Revision: Configuration Management Resource Definitions

Contents

• OSLC Core properties used by all Configuration Management resources
• Concept resources and version resources
• Configuration Item
• Configuration
• Component
• Configuration context
• Version skew
• Change set
• Creation Factories
• Delegated UIs

OSLC Core properties used by all Configuration Management resources

Concept resources and version resources

A GET on the URI of a concept resource resolves that URI to an appropriate state of (version of) a concept resource for the appropriate configuration context (see later). The returned resource may contain RDF statements about both the version resource and the concept resource; most statements should use the concept resource as the subject, because a version resource reflects the state of (properties of) the concept resource as it appeared at some time. Using the concept resource URI as the subject of RDF statements is more consistent with the handling of non-versioned resources; using the versioned resource URI as the subject of RDF statements requires more client knowledge of versioning.

Since different versions reflecting different states of the concept resource may return conflicting RDF statements about the same subject, it is important for clients handling multiple versions (multiple configurations) to keep track of the relevant versions; this may be done using RDF named graphs.

The dcterms:isVersionOf property relates the version resource itself to its concept resource; this property is mandatory for all versioned resources.

As an example, GET http://example.com/conceptResourceA in one configuration context might return:

    :conceptResourceA-version23
        dcterms:isVersionOf :conceptResourceA .
    :conceptResourceA
        a :someType ;
        dcterms:title "Concept Resource A" ;
        :color "blue" ;
        dcterms:description "Concept resource A as it appears in the state with the URI :conceptResourceA-version23" .

while in a different configuration context it might return:

    :conceptResourceA-version17
        dcterms:isVersionOf :conceptResourceA .
    :conceptResourceA
        a :someType ;
        dcterms:title "Concept Resource A" ;
        :color "red" ;
        dcterms:description "Concept resource A as it appears in the state with the URI :conceptResourceA-version17" .

While the Linked Data Platform indicates that every concept resource should define at least one rdf:type, current practice does not require a type property on the version resource.

To keep track of which version represented which state of the conflicting color statements, use of RDF named graphs is recommended, as shown here using TriG:

:conceptResourceA-version23 = {
    :conceptResourceA-version23
        dcterms:isVersionOf :conceptResourceA .
    :conceptResourceA
        a :someType ;
        dcterms:title "Concept Resource A" ;
        :color "blue" ;
        dcterms:description "Concept resource A as it appears in the state with the URI :conceptResourceA-version23" .
}.
 
:conceptResourceA-version17 = {
    :conceptResourceA-version17
        dcterms:isVersionOf :conceptResourceA .
    :conceptResourceA
        a :someType ;
        dcterms:title "Concept Resource A" ;
        :color "red" ;
        dcterms:description "Concept resource A as it appears in the state with the URI :conceptResourceA-version17" .
}.

Configuration Item

Resources of any type may appear as configuration items - resource that appear as members of configurations or change sets. Configuration items MAY have any of the common properties shown above, and MAY have any other properties. Configuration items that represent versions of a concept resource MUST have the dcterms:isVersionOf property referencing that concept resource. Configuration items that are versioned resources have the following additional properties:

Configuration

A configuration is a Linked Data Platform Container resource with the common properties, plus the following:

Component

A component is a Linked Data Platform Container identifying a set of resources that are configured together as a unit. The granularity of a component varies between providers, but typically it contains the set of resources of some type being used in some project, or a subdivision of such a set. A component has the common properties, plus the following:

A component itself MAY be a versioned resource, indicated by the presence of the dcterms:isVersionOf property referencing the component concept resource.

Configuration context

The initial configuration context is to be established by the user and the system in an appropriate manner - possibly stored in a preference, picked up from an initial resource, selected from a dialog, etc.

While navigating between resources, resources of certain types MAY indicate that a different context is to be used when followings links from that resource. TBD. For example, if a member of the current configuration context is itself a configuration, that sub-configuration MUST be used as the context for resources contained in that sub-configuration. Alternatively, the RELM 1.0 RDF Specification shows use of the vvc:foreignConfiguration predicate to indicate a switch in the configuration context. We need a standard way to express the resource types and predicates to be used for this purpose.

A client may request a specific configuration context in one of four ways. TBD: we need to simplify this. URIs for resources-in-a-configuration-context, whatever their form, should be obtained from providers in some standard manner: clients should never need to construct such URIs themselves - for example, using string manipulation to append a query string.

• When performing a GET on a concept URI, add an X-OSLC-Configuration-Context header, passing the URI of a configuration resource as the value:

    GET /resources/conceptResourceA HTTP/1.1
    X-OSLC-Configuration-Context: http://example.com/configurations/myConfiguration1

• When performing a GET on a concept URI, add a query string oslc_config.context and the encoded configuration URI to the end of the request URI:

    GET /resources/conceptResourceA?oslc_config.context=&3Chttp&3A//example.com/configurations/myConfiguration1&3E HTTP/1.1

• When performing a GET on a configuration URI, add an X-OSLC-Concept-Resource header, passing the URI of a concept resource as the value:

    GET /configurations/myConfiguration1 HTTP/1.1
    X-OSLC-Concept-Resource: http://example.com/resources/conceptResourceA

• When performing a GET on a configuration URI, add a query string oslc_config.concept_resource and the encoded concept resource URI to the end of the request URI:

    GET /configurations/myConfiguration1?oslc_config.concept_resource=&3Chttp&3A//example.com/resources/conceptResourceA&3E HTTP/1.1

Links should be created using the appropriate URI form for the given type of link - a URI for a version resource for links from change sets and most link types from change requests, and a URI for a concept resource for traceability links between versioned resources, or (rarely) a URI for a concept resource plus a configuration context for a link to the current version of the resource in that named context.

Version skew

In large or complex systems, it is often the case that two or more different versions of the same artifact or component are used in different places in that system. This often surfaces at the granularity of components or sub-configurations in larger aggregate or composite configurations, where two different components in turn use two different versions of a shared sub-component.

In situations with version skew, a GET request for a concept resource in the context of the top-level aggregate or composite configuration is ambiguous, and MUST fail with a 409 Conflict HTTP status code. The client may reissue the request with a more specific configuration context. Providers MAY allow other methods for disambiguating requests in the presence of version skew, such as some form of path or location information.

Change set

A change set is a resource with any of the above-listed standard properties, plus the following:

Creation Factories

A configuration provider MUST provide a creation factory for new configurations. A configuration provider MAY provide a creation factory for configuration items, but this specification does not determine the semantics of or required properties for configuration item factories.

Delegated UIs

A configuration provider SHOULD delegated user interface dialogs for creation and selection of configurations. A configuration provider MAY also provide delegated dialogs for creation and selection of configuration items.