DSpace Item Level Versioning Support

Introduction

DSpace Item Level Versioning Support is a funded open source activity to bring work done by NESCent and @mire into the DSpace 3.0 Codebase.  Additional partners have signed onto this activity to assure that resources are available to drive Item Versioning Support forward and make it available to the larger DSpace community in the next release.

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Key Stakeholders involved with Item Versioning Support:

• Mark Diggory - @mire
• Holly Miller - MBL
• Diane Rielinger - MBL
• Lisa Raymond - WHOI 
• Ryan Scherle - NESCent / Dryad

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Edit Item and Version Management

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Technical Requirements and Existing Implementation

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The versioning support in Dryad is based on replicating DSpace Item, MetadataValue and Bundle Records, creating an identical version of all Metadata and Bitstream relationships. The new version of the Item "conserves" “conserves” Bitstream Contents by reusing references to the persisted Bitstreams across individual Item Revisions. 

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DSpace Item Versioning will be encapsulated as an Extensible Service that may be reimplemented by the local repository maintainers to produce alternate versioning behaviors and Identifier Schemes. Versioning Services layer on top of IdentifierServices dedicated to Encoding, Resolution, Minting and Registration of Identifiers for specific DSpace Items and Bitstreams.  It is through this highly extensible layering of functionality where local developers can alter the versioning behavior and introduce their own local enhancements.  The DSpace Service Manager, based on the Spring Framework, provides the key leverage for this flexibility.

Versioning Service

The Versioning Service will be responsible for the replication of one or more Items when a new version is requested.  The new version will not yet be preserved in the Repository, it will be preserved when the databases transactional window is completed, thus when errors arise in the versioning process, the database will be properly kept in its original state and the application will alert that an exception has occurred that is in need of correction.

The Versioning Service will rely on a generica generic IdentifierService that is described below for minting and registering any identifiers that are required to track the revision history of the Items.

Dryad Example: Version 1, Version 2 of same document (see versions listed at bottom of page)

Code: Google Code

public interface VersioningService {

    Version createNewVersion(Context c, int itemId);

    Version createNewVersion(Context c, int itemId, String summary);

    void removeVersion(Context c, int versionID);

    void removeVersion(Context c, Item item);

    Version getVersion(Context c, int versionID);

    Version restoreVersion(Context c, int versionID);

    Version restoreVersion(Context c, int versionID, String summary);

    VersionHistory findVersionHistory(Context c, int itemId);

    Version updateVersion(Context c, int itemId, String summary);

    Version getVersion(Context c, Item item);

}

Identifier Service

The Identifier Service maintains an extensible set of IdentifierProvider services that are responsible for two important activities in Identifier management:

1. Resolution: IdentifierService act in a manner similar to the exisitng HandleManager in DSpace, allowing for resolution of DSpace Items from provided identifiers.
2. Minting: Minting is the act of reserving and returning an identifier that may be used with a specific DSpaceObject.
3. Registering: Registering is the act of recording the existence of a minted identifier with an external persistent resolver service, these services may reside ont he local machine (HandleManager) or exist as external services (PURL or DEZID DOI registrations services)

Dryad Example: The same document can be accessed via different identifiers: DOI link (http://dev.datadryad.org/resource/doi:10.5061/dryad.1385.2), Handle link (http://dev.datadryad.org/resource/info:hdl/10255/dryad.36265), default DSpace Link (http://dev.datadryad.org/resource/10255/dryad.36265)

Code: Google Code

Application IdentifierService Interface

public interface IdentifierService {

    void reserve(Context context, Item item) throws AuthorizeException, SQLException, IdentifierException;

    String register(Context context, Item item) throws AuthorizeException, SQLException, IdentifierException;

    DSpaceObject resolve(Context context, String identifier) throws IdentifierNotFoundException, IdentifierNotResolvableException;

    void delete(Context context, Item item) throws AuthorizeException, SQLException, IdentifierException;
}

Backend IdentifierProvider Interface

public abstract class IdentifierProvider {

    protected IdentifierService parentService;

    protected ConfigurationService configurationService;

    @Autowired
    @Required
    public void setConfigurationService(ConfigurationService configurationService) {
        this.configurationService = configurationService;
    }

    public void setParentService(IdentifierService parentService) {
        this.parentService = parentService;
    }

    public abstract boolean supports(String identifier);

    public abstract String register(Context context, DSpaceObject item) throws IdentifierException;

    public abstract String mint(Context context, DSpaceObject dso) throws IdentifierException;

    public abstract DSpaceObject resolve(Context context, String identifier, String... attributes)
         throws IdentifierNotFoundException, IdentifierNotResolvableException;;

    public abstract void delete(Context context, DSpaceObject dso) throws IdentifierException;
}

Example of Spring Configuration for Default HandleProvider Support

http://code.google.com/p/dryad/source/browse/trunk/dryad/dspace/modules/identifier-services/src/main/resources/spring/spring-dspace-core-services.xml

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Support for resolving identifiers via DSpace User Interface

The Resource Path "/resource/..."

Dryad supports a unique identifier resolving service based on Spring WebMVC which allows Identifiers registered within the IdentifierServices to be dereferenced to varied representations of the actual DSpace Items. This resolution can span dspace to alternative webapplications to support various representation formats. The mechanism is extendable in the XMLUI and will be utilized to support dereferencing identifiers via content negotiation to expose alternative format representations of the Item, in Dryad the following are currently implemented.

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