Open Archives Initiative - Protocol for Metadata Harvesting - v.2.0 (original) (raw)

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Table of Contents

1. Introduction
2. Definitions and Concepts
2.1. Harvester
2.2. Repository
2.3. Item
2.4. Unique Identifier
2.5. Record
2.5.1 Deleted records
2.6. Set
2.7. Selective Harvesting
2.7.1 Selective Harvesting and Datestamps
2.7.2 Selective Harvesting and Sets
3. Protocol Features
3.1. HTTP Embedding of OAI-PMH requests
3.1.1. HTTP Request Format
3.1.2. HTTP Response Format
3.1.3. Response Compression
3.2. XML Response Format
3.2.1. XML Schema for Validating Responses to OAI-PMH Requests
3.3. UTCdatetime
3.3.1. UTCdatetime in Protocol Requests
3.3.2. UTCdatetime in Protocol Responses
3.4. metadataPrefix and Metadata Schema
3.5. Flow Control
3.5.1 Idempotency of resumptionTokens
3.6. Error and Exception Conditions
4. Protocol Requests and Responses
4.1. GetRecord
4.2. Identify
4.3. ListIdentifiers
4.4. ListMetadataFormats
4.5. ListRecords
4.6. ListSets
5. Dublin Core
6. Implementation Guidelines
Acknowledgements
Document History

1. Introduction

The Open Archives Initiative Protocol for Metadata Harvesting (referred to as the OAI-PMH in the remainder of this document) provides an application-independent interoperability framework based on metadata harvesting. There are two classes of participants in the OAI-PMH framework:

• Data Providers administer systems that support the OAI-PMH as a means of exposing metadata; and
• Service Providers use metadata harvested via the OAI-PMH as a basis for building value-added services.

In this document the key words "must", "must not", "required", "shall", "shall not", "should", " should not", "recommended", "may", and "optional " in bold face are to be interpreted as described in RFC 2119 . An implementation is not conformant if it fails to satisfy one or more of the "must" or "required" level requirements for the protocols it implements.

This document refers in several places to "community-specific" practices to which individual protocol implementations may conform. These practices are described in an accompanying Implementation Guidelines document.

2. Definitions and Concepts

2.1 Harvester

A harvester is a client application that issues OAI-PMH requests. A harvester is operated by a service provider as a means of collecting metadata from repositories.

2.2 Repository

A repository is a network accessible server that can process the 6 OAI-PMH requests in the manner described in this document. A repository is managed by a data provider to expose metadata to harvesters. To allow various repository configurations, the OAI-PMH distinguishes between three distinct entities related to the metadata made accessible by the OAI-PMH.

• resource - A resource is the object or "stuff" that metadata is "about". The nature of a resource, whether it is physical or digital, or whether it is stored in the repository or is a constituent of another database, is outside the scope of the OAI-PMH.
• item - An item is a constituent of a repository from which metadata about a resource can be disseminated. That metadata may be disseminated on-the-fly from the associated resource, cross-walked from some canonical form, actually stored in the repository, etc.
• record - A record is metadata in a specific metadata format. A record is returned as an XML-encoded byte stream in response to a protocol request to disseminate a specific metadata format from a constituent item.

2.3 Item

An item is a constituent of a repository from which metadata about a resource can be disseminated. An item is conceptually a container that stores or dynamically generates metadata about a single resource in multiple formats, each of which can be harvested as records via the OAI-PMH. Each item has an identifier that is unique within the scope of the repository of which it is a constituent.

2.4 Unique Identifier

A unique identifier unambiguously identifies an item within a repository; the unique identifier is used in OAI-PMH requests for extracting metadata from the item. Items may contain metadata in multiple formats. The unique identifier maps to the item, and all possible records available from a single item share the same unique identifier.

The format of the unique identifier must correspond to that of the URI (Uniform Resource Identifier)syntax. Individual communities may develop community-specific URI schemes for coordinated use across repositories. The scheme component of the unique identifiers must not correspond to that of a recognized URI scheme unless the identifiers conform to that scheme. Repositories may implement the oai-identifiersyntax described in the accompanying Implementation Guidelinesdocument.

Unique identifiers play two roles in the protocol:

1. Response: Identifiers are returned by both the ListIdentifiers and ListRecords requests.
2. Request: An identifier, in combination with a metadataPrefix, is used in the GetRecord request as a means of requesting a record in a specific metadata format from an item.

Note that the identifier described here is not that of a resource. The nature of a resource identifier is outside the scope of the OAI-PMH. To facilitate access to the resource associated with harvested metadata, repositories should use an element in metadata records to establish a linkage between the record (and the identifier of its item) and the identifier (URL, URN, DOI, etc.) of the associated resource. The mandatory Dublin Core format provides the identifier element that should be used for this purpose.

2.5 Record

A record is metadata expressed in a single format. A record is returned in an XML-encoded byte stream in response to an OAI-PMH request for metadata from an item. A record is identified unambiguously by the combination of the unique identifier of the item from which the record is available, the metadataPrefixidentifying the metadata format of the record, and the datestampof the record. The XML-encoding of records is organized into the following parts:

