

...

semantic

...

equivalence

...

with

...

another

...

artifact.

...

There

...

are

...

several

...

ways

...

the

...

element

...

can

...

be

...

used.

...

<nl>

...

<li>

...

When

...

an

...

artifact

...

directly

...

includes

...

the

...

same

...

content

...

as

...

another

...


...

project's

...

artifacts,

...

for

...

example

...

there

...

are

...

some

...

"jar"

...

files

...

that

...


...

will

...

embed

...

other

...

artifacts

...

to

...

produce

...

a

...

so-called

...

"uber-jar".

...

</li>

...

<li>

...

When

...

an

...

artifact

...

re-implements

...

the

...

API

...

of

...

another

...

project's

...


...

artifact.

...

For

...

example:

...

log4j-over-slf4j

...

reimplements

...

the

...

log4j

...

API.

...

</li>

...


...

<li>

...

When

...

a

...

set

...

of

...

projects

...

are

...

co-operating

...

to

...

provide

...

multiple

...

implementations

...

of

...

a

...

"virtual"

...

project

...

artifact.

...

For

...

example:

...

slf4j-log4j,

...

slf4j-jul,

...

and

...

logback

...

could

...

all

...

be

...

considered

...

as

...

providing

...

a

...

slf4j-impl

...

virtual

...

project

...

artifact.

...

There

...

would

...

be

...

no

...

actual

...

project

...

at

...

the

...

slf4j-impl

...

coordinates,

...

but

...

slf4j-api

...

could

...

declare

...

a

...

requirement

...

on

...

the

...

"virtual"

...

project

...

artifact

...

in

...

order

...

to

...

ensure

...

that

...

an

...

implementation

...

is

...

available

...

to

...

consumers

...

of

...

the

...

API

...

</nl>

...

</xs:documentation>

...

</xs:annotation>

...

<xs:complexType>

...

<xs:attribute

...

name="groupId"

...

type="coordinate"/>

...

<xs:attribute

...

name="artifactId"

...

type="coordinate"/>

...

<xs:attribute

...

name="platformId"

...

type="coordinate"

...

use="optional"/>

...

<xs:attribute

...

name="version"

...

type="coordinate"/>

...

<xs:attribute

...

name="range"

...

type="xs:string"/>

...

<xs:attribute

...

name="type"

...

type="coordinate"/>

...

<xs:attribute

...

name="classifier"

...

type="coordinate"

...

use="optional"/>

...

</xs:complexType>

...

</xs:element>

...

<xs:element

...

name="requires">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;requires&gt;</code>

...

element

...

represents

...

a

...

hard

...

dependency

...

on

...

another

...

project's

...

artifact.

...

If

...

the

...

<code>&lt;version&gt;</code>

...

attribute

...

is

...

missing

...

then

...

this

...

indicates

...

that

...

the

...

dependency

...

is

...

a

...

virtual

...

dependency,

...

and

...

there

...

must

...

be

...

no

...

child

...

elements.

...

The

...

<code>&lt;modelVersion&gt;</code>

...

attribute

...

must

...

only

...

be

...

present

...

if

...

the

...

dependent

...

project's

...

<code>&lt;modelVersion&gt;</code>

...

is

...

newer

...

than

...

the

...

<code>&lt;modelVersion&gt;</code>

...

specified

...

on

...

the

...

root

...


...

<code>&lt;project&gt;</code>

...

element.

...

The

...

presence

...

of

...

this

...

element

...

indicates

...

that

...

the

...

child

...

information

...

was

...

the

...

result

...

of

...

an

...

XSLT

...

transformation

...

of

...

a

...

newer

...

<code>&lt;modelVersion&gt;</code>

...

and

...

indicates

...

that

...

a

...

build

...

tool

...

understanding

...

the

...

newer

...


...

<code>&lt;modelVersion&gt;</code>

...

may

...

want

...

to

...

fetch

...

the

...

dependencies

...

tree

...

and

...

process

...

it

...

directly

...

in

...

order

...

to

...

obtain

...

the

...

most

...

correct

...

model

...

of

...

the

...

dependency.

...

</xs:documentation>

...

</xs:annotation>

...

<xs:complexType>

...

<xs:attribute

...

name="groupId"

...

type="coordinate"/>

...

<xs:attribute

...

name="artifactId"

...

type="coordinate"/>

...

<xs:attribute

...

name="platformId"

...

type="coordinate"

...

use="optional"/>

...

<xs:attribute

...

name="version"

...

type="coordinate"

...

use="optional"/>

...

<xs:attribute

...

name="range"

...

type="xs:string"/>

...

<xs:attribute

...

name="type"

...

type="coordinate"/>

...

<xs:attribute

...

name="classifier"

...

type="coordinate"

...

use="optional"/>

...

<xs:attribute

...

name="modelVersion"

...

type="xs:string"

...

use="optional"/>

...

<xs:all>

...

<xs:element

...

ref="license"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="component"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="provides"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="requires"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

<xs:element

...

ref="supports"

...

minOccurs="0"

...

maxOccurs="unbounded"/>

...

</xs:all>

...

</xs:complexType>

...

</xs:element>

...

<xs:element

...

name="supports">

...

<xs:annotation>

...

<xs:documentation

...

source="version">5.0.0+</xs:documentation>

...

<xs:documentation

...

source="description">

...

The

...

<code>&lt;supports&gt;</code>

...

element

...

represents

...

a

...

soft

...

dependency

...

on

...

another

...