DSpace REST API - Bojan Suzic

Integration, testing, documentation and further development of DSpace REST services for 1.x and 2.0 versions. - Bojan Suzic

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Details

Project Title:	DSpace REST API
Student:	Bojan Suzic, University of Technology Graz
Mentors:	Aaron Zeckoski, Mark Diggory
Contacting author:	bojan AT student . tugraz DOT at - using subject line DSpace
SCM Location for Project:	http://scm.dspace.org/svn/repo/modules/rest

Project description

The REST approach promotes simplification and decoupling of software architecture, enabling further scalability, portability, granularity and simplified interaction of software systems and components.
The aim of this project is to provide DSpace with REST capable API and underlying component, which will enable developers and end-users to exploit the advantages of such approach.

Some of uses this module is intended to provide could be, for instance:

interaction between DSpace systems and/or other repositories
automation of different activities, e.g. submission of packages
integrating repositories in process workflows of other applications or systems
interaction with many kinds of systems or web applications, such as CMS, LMS, LCMS, VLS, AMS etc
providing of other approaches to UI, such as client based/run UI
crawling of repositories, exposing information in structural way

This project is continuation of last year's activities, supported by Google as part of GSoC 2009. In the first stage the basic support for REST for DSpace is provided, exposing many parts of DSpace functionality to the clients.

In this year's GSoC the following activities should be primarily addressed:

integration of existing code in the system
alignment of REST API with currently available DSpace features/functionality, e.g. adding of new features
extending of existing code, in order to provide better handling of management and injection functions
providing more detailed documentation and examples for end users
testing activities, e.g. cooperation/coordination with other GSoC 10 project Unit testing
promotion of DSpace REST interaction (by taking part in integration with other systems)

Detailed activities

In the following sections main activities are elaborated in detail.

REST API Methods

Changes in comparison to existing support are marked with red color. Please note that changes may appear as:

introduction of new method
extending of existing method, by implementing new functionality (e.g. GET/PUT/DELETE)
extending of existing method, by changing its parameters, output etc

Naming convention for endpoints
DSpace 1.x and 2.x are treating the resources on different way. 2.x is more generalized, suggesting the use of RDF-like interrelation notations.

Repository browsing

Earlier Implementation Description - GSoC09

C	Verb	URL	Description	Mandatory parameters	Optional parameters	Sorting fields	Response Data	Formats	Response codes
	`GET`	`/communities`	Returns a list of all communities on the system or return just top level communities.	-	`topLevelOnly=true` `idOnly=false`	`id` name `countitems`	The list of communities containing respective fields . Response code details: `204` - if there are no communities on the system	`json` `xml`	200, 204, 400, 500
•	`GET`	`/communities/{id`	Return detailed information about `id` community.	`id`	`idOnly=false`	-	Fields describing community.	`json` `xml`	200, 400, 404, 500
•	`GET`	`/communities/{id}/{element`}	Return a particular data field found in the community `id` Fields supported (for `element`): `id` - entity identifier, internal to the system `name` - entity name `countItems` - number of items under community `handle` - handle of the community (unique persistent resource identifier) `type` - entity type (object type in the system) `collections` - collections contained in the community, ordered by id `canedit` - states user persmission on the community (editing) `anchestor` - anchestors of the community `children` - subcommunities, ordered by id `administrators` - group administrators, ordered by id `recent` - recent items in the community `shortDescription` - short description `copyrightText` - copyright text `sidebarText` - sidebar text `introductoryText` - introductory text	`id`	`idOnly=false` `immediateOnly=true`	`id` `name` `countitems`	Respective field info	`json` `xml`	200, 204, 400, 500
•	`GET`	`/communities/{id}/logo`	Return a community logo	`id`	-	-	Contains community logo (bitstream)	`binary`	200, 400
•	`GET`	`/collections`	Return a list of all collections in the system.	-	`idOnly=false` `isAuthorized=false`	`id` `name` `countitems`	The list of the collections containing respective fields. Response code details: `204` - if there are no communities on the system	`json` `xml`	200, 204, 400, 500
•	`GET`	`/collections/{id`}	Return detailed information about `id` collection	`id`	`idOnly=false`	`id` `name` `countitems`	Fields of the collection entity.	`json` `xml`	200, 204, 400, 500
•	`GET`	`/collections/{id}/{element`}	Return a particular data field found in the collection `id`. Fields supported (for `element`): `id` - entity identifier, internal to the system `name` - collection name `licence` - collection licence `items` - items contained in collection `handle` - handle of the collection (unique persistent resource identifier) `canedit` - states user permission on the collection (edit) `communities` - communities collection is a part of `countItems` - number of the items in the collection `type` - entity type (object type in the system) `shortDescription` - short description of the collection `introText` - introductory text for the collection `copyrightText` - copyright text for the collection `sidebarText` - sidebar text for the collection `provenance` - provenance	`id`	`idOnly=false` `immediateOnly=true`	`id` `name` `countitems`	Respective field info	`json` `xml`	200, 204, 400, 500
	`GET`	`/items`	Return a list of the items in the system	-	-	-	The list of the items containing related fields . Response code details: `204` - if there are no communities on the system
	`GET`	`/items/{id`}	Return detailed information about an item.	`id`	-	`id` `name` `lastmodified` `submitter`	Fields of the item entity.	`json` `xml`	200, 204, 400, 500
	`GET`	`/items/{id}/{element`}	Return a particular data field fould in the item `id` Fields supported (for `element`): `metadata` - item metadata `submitter` - submitter group `isArchived` - archival status of the item `isWithdrawn` - states if the item is withdrawn `owningCollection` - owning collection of the item `lastModified` - last modified time `collections` - collections the item appears in `communities` - communities the item appears is `name` - name of the item `bitstreams` - bitstreams related to the item `handle` - item handle (unique identified) `canedit` - states can user edit the item `id` - item id `type` - element type `bundles` - bundles related to the item	`id`, `element`	-	-	Respective field info	`json` `xml`	200, 204, 400, 500
	`GET`	`/bitstream/{id`}	Return bitstream object - usually the library item file.	`id`	-	-	`id` - id of bitstream `name` - name of the bitstream `bundles` - bundles the related bitstream appears in `checksum` - checksum of bitstream `checksumAlgorithm` - checksum algorithm used `description` - bitstream description `formatDescription` - format description of bitstream `handle` - bitstream handle `mimeType` - mime type of bitstream `sequenceId` - sequence id `size` - bitstream size in bytes `source` - bitstream source, local `storeNumber` - store number `type` - object type `userFormatDescription` - description of user format	`json`, `xml`	200, 400, 401, 403, 404, 500
	`GET`	`/bitstream/{id}/receive`	Return bitstream	`id`	-	-	Return bitstream	`binary`	200, 400, 401, 403, 404, 500