• header -- contains the unique identifier of the item and properties necessary for selective harvesting. The header consists of the following parts:
  • the unique identifier -- the unique identifier of an item in a repository;
  • the datestamp -- the date of creation, modification or deletion of the record for the purpose of selective harvesting.
  • zero or more setSpec elements -- the set membership of the item for the purpose of selective harvesting.
  • an optional status attribute with a value of deleted indicates the withdrawal of availability of the specified metadata format for the item, dependent on the repository support for deletions.
• metadata -- a single manifestation of the metadata from an item. The OAI-PMH supports items with multiple manifestations (formats) of metadata. At a minimum, repositories must be able to return records with metadata expressed in the Dublin Core format, without anyqualification. Optionally, a repository may also disseminate other formats of metadata. The specific metadata format of the record to be disseminated is specified by means of an argument -- the metadataPrefix -- in the GetRecord or ListRecords request that produces the record. The [ListMetadataFormats](#ListMetadataFormats) request returns the list of all metadata formats available from a repository, or for a specific item (which can be specified as an argument to the [ListMetadataFormats](#ListMetadataFormats) request).
• about -- an optional and repeatable container to hold data about the metadata part of the record. The contents of an about container must conform to an XML Schema. Individual implementation communities may create XML Schema that define specific uses for the contents of about containers. Two common uses of about containers are:
  • rights statements: some repositories may find it desirable to attach terms of use to the metadata they make available through the OAI-PMH. No specific set of XML tags for rights expression is defined by OAI-PMH, but the about container is provided to allow for encapsulating community-defined rights tags.
  • provenance statements: One suggested use of the about container is to indicate the provenance of a metadata record, e.g. whether it has been harvested itself and if so from which repository, and when. An XML Schema for such a provenance container, as well as some supporting information is available from the accompanying Implementation Guidelines document.

The following example shows an XML-encoding of a recordand its components:

• the header part with:
  • a unique identifier of the item from which the record was disseminated, equal to oai:arXiv.org:cs/0112017;
  • the datestamp of the record equal to 2002-02-28;
  • two setSpecs, respectively cs and math, indicating that the item from which the record was disseminated belongs to two sets of the repository;
• the metadata part. This consists of a single root tag - in the example the tag oai_dc:dc - with the nested tags belonging to the corresponding metadata format - in the example, Dublin Core elements such as dc:title. Note that the root tag within the metadata part includes a number of attributes that are common to all XML documents that use namespaces and schema validity:
  • namespace declarations -- the declarations of the namespaces used within the metadata part, each of which is prefixed with xmlns. Namespace declarations within the metadata part fall into two categories:
    * metadata format specific namespace(s) - every metadata part must include one or more xmlns prefixed attributes that define the correspondence between a metadata format prefix -- e.g. dc -- and the namespace URI (as defined by the XML namespace specification ) of the respective metadata format. Some metadata formats employ tags from multiple namespaces, requiring multiple xmlns prefixed attributes -- in the example, there are declarations for both oai_dc and dc.
    * xml schema namespace - every metadata part must include the attribute xmlns:xsi, the value of which must always be the URI shown in the example, which is the namespace URI for XML schema.
  • xsi:schemaLocation -- the value of which is a URI, URL pair; the first is the namespace URI (as defined by the XML namespace specification) of the metadata that follows in this part, and the second is the URL of the XML schema for validation of the metadata that follows.
• one about part of the record which uses the oai_provenance.xsd schema, described in the accompanying Implementation Guidelines document, as a means to provide information regarding the origins of the metadata part of the record. Note that the root element within each about part has the same structure as the root element in the metadata part.

2.5.1 Deleted records

If a record is no longer available then it is said to be deleted. Repositories must declare one of three levels of support for deleted records in the deletedRecord element of theIdentify response:

• no - the repository does not maintain information about deletions. A repository that indicates this level of support must not reveal a deleted status in any response.
• persistent - the repository maintains information about deletions with no time limit. A repository that indicates this level of support must persistently keep track of the full history of deletions and consistently reveal the status of a deleted record over time.
• transient - the repository does not guarantee that a list of deletions is maintained persistently or consistently. A repository that indicates this level of support may reveal a deleted status for records.

If a repository does not keep track of deletions then such records will simply vanish from responses and there will be no way for a harvester to discover deletions through continued incremental harvesting. If a repository does keep track of deletions then the datestamp of the deleted record must be the date and time that it was deleted. Responses to [GetRecord](#GetRecord) request for a deleted record must then include a [header](#header) with the attribute status="deleted", and must not include metadata or about parts. Similarly, responses to selective harvestingrequests with set membership and date range criteria that include deleted records must include the headers of these records. Incremental harvesting will thus discover deletions from repositories that keep track of them.

Deleted status is a property of individual records. Like a normal record, a deleted record is identified by a unique identifier, ametadataPrefix and a datestamp. Other records, with different metadataPrefix but the same unique identifier, may remain available for the item.

2.6 Set

A set is an optional construct for grouping items for the purpose of selective harvesting. Repositories may organize items into sets. Set organization may be flat, i.e. a simple list, or hierarchical. Multiple hierarchies with distinct, independent top-level nodes are allowed. Hierarchical organization of sets is expressed in the syntax of the setSpec parameter as described below. When a repository defines a set organization it must include set membership information in the headersof items returned in response to the ListIdentifiers , ListRecords and GetRecord requests.

Each node in a set organization of a repository has:

• a setSpec -- a colon [:] separated list indicating the path from the root of the set hierarchy to the respective node. Each element in the list is a string consisting of any valid URI unreserved characters, which must not contain any colons [:]. Since a setSpec forms a unique identifier for the set within the repository, it must be unique for each set. Flat set organizations have only sets with setSpec that do not contain any colons [:].
• a setName -- a short human-readable string naming the set.
• a setDescription -- an optional and repeatable container that may hold community-specific XML-encoded data about the set; the accompanying Implementation Guidelines document provides suggestions regarding the usage of this container.

The following is an example of a possible set hierarchy in a repository:

• Institutions
  • Oceanside University of Nebraska
  • Valley View University of Florida
• Subjects
  • Existential Kenesiology
  • Quantum Psychology

The following table shows a possible representation of the above set hierarchy by means of setName and respective setSpec values.