Note: modifier idOnly is referred only to first layer of the results. For all other layers (e.g. nested results) only ids are returned in some cases, due to possible loops. Example: for community containing collections, on second level the response contains only ids for some elements where multiple loops may be created (community->has_collection->has_community....). Other data is modified according to idOnly flag.

Optional parameters

Parameter	Description
`topLevelOnly`	returns only top level communities
`idOnly`	if true return only the identifiers for the record
`immediateOnly`	return only direct parent community
`isAuthorized`	return only collections user has permission to work on
`inArchive`	return archived items for respective collection

Sorting fields:

Parameter	Description	Ordering supported
`id`	sort results by entity id	`asc` \| `ascending` `desc` \| `descending`
`name`	sort results by entity name	`asc` \| `ascending` `desc` \| `descending`
`countitems`	sort results by number of items contained	`asc` \| `ascending` `desc` \| `descending`
`lastmodified`	sort results by date of last item modification	`asc` \| `ascending` `desc` \| `descending`
`submitterName`	sort results by submitter name	`asc` \| `ascending` `desc` \| `descending`
`submitterId`	sort results by submitter id	`asc` \| `ascending` `desc` \| `descending`

Controlling results

Parameter	Description	Default	Example
`_start`	position of the first entity to return	0 (first)	`_start=5` to list 6th item and onwards
`_page`	page of data to display	0 (first)	`_page=2`, to display second page with query results
`_perpage`	number of results to show on each page	0 (all)	`_perpage=10` to display 10 results per page
`_limit`	maximum number of entities to return	0 (all)	`_limit=50`
`_sort`		the sort order to return entities in should be comma separated list of field names suffix determines ordering suffixes: `_asc`, `_ascending`, `_desc`, `_descending` ascending default	`sort=name` `_sort=name,email_desc,lastname_desc`

Response codes

Code	Description
200	OK
201	Created
204	No content
400	Bad request
401	Unauthorized
403	Forbidden
404	Not found
405	Method not allowed
500	Internal server error
503	Service unavailable

Authentication/Authorization

Currently only standard authentication is supported. The authentication data is provided in the request or header body.

Example:

/rest/communities.json?user=user@email.com&pass=userpassword

The same elements user and pass are used for header based authentication.

Authorization is done on underlying api level; in the case of error the proper message and error code are returned to the user.