An item may be organized in one set, several sets, or no sets at all. In the example above, it is conceivable that an individual item is organized in both subject and institution:florida. A harvester should not assume that harvesting every set in a repository will retrieve metadata from all items in the repository. Items may also be assigned to interior nodes in the set hierarchy.

The actual meaning of a set or of the arrangement of sets in a repository is not defined in the protocol. It is expected that individual communities may formulate well-defined set configurations with perhaps a controlled vocabulary for setNamesand setSpec , and may even develop mechanisms for exposing these to harvesters. For example, a group of cooperating e-print archives in a specific discipline may agree on sets that arrange metadata in their repositories based on a controlled subject classification.

A repository's set hierarchy is represented in the protocol via setSpecs. [ListSets](#ListSets)returns a list indicating the configuration of sets in a repository. Each member of this list must include a setSpecand a setName and may include a setDescription. ListRecordsand [ListIdentifiers](#ListIdentifiers) requests may include an optional set argument, the value of which is a setSpec, to specify the target set for selective harvesting. In the previous example of a set hierarchy, the setSpec institution:nebraska could be used in a request to return only those records that are disseminated from items organized in the set represented by this setSpec. Five issues should be noted here:

• If a repository supports sets then it must include set membership information in response to ListIdentifiers,ListRecords and GetRecord requests. The list of setSpec elements should include only the minimum number of setSpec elements required to specify the set membership. Using the previous example of a set hierarchy, the header for an item organized in set institution:florida should not include setSpec institution since that is implied by the setSpec institution:florida.
• An item may be organized in more than one set; meaning that different setSpec arguments may return the same record(s).
• An item need not be organized in any set; meaning that an exhaustive repetition of [ListRecords](#ListRecords) requests with all possible setSpecs is not guaranteed to return all records in the repository. The only guaranteed methods of harvesting all records or headers are [ListRecords](#ListRecords) or [ListIdentifiers](#ListIdentifiers) requests with no setSpec argument.
• When a setSpec is used as an argument, the response must include records or headers from all items in the set specified by the setSpec , and all records or headers from items in sets that are descendant from the specified set. Using the previous example of a set hierarchy, a setSpec of institution to the [ListRecords](#ListRecords) request will return all records from metadata organized within the set with a setSpec value equal to institution and within the descendent sets with setSpec values equal to institution:florida and institution:nebraska.
• The set hierarchy of a repository may include sets that are empty.

2.7 Selective Harvesting

Selective harvesting allows harvesters to limit harvest requests to portions of the metadata available from a repository. The OAI-PMH supports selective harvesting with two types of harvesting criteria that may be combined in an OAI-PMH request: datestamps and set membership.

2.7.1 Selective Harvesting and Datestamps

Harvesters may use datestamps to harvest only those records that were created, deleted, or modified within a specified date range. To specify datestamp-based selective harvesting, datestamps are included as values of the optional arguments, from and until, in the ListRecords andListIdentifiersrequests. Harvesting is restricted to the range specified by the fromand until arguments, extending back to the earliest datestamp if from is omitted, and forward to the most recent datestamp if until is omitted. Range limits are inclusive: from specifies a bound that must be interpreted as "greater than or equal to", until specifies a bound that must be interpreted as "less than or equal to". Therefore, the fromargument must be less than or equal to the untilargument. Otherwise, a repository must issue a badArgumenterror.

Repositories must support selective harvesting with the fromand until arguments expressed at day granularity. Optional support for seconds granularity is indicated in the response to the Identifyrequest. The value of datestamps in both requests and responses must comply to the specifications for UTCdatetime in this document. A repository must update the datestamp of a record if a change occurs, the result of which would be a change to the metadata part of the XML-encoding of the record. Such changes include, but are not limited to, changes to the metadata of the record, changes to the metadata format of the record, introduction of a new metadata format, termination of support for a metadata format, etc.

Datestamp ranges for selective harvesting are expressed in the fromand until arguments that maybe submitted in the ListRecordsand ListIdentifiers requests. Repositories must use the following rules to create a ListRecordsresponse matching the specified datestamp range according to the type of change that occurred within the repository. The response to a [ListIdentifiers](#ListIdentifiers) request follows the same rules but is abbreviated to include only headers rather than records.

• modification - the response must include records, corresponding to the metadataPrefix argument, which have changed within the bounds of the from and until arguments.
• creation - the response must include records, corresponding to the metadataPrefix argument, that have become available from the repository within the bounds of the from and until arguments.
• deletion - depending on the level at which a repository keeps track of deleted records, the response may include headers of records, corresponding to the metadataPrefix argument, which have been withdrawn from the repository within the bounds of the from and until arguments. Deleted status is indicated via the status attribute of the header element and no metadata is included.

Every header returned by the GetRecord, ListRecordsor ListIdentifiersrequests contains a datestamp, which reflects the most recent date and time of the creation, modification, or deletion according to the rules defined above.

2.7.2 Selective Harvesting and Sets

Harvesters may specify set membership as a criteria for selective harvesting. To specify set-based selective harvesting, a setSpec is included as the value of the optional set argument to the ListRecordsand ListIdentifiersrequests, thereby specifying selective harvesting of records from items within the respective set.

When a setSpec is used as an argument, the response must include:

• the records corresponding to the metadataPrefix argument, or headers thereof in the case of deleted records, available from those items in the set specified by the setSpec;
• the records corresponding to the metadataPrefix argument, or headers thereof in the case of deleted records, available from those items in sets that are descendant from the specified set.

3. Protocol Features

3.1 HTTP Embedding of OAI-PMH requests

OAI-PMH requestsare expressed as HTTPrequests. A typical implementation uses a standard Web server that is configured to dispatch OAI-PMH requests to the software handling these requests. The remainder of this section describes the aspects of the protocol that are specific to the HTTP embedding.

3.1.1 HTTP Request Format

OAI-PMH requests must be submitted using either the HTTP GET or POST methods. POST has the advantage of imposing no limitations on the length of arguments. Repositories mustsupport both the GET and POST methods. There is a single base URL for all requests. The base URL specifies the Internet host and port, and optionally a path, of an HTTP server acting as a repository. Repositories expose their base URL as the value of the baseURL element in the Identify response. Note that the composition of any path is determined by the configuration of the repository's HTTP server.

In addition to the base URL, all requests consist of a list of keyword arguments, which take the form of key=value pairs. Arguments may appear in any order and multiple arguments must be separated by ampersands [&]. Each OAI-PMH request must have at least one key=value pair that specifies the OAI-PMH request issued by the harvester:

• key is the string 'verb';
• value is one of the defined OAI-PMH requests.

The number and nature of additional key=value pairs depends on the arguments for the individual request.

3.1.1.1 Encoding an OAI-PMH request in a URL for an HTTP GET

URLs for GET requests have keyword arguments appended to the base URL, separated from it by a question mark [?]. For example, the URL of a [GetRecord](#GetRecord)request to a repository with base URL that is http://an.oa.org/OAI-scriptmight be:

http://an.oa.org/OAI-script? verb=GetRecord&identifier=oai:arXiv.org:hep-th/9901001&metadataPrefix=oai_dc

However, since special characters in URIs must be encoded, the correct form of the above GET request URL is:

http://an.oa.org/OAI-script? verb=GetRecord&identifier=oai%3AarXiv.org%3Ahep-th%2F9901001&metadataPrefix=oai_dc

3.1.1.2 Encoding an OAI-PMH request in an HTTP POST

Keyword arguments are carried in the message body of the HTTP POST. The Content-Type of the request must be application/x-www-form-urlencoded. For example, submitting the same request as above using the POST method would use just the base URL as the URL, with the format of the POST being:

`POST http://an.oa.org/OAI-script HTTP/1.0
Content-Length: 82
Content-Type: application/x-www-form-urlencoded

verb=GetRecord&identifier=oai%3AarXiv.org%3Ahep-th%2F9901001&metadataPrefix=oai_dc

`

3.1.1.3 Encoding of special characters in keyword arguments of OAI-PMH requests

The syntax rules for URIsrestrict a few characters to special roles in certain contexts, and require that if these characters are used in any other way that they must be written as an escape sequence, i.e. a percent sign followed by the character code in hexadecimal. The reserved characters include:

As a result, these characters must be represented by their respective escape sequence if their use does not correspond to their established URI role. In case of the OAI-PMH, this means that the reserved characters must be encoded when they appear in the valuepart of the key=value pairs of the request. This applies for both the GET and POSTencoding of the OAI-PMH requests.

3.1.2 HTTP Response Format

Responses to requests are formatted as HTTP responses, with appropriate HTTP header fields.

3.1.2.1 Content-Type

The Content-Type returned for all OAI-PMH requests must be text/xml.

3.1.2.2 Status-Code

OAI-PMH errors are distinguished from HTTP Status-Codes. Since OAI-PMH uses HTTP as a transport layer, servers implementing OAI-PMH must conform to HTTP status code definitionsand report relevant HTTP transport layer status via those Status-Codes. OAI-PMH repositories may employ HTTP Status-Codes in addition to "200 OK". For instance, the following Status-Codesmay be useful for load balancing in OAI repositories:

• 302 - Allows the repository to temporarily redirect an OAI-PMH request to another repository. The URI of the temporary repository should be given by the Location field in the HTTP response.
• 503 - Service unavailable, a Retry-After period is specified. Harvesters should wait this period before attempting another OAI-PMH request.

3.1.3 Response Compression

Response compression is optional in OAI-PMH. Compression of responses to OAI-PMH requests is handled at the level of HTTP, with the following restrictions:

• Harvesters may include an Accept-Encoding header in their OAI-PMH requests to specify response compression preferences.
• Harvesters that do not include an Accept-Encoding header in their requests will always receive uncompressed responses.
• When a request includes an Accept-Encoding header the list of encodings must include the identity (no compression) encoding (with a non-zero qvalue).
• Repositories must support the HTTP identity encoding.
• Repositories should express the encodings they support in addition to identity by including compression elements in the [Identify](#Identify) response.

3.2 XML Response Format

All responses to OAI-PMH requests must be well-formed XML instance documents. Encoding of the XML must use the UTF-8 representation of Unicode. Character references, rather than entity references, mustbe used. Character references allow XML responses to be treated as stand-alone documents that can be manipulated without dependency on entity declarations external to the document.

The XML data for all responses to OAI-PMH requests must validate against the XML Schema shown at the end of this section . As can be seen from that schema, responses to OAI-PMH requests have the following common markup:

1. The first tag output is an XML declaration where the version is always 1.0 and the encoding is always UTF-8, eg: <?xml version="1.0" encoding="UTF-8" ?>
2. The remaining content is enclosed in a root element with the name OAI-PMH. This element must have three attributes that define the XML namespaces used in the remainder of the response and the location of the validating schema:
   • xmlns -- the value of which must be the namespace URI of the OAI-PMH (http://www.openarchives.org/OAI/2.0/).
   • xmlns:xsi -- the value of which must be the namespace URI for XML schema (http://www.w3.org/2001/XMLSchema-instance).
   • xsi:schemaLocation -- is a pair, the first part of which is the namespace URI (as defined by the XML namespace specification ) of the OAI-PMH (http://www.openarchives.org/OAI/2.0/), and the second part is the URL of the XML schema for validation of the response (http://www.openarchives.org/OAI/2.0/OAI-PMH.xsd).
3. For all responses, the first two children of the root element are:
   • responseDate -- a UTCdatetime indicating the time and date that the response was sent. This must be expressed in UTC.
   • request -- indicating the protocol request that generated this response. The rules for generating the request element are as follows:
     * The content of the request element must always be the base URL of the protocol request;
     * The only valid attributes for the request element are the keys of the key=value pairs of protocol request. The attribute values must be the corresponding values of those key=value pairs;
     * In cases where the request that generated this response did not result in an error or exception condition, the attributes and attribute values of the request element must match the key=value pairs of the protocol request;
     * In cases where the request that generated this response resulted in a badVerb or badArgument error condition, the repository must return the base URL of the protocol request only. Attributes must not be provided in these cases.
4. The third child of the root element is either:
   • an error element that must be used in case of an error or exception condition;
   • an element with the same name as the verb of the respective OAI-PMH request.

An example of a successful reply to the GetRecord request shown above is of the form:

2002-05-01T19:20:30Z http://an.oa.org/OAI-script ...

3.2.1 XML Schema for Validating Responses to OAI-PMH Requests

3.3 UTCdatetime

Dates and times are uniformly encoded using ISO8601 and are expressed in UTC throughout the protocol. When time is included, the special UTC designator ("Z") must be used. UTC is implied for dates although no timezone designator is specified. For example, 1957-03-20T20:30:00Z is UTC 8:30:00 PM on March 20th 1957. UTCdatetime is used in both protocol requests and protocol replies, in the way described in the following sections.

3.3.1 UTCdatetime in Protocol Requests

Datestamps used as values of the optional arguments from and until in the [ListIdentifiers](#ListIdentifiers) and [ListRecords](#ListRecords) requests are encoded using ISO8601 and are expressed in UTC. These arguments are used to specify datestamp-based selective harvesting. These arguments support the "Complete date" and the "Complete date plus hours, minutes and seconds" granularities defined in ISO8601. The legitimate formats are YYYY-MM-DD and YYYY-MM-DDThh:mm:ssZ. Both arguments must have the same granularity. All repositories must support YYYY-MM-DD. A repository that supports YYYY-MM-DDThh:mm:ssZ should indicate so in the [Identify](#Identify)response. A request by a harvester with finer granularity than that supported by a repository must produce an error.

3.3.2 UTCdatetime in Protocol Responses

Datestamps appear in the headers of records that are returned in response to ListIdentifiers , [GetRecord](#GetRecord) and [ListRecords](#ListRecords) requests. These datestamps are encoded using ISO8601and are expressed in UTC; they must be expressed in the finest granularity supported by the repository. The value of the datestamp must correspond to the rules for datestamp-based selective harvesting.

Each protocol response includes a responseDate element, which must be the time and date of the response in UTC. This is encoded using the "Complete date plus hours, minutes, and seconds" variant of ISO8601. This format is YYYY-MM-DDThh:mm:ssZ.

A [resumptionToken](#FlowControl) in a protocol reply may include an optional argument expirationDate, which is expressed in UTC. This is encoded using the "Complete date plus hours, minutes, and seconds" variant of ISO8601. This format is YYYY-MM-DDThh:mm:ssZ.

3.4 metadataPrefix and Metadata Schema

OAI-PMH supports the dissemination of records in multiple metadata formats from a repository. The [ListMetadataFormats](#ListMetadataFormats) request returns the list of all metadata formats available from a repository, each of which has the following properties:

• The metadataPrefix - a string to specify the metadata format in OAI-PMH requests issued to the repository. metadataPrefix consists of any valid URI unreserved characters.metadataPrefix arguments are used in ListRecords, ListIdentifiers, and [GetRecord](#GetRecord) requests to retrieve records, or the headers of records that include metadata in the format specified by the metadataPrefix;
• The metadata schema URL - the URL of an XML schema to test validity of metadata expressed according to the format;
• The XML namespace URI that is a global identifier of the metadata format.

The metadata in each record returned by [ListRecords](#ListRecords) and [GetRecord](#GetRecord) must comply with the conventions of the XML namespace specification. This means that the root element of the metadata part mustcontain an xmlns attribute, the value of which is the XML namespace URI of the metadata format. The root element must also contain an xsi:schemaLocation attribute that has a value that includes the URL of the XML schema for validation of the metadata. This URL must match the URL of the metadata schema for the metadataPrefix included as an argument to the [ListRecords](#ListRecords) or [GetRecord](#GetRecord) request (the mapping from metadataPrefix to metadata schema is defined by the repository's response to the [ListMetadataFormats](#ListMetadataFormats)request).

For purposes of interoperability, repositories must disseminate Dublin Core, without any qualification. Therefore, the protocol reserves the metadataPrefix ` oai_dc', and the URL of a metadata schema for unqualified Dublin Core, which is http://www.openarchives.org/OAI/2.0/oai_dc.xsd. The corresponding XML namespace URI is http://www.openarchives.org/OAI/2.0/oai\_dc/.

The metadataPrefix ` all' is reserved for future use. Implementations **should not** use this metadataPrefix.

Communities should adopt guidelines for sharing of metadataPrefixes,metadata schema and XML namespace URI's of metadata formats. Such guidelines are outside of the scope of the OAI-PMH. The accompanying Implementation Guidelinesdocument provides some sample XML Schema and instance documents for common metadata formats such as MARC and RFC 1807.

3.5 Flow Control

A number of OAI-PMH requests return a list of discrete entities: [ListRecords](#ListRecords) returns a list of records, [ListIdentifiers](#ListIdentifiers) returns a list of headers, and [ListSets](#ListSets)returns a list of sets. Collectively these requests are called list requests. In some cases, these lists may be large and it may be practical to partition them among a series of requests and responses. This partitioning is accomplished as follows:

• A repository replies to a request with an incomplete list and a resumptionToken;
• In order to make the response a complete list, the harvester will need to issue one or more requests with resumptionTokens as arguments. The complete list then consists of the concatenation of the incomplete lists from the sequence of requests, known as a list request sequence.

Details of flow control and the resumptionToken are as follows:

• The only defined use of resumptionToken is as follows:
  • a repository must include a resumptionToken element as part of each response that includes an incomplete list;
  • in order to retrieve the next portion of the complete list, the next request must use the value of that resumptionToken element as the value of the resumptionToken argument of the request;
  • the response containing the incomplete list that completes the list must include an empty resumptionToken element;
    All other uses of resumptionToken by a harvester are illegal and must return an error.
• In all cases when a resumptionToken is issued, the incomplete list must consist of complete entities; e.g., all individual records returned in an incomplete record list from a ListRecords request must be intact.
• The format of the resumptionToken is not defined by the OAI-PMH and should be considered opaque by the harvester.
• The protocol does not define the semantics of incompleteness. Therefore, a harvester should not assume that the members in an incomplete list conform to some selection criteria (e.g., date ordering).
• Before including a resumptionToken in the URL of a subsequent request, a harvester must encode any special characters in it.

The following optional attributes may be included as part of the resumptionTokenelement along with the resumptionToken itself:

• expirationDate -- a UTCdatetime indicating when the resumptionToken ceases to be valid.
• completeListSize -- an integer indicating the cardinality of the complete list (i.e., the sum of the cardinalities of the incomplete lists). Because there may be changes in a repository during a list request sequence, as described under Idempotency of resumptionTokens, the value of completeListSize may be only an estimate of the actual cardinality of the complete list and may be revised during the list request sequence.
• cursor -- a count of the number of elements of the complete list thus far returned (i.e. cursor starts at 0).

The following example is a series of ListRecords requests where the complete list consists of 175 records and the repository only returns 100 records per response.

• The harvester issues a ListRecords request.
• The repository responds with an incomplete list of 100 records. The repository marks this list as incomplete by including in the response a non-emptyresumptionTokenelement, with two attributes: a completeListSize of 175, and a cursor of 0.
• The harvester issues a subsequent ListRecords request that includes the resumptionToken that it received in the previous response.
• The repository responds with an incomplete list of 75 records. The repository marks this list as the final incomplete list by including in the response an empty resumptionToken element with two attributes: a completeListSize of 175, and a cursor of 100.

This flow control mechanism, in combination with HTTP transport layer facilities, provides some basic tools with which a repository can enforce an acceptable use policy for its harvesting interface. Communities implementing the OAI-PMH may need more extensive tools to enforce acceptable use policies for either the harvesting interface of their repositories or for the metadata harvested from those repositories. The enforcement of such additional policies is outside of the scope of the OAI-PMH.

3.5.1 Idempotency of resumptionTokens

Repositories that implement resumptionTokens must do so in a manner that allows harvesters to resume a sequence of requests for incomplete lists by re-issuing a list request with the most recent resumptionToken. The purpose of this is to allow harvesters to recover from network or other errors that would otherwise mean that the list request sequence would have to be started again. A re-issue of a list request with a resumptionToken occurs in two contexts:

1. When there are no changes in the repository. There are no changes to the complete list returned by the list request sequence. In this case, the repository must return the same incomplete list when the most recent list request, i.e. the one with the most recent non-expired resumptionToken, is re-issued.
2. When there are changes in the repository. There may be changes to the complete list returned by the list request sequence. These changes occur when the records disseminated in the list move in or out of the datestamp range of the request because of changes, modifications, or deletions in the repository. In this case, strict idempotency of the incomplete-list requests using resumptionToken values is not required. Instead, the incomplete list returned in response to a re-issued request must include all records with unchanged datestamps within the range of the initial list request. The incomplete list returned in response to a re-issued request may contain records with datestamps that either moved into or out of the range of the initial request. In cases where there are substantial changes to the repository, it may be appropriate for a repository to return a badResumptionToken error, signaling that the harvester should restart the list request sequence.

3.6 Error and Exception Conditions

In event of an error or exception condition, repositories mustindicate OAI-PMH errors, distinguished from HTTP Status-Codes, by including one or more error elements in the response. While one error element is sufficient to indicate the presence of the error or exception condition, repositories should report all errors or exceptions that arise from processing the request. Each error element must have a codeattribute that must be from the following table; each error element mayalso have a free text string value to provide information about the error that is useful to a human reader. These strings are not defined by the OAI-PMH.

The following example demonstrates error handling in the case of an illegal verb argument. All request URLs shown from now on will be wrapped to make them more readable.

Request

http://arXiv.org/oai2? verb=nastyVerb

Response

2002-05-01T09🔞29Z http://arXiv.org/oai2 Illegal OAI verb

The following example demonstrates error handling in the case of a ListSets request to a repository that does not handle sets.

Request

http://arXiv.org/oai2? verb=ListSets

Response

2002-05-01T09🔞29Z http://arXiv.org/oai2 This repository does not support sets

4. Protocol Requests and Responses

This section lists the requests, or verbs, defined in the OAI-PMH. The documentation for each request is organized as follows:

• A section title corresponding to the token used to specify the request as the required verb argument to an HTTP request.
• A brief summary of the meaning of the verb and notes on its usage.
• The list of additional arguments for the request. Arguments are of three types:
  • required, the argument must be included with the request (the verb argument is always required, as described in HTTP Request Format).
  • optional, the argument may be included with the request.
  • exclusive, the argument may be included with request, but must be the only argument (in addition to the verb argument).
• Error and exception conditions specific to the protocol request.
• One or more example requests and corresponding responses, with explanatory notes if appropriate.

An XML Schema defines the format of valid replies to all OAI-PMH requests.

4.1 GetRecord

Summary and Usage Notes

This verb is used to retrieve an individual metadata record from a repository. Required arguments specify the identifier of the item from which the record is requested and the format of the metadata that should be included in the record. Depending on the level at which a repository tracks deletions, a header with a "deleted" value for the statusattribute may be returned, in case the metadata format specified by the metadataPrefix is no longer available from the repository or from the specified item.

Arguments

• **identifier** a required argument that specifies the unique identifier of the item in the repository from which the record must be disseminated.
• **metadataPrefix** a required argument that specifies the metadataPrefix of the format that should be included in the metadata part of the returned record . A record should only be returned if the format specified by the metadataPrefix can be disseminated from the item identified by the value of the identifier argument. The metadata formats supported by a repository and for a particular record can be retrieved using the [ListMetadataFormats](#ListMetadataFormats) request.

Error and Exception Conditions

• **badArgument** - The request includes illegal arguments or is missing required arguments.
• **cannotDisseminateFormat** - The value of the metadataPrefix argument is not supported by the item identified by the value of the identifier argument.
• **idDoesNotExist** - The value of the identifier argument is unknown or illegal in this repository.

Examples

Request

Request a record in the Dublin Core metadata format [URL shown without encoding to be more readable].

http://arXiv.org/oai2? verb=GetRecord&identifier=oai:arXiv.org:cs/0112017&metadataPrefix=oai_dc

Response

2002-02-08T08:55:46Z http://arXiv.org/oai2

Request

Request a record in the Dublin Core metadata format. The requested record, however, can not be returned because the identifier does not exist. Therefore, the response does not contain a recordcontainer. It does have an error element with a code attribute that has the value idDoesNotExist. [URL shown without encodingfor better readability].

http://arXiv.org/oai2? verb=GetRecord&identifier=oai:arXiv.org:quant-ph/02131001&metadataPrefix=oai_dc

Response

2002-02-08T08:55:46Z http://arXiv.org/oai2 No matching identifier in arXiv

Request

Request a record in the oai_marc metadata format. However, the requested metadata format can not be disseminated for this identifier. Therefore, the response contains no record. It does contain an error element with a codeattribute that has the value cannotDisseminateFormat. [URL shown without encodingfor better readability].

http://arXiv.org/oai2? verb=GetRecord&identifier=oai:arXiv.org:quant-ph/9901001&metadataPrefix=oai_marc

Response

2002-02-08T08:55:46Z http://arXiv.org/oai1

4.2 Identify

Summary and Usage Notes

This verb is used to retrieve information about a repository. Some of the information returned is required as part of the OAI-PMH. Repositories may also employ the Identify verb to return additional descriptive information.

Arguments

None

Error and Exception Conditions

• **badArgument** - The request includes illegal arguments.

Response Format

The response must include one instance of the following elements:

• repositoryName : a human readable name for the repository;
• baseURL : the base URL of the repository;
• protocolVersion : the version of the OAI-PMH supported by the repository;
• earliestDatestamp : a UTCdatetime that is the guaranteed lower limit of all datestamps recording changes, modifications, or deletions in the repository. A repository must not use datestamps lower than the one specified by the content of the earliestDatestamp element.earliestDatestamp must be expressed at the finest granularity supported by the repository.
• deletedRecord : the manner in which the repository supports the notion of deleted records. Legitimate values are no ; transient ; persistent with meanings defined in the section on deletion.
• granularity: the finest harvesting granularity supported by the repository. The legitimate values are YYYY-MM-DD and YYYY-MM-DDThh:mm:ssZ with meanings as defined in ISO8601.

The response must include one or more instances of the following element:

• adminEmail : the e-mail address of an administrator of the repository.

The response may include multiple instances of the following optional elements:

• compression : a compression encoding supported by the repository. The recommended values are those defined for the Content-Encoding header in Section 14.11 of RFC 2616 describing HTTP 1.1. A compression element should not be included for the identity encoding, which is implied.
• description : an extensible mechanism for communities to describe their repositories. For example, the description container could be used to include collection-level metadata in the response to the Identify request. Implementation Guidelines are available to give directions with this respect. Each description container must be accompanied by the URL of an XML schema describing the structure of the description container.

Examples

Request

http://memory.loc.gov/cgi-bin/oai? verb=Identify

Response

The below example of a response to the Identify request contains three description containers:

• The oai-identifier container complies to an XML Schema, which is available at http://www.openarchives.org/OAI/2.0/oai-identifier.xsd. This schema, provided in the accompanying Implementation Guidelines document, is used by repositories that choose to comply with a specific format of unique identifiers for items. The format of that identifier is explained by means of comments in the oai-identifier.xsd XML Schema.
• The eprints container complies to an XML Schema, which is available at http://www.openarchives.org/OAI/1.1/eprints.xsd. This schema, provided in the accompanying Implementation Guidelines document, has been agreed upon by the OAI e-print community, and contains information specific to repositories in that community.
• The friends container complies to an XML Schema, which is available at http://www.openarchives.org/OAI/2.0/friends.xsd. This schema, provided in the accompanying Implementation Guidelines document, is used by repositories that want to point harvesters to other repositories, by listing their base URLs. Usage of the friends container is recommended; it may support harvesters in discovering the network-location of repositories.

2002-02-08T12:00:01Z http://memory.loc.gov/cgi-bin/oai Library of Congress Open Archive Initiative Repository 1 http://memory.loc.gov/cgi-bin/oai 2.0 somebody@loc.gov anybody@loc.gov 1990-02-01T12:00:00Z transient YYYY-MM-DDThh:mm:ssZ deflate oai lcoa1.loc.gov : oai:lcoa1.loc.gov:loc.music/musdi.002 http://memory.loc.gov/ammem/oamh/lcoa1_content.html Selected collections from American Memory at the Library of Congress http://oai.east.org/foo/ http://oai.hq.org/bar/ http://oai.south.org/repo.cgi

4.3 ListIdentifiers

Summary and Usage Notes

This verb is an abbreviated form of ListRecords, retrieving only headers rather than records. Optional arguments permit selective harvesting of headers based on set membership and/or datestamp. Depending on the repository's support for deletions, a returned header may have a status attribute of "deleted" if a record matching the arguments specified in the request has been deleted.

Arguments

• **from** an optional argument with a UTCdatetime value, which specifies a lower bound for datestamp-based selective harvesting.
• **until** an optional argument with a UTCdatetime value, which specifies a upper bound for datestamp-based selective harvesting.
• **metadataPrefix** a required argument, which specifies that headers should be returned only if the metadata format matching the supplied metadataPrefix is available or, depending on the repository's support for deletions, has been deleted. The metadata formats supported by a repository and for a particular item can be retrieved using the ListMetadataFormats request.
• **set** an optional argument with a setSpec value , which specifies set criteria for selective harvesting.
• **resumptionToken** an exclusive argument with a value that is the flow control token returned by a previous [ListIdentifiers](#ListIdentifiers) request that issued an incomplete list.

Error and Exception Conditions

• **badArgument** - The request includes illegal arguments or is missing required arguments.
• **badResumptionToken** - The value of the resumptionToken argument is invalid or expired.
• **cannotDisseminateFormat** - The value of the metadataPrefix argument is not supported by the repository.
• **noRecordsMatch**- The combination of the values of the from, until, and set arguments results in an empty list.
• **noSetHierarchy** - The repository does not support sets.

Examples

Request

List the headers of records in the oldArXiv metadata format that are added, modified or deleted since January 15, 1998 in the set physics:hep. [URL shown without encoding for better readability].

http://an.oa.org/OAI-script? verb=ListIdentifiers&from=1998-01-15&metadataPrefix=oldArXiv&set=physics:hep

Response

A list of four headers is returned. One header has a deletedstatus, indicating that a record in the metadata format specified by the metadataPrefix is no longer available. In addition, a resumptionToken (non-empty, value xxx45abttyz) has been returned, indicating that the list of headers is incomplete and that one or more subsequent requests will need to be issued to retrieve a _complete_list. In the example, the resumptionToken comes with all of the 3 optional attributes: expirationDate indicates that the resumptionToken will become unusable after 11:20 PM UTC on June 1st 2002; completeListSize indicates that the complete list consists of 6 identifiers; the zero-value for cursor indicates that no headers have been returned previous to this reply.

2002-06-01T19:20:30Z http://an.oa.org/OAI-script

Request

Issue a subsequent request to the one issued above. The single resumptionToken argument has the value returned in the previous response. [URL shown without encodingfor better readability].

http://an.oa.org/OAI-script? verb=ListIdentifiers&resumptionToken=xxx45abttyz

Response

Two more headers are returned. The resumptionToken element at the end of the list has no value, indicating that the list is now complete. The value of the completeListSize attribute remains 6, while the value of the cursor attribute has changed to 4, indicating that a previous reply has (or previous replies have) already delivered 4 identifiers.

2002-06-01T19:30:00Z http://an.oa.org/OAI-script

Request

List the headers of olac-formatted records, added or modified on January 1, 2001 in the set Perseus:collection:PersInfo. There are no matches for this request, hence, the response contains an error tag and does not contain any header elements [URL shown without encoding for better readability].

http://www.perseus.tufts.edu/cgi-bin/pdataprov? verb=ListIdentifiers&metadataPrefix=olac&from=2001-01-01&until=2001-01-01 &set=Perseus:collection:PersInfo

Response

2002-02-08T14:27:19Z http://www.perseus.tufts.edu/cgi-bin/pdataprov

4.4 ListMetadataFormats

Summary and Usage Notes

This verb is used to retrieve the metadata formats available from a repository. An optional argument restricts the request to the formats available for a specific item.

Arguments

• **identifier** an optional argument that specifies the unique identifier of the item for which available metadata formats are being requested. If this argument is omitted, then the response includes all metadata formats supported by this repository. Note that the fact that a metadata format is supported by a repository does not mean that it can be disseminated from all items in the repository.

Error and Exception Conditions

• **badArgument** - The request includes illegal arguments or is missing required arguments.
• **idDoesNotExist** - The value of the identifier argument is unknown or illegal in this repository.
• **noMetadataFormats** - There are no metadata formats available for the specified item.

Examples

Request

List the metadata formats that can be disseminated from the repository http://www.perseus.tufts.edu/cgi-bin/pdataprov for the item with unique identifier oai:perseus.tufts.edu:Perseus:text:1999.02.0119 [URL shown without encodingfor better readability].

http://www.perseus.tufts.edu/cgi-bin/pdataprov? verb=ListMetadataFormats&identifier=oai:perseus.tufts.edu:Perseus:text:1999.02.0119

Response

The response shows that 3 metadata formats are supported for the given identifier: oai_dc, olac and perseus. For each of the formats, the location of an XML Schema describing the format, as well as the XML Namespace URI is given.

2002-02-08T14:27:19Z http://www