Repository manipulation

C	Verb	URL	Description	Mandatory parameters	Optional parameters	Response Data	Formats	Response codes
•	`POST`	`/communities`	Action to be done under community `id`, adding new content or values. Supported actions: `createAdministrators` `createCollection` `createSubcommunity`	`id, action` - `name` `name`	-	`Id` of newly created entity, depending on the action selected: id of group of administrators id of collection id of subcommunity	`json` `xml`	200, 400, 401, 403, 500
	`PUT`	/communities/{id}/{element}	Update the field `element` of the community `id`. Supported fields: `name` - change name `shortDescription` - change short description `copyrightText` - change copyright text `sidebarText` - change sidebar text `introductoryText` - change introductory text `collections` - add existing collection `children` - add existing subcommunity	`id` `value` `value` `value` `value` `value` `cid` `cid`	-	Response code		200, 400, 401, 403, 500
	`PUT`	`/communities/{id}/logo`	Set the logo for community `id`	`id`	-	Response code	binary	200, 400, 401, 403, 500
•	`DELETE`	`/communities/{id`}	Delete community from the system	`id`	-	Response code	`json` `xml`	200, 400, 401, 403, 500
•	`DELETE`	`/communities/{id}/{element}/{eid`}	Remove attribute/value `eid` of element `element` from the community `id`. Suported elements: `collections` `children` `administrators`	`id, eid` `cid` `cid` -	-	Response code	`json` `xml`
•	`POST`	`/collections`	Action to be done under collection `id`, adding new content or values. Supported actions: `createAdministrators` `createSubmitters` `createTemplateItem` `createWorkflowGroup`	`id, action` - - - `step`	-	Id ow newly created element	`json` `xml`	200, 400, 401, 403, 500
•	`PUT`	`/collections/{id}/{element`}	Update field `element` of the collection `id`. Supported elements: `shortDescription` - short description `introText` - introductory text `copyrightText` - copyright text `sidebarText` - sidebar text `provenance` - provenance `licence` - collection licence `name` - collection name	`id` `value` `value` `value` `value` `value` `value` `value`	-	Response code	`json` `xml`	200, 400, 401, 403, 500
•	`DELETE`	`/collections/{id`}	Delete collection from the system	-	-	Response code	`json` `xml`	200, 400, 401, 403, 500
	`DELETE`	`/collections/{id}/{element}/{cid`}	Remove attribute/value `cid` from collection `id` Supported attributes: `administrators` `item` `submitters` `templateItem`	`id, cid`	`-`	Response code	`json` `xml`
	`PUT`	`/collections/{id}/logo`	Set the logo for collection `id`	`id`		Response code	binary

Content searching

C	Verb	URL	Description	Mandatory parameters	Optional parameters	Sorting fields	Response Data	Formats	Response codes
	`GET`	`/search`	Return a list of all objects found by searching criteria. Notice: community and collection are mutually exclusive options.	-	TBD modifiers{{query=`query`}}&(community=`id` or `collection={{id`}} `idOnly=false`	`id` `name` `lastmodified` `submitter`	Item info with basic metadata for the search results. Additionally return only identifiers when `idOnly=true` is used.	`json` `xml`	200, 204, 400, 500
	`GET`	`/harvest`	Return a list of all objects that have been created, modified or withdrawn within specified time range.	-	`startdate` {enddate}} `community` `collection` `idOnly=false` `withdrawn=false` Notice: community and collection are mutually exclusive options	-	Contains item info including id, name, handle, metadata, bitstreams according to the defined requirements. Additionally when idOnly=true only identifiers of results are returned. If the date is in incompatible format, error 400 is returned.	`json` `xml`	200, 204, 400, 500

Item manipulation

C	Verb	URL	Description	Mandatory parameters	Optional parameters	Response Data	Formats	Response codes
•	`POST`	`/items/{id}/action`	Change parameters of item `id`	`id`	`createBundle` `createSingleBitstream` `removeLicenses` `removeDspaceLicense` `licenseGranted`	Response code	`json` `xml`	200, 400, 401, 403, 500
	`PUT`	`/items/{id`}	Change parameters of an item `id`	-	`isArchived` `isWithdrawn` `owningCollection` `submitter` `owningCollection`
	`PUT`	`/items/{id}/bundles/`	Add an existing bundle `bid` to item `id`	`id` `bid`
	`DELETE`	`/items/{id}/bundles/`	Remove bundle `bid` from item `id`	`id` `bid`
			Set archival status of an item	`id`

	`PUT`	`/items/{id}/metadata`	Add a single metadata field	`id` `element` `value` `schema` `qualifier` `lang`
	`DELETE`	`/items/{id}metadata`	Remove a single metadata field	`schema` `element` `qualifier` `lang`
	`DELETE`	`/items/{id}/metadata`
•	`POST`	`/communities`	Add community to the system	`name`	`logo` `parent` other metadata	`Id` of newly created community	`json` `xml`	200, 400, 401, 403, 500
•	`DELETE`	`/communities/{id}{`}	Delete community from the system	`id`	-	Response code	`json` `xml`	200, 400, 401, 403, 500
•	`PUT`	`/collections/{id}{`}	Change description of `id` collection	`id`		Response code	`json` `xml`	200, 400, 401, 403, 500
•	`POST`	`/collections`	Add collection to the system	`name` `communityId`		`Id` of newly created collection	`json` `xml`	200, 400, 401, 403, 500
•	`DELETE`	`/collections/{id}{`}	Delete collection from the system	-	-	Response code	`json` `xml`	200, 400, 401, 403, 500

User oriented functions

C	Verb	URL	Description	Mandatory parameters	Optional parameters	Sorting fields	Response Data	Formats	Response codes
	`GET`	`/users`	Return a list containing id, name and email of persons.	-	`query` `idOnly=false`	`id` `name` `lastname` `fullname` `language`	List with information on particular user. Additionaly only identifiers are sent if idOnly is true.	`json` `xml`	200, 204, 400, 500

Statistical info

C	Verb	URL	Description	Mandatory parameters	Optional parameters	Sorting fields	Response Data	Formats	Response codes
	`GET`	`/stats`	Return general statistics.	-	-	-	Cummulative list of statistics data for the system currently available.	`json` `xml`	200, 400, 500

Administrative tasks

Workflow related tasks

Relationships interface

C	Verb	URL	Description	Mandatory parameters	Optional parameters	Sorting fields	Response Data	Formats	Response codes
•	GET	/resource/{handle}/relations	Return entities according to relation and parameters specified	`handle` `property`	`rtype` rfield	-	ontains entities selected and sorted in conformance to request parameters. For more details see description of `rtype` and`rfield`.	`json` `xml`	200, 204, 400, 401, 403, 500

Mandatory parameters

Parameter	Description	Values	Example
`property`	Return entities satisfying requested property relation	Structural properties `ds:isPartOfSite` `ds:isPartOfCommunity` `ds:isPartOfCollection` `ds:isPartOfItem` `ds:isPartOfBundle` `ds:hasCommunity` `ds:hasCollection` `ds:hasItem` `ds:hasBundle` `ds:hasBitstream` `ds:hasBitstreamFormat` Communities and collections `ds:logo` Bistream format `ds:support` `ds:fileExtension` `ds:mimeType` Bitstream `ds:messageDigest` `ds:messageDigestAlgorithm` `ds:messageDigestOriginator` `ds:size` Eperson `ds:language`	`property=ds:hasCommunity` - return subcommunities of a community `property=ds:isPartOfCommunity` - return communities current community is part of (children) `property=ds:hasCollection` - return collections belonging to community `property=ds:hasItem` - return Items belonging to community
`rtype`	restriction on type - only entity with specifed type(s) would be returned	`ds:Bitstream` `ds:Bundle` `ds:Collection` `ds:Community` `ds:EPerson` `ds:Group` `ds:Item` `ds:DSpaceObject` `ds:Policy` `ds:Site` `ds:BitstreamFormat`\|	`rtype=ds:Collection` - return entities of Collection type
rfield	restriction on fields - return only selected fields; by default all fields are returned	id name countitems metadata subcommunities ancestors owner other (depending on object type, will be documented later)	rfield=id,name - return only entity id and name in response

Note: incomplete/orientative properties, for more info check [Vocabularies|http://code.google.com/p/dspace-sandbox/source/browse/#svn/modules/dspace-rdf/tags/dspace-rdf-1.5.1/src/main/java/org/dspace/adapters/rdf/vocabularies].

Visitors' suggestions or wishes

Here the visitors and stakeholders can insert their suggestions or describe the needs for their applications in detail.

Comment: In this case it is not clear how to treat recent part of endpoint. If we stick to semantic mapping, then it should look like /resource/id/mapping, but recent in this case obviously do not represent a mapping, but the property.

Comment #2: Semantic mapping presented in this case should be probably hardcoded for 1.x branch, but on abstraction level which enables easy replacement with some auto-discovery method prepared for 2.x and eventually backported to 1.x. This way we would be able to call something similar to /communities/id or communities/id/capabilities in order to get supported mappings (amongst other data).

Integration in the system

It is planned to consult two external subjects for cooperation and the assistance during integration process (LMS and national library internal automation process). More information coming soon - awaiting approval of other parties.

Documentation tasks

Although provided software module exposes basic documentation automatically to the end user, in order to make it easier for other developers and users the documentation in the following forms is additionaly to be provided:

Confluence pages, current location
integrated documentation in PDF form (manual)
short slides containing technology overview, advocacy/facts, configuration and usage guideliens and examples
code will be additionally commented

Example of usage

At the end of the current stage of this project as a bonus task (if time constraints allow) the examples of usage will be provided for several languages, the use-cases will be presented (example of integration in other software, e.g. LMS) and optionally simple client system demonstrating UI customization will be demonstrated (e.g. Flex or JavaFX like).

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GSOC10 - DSpace REST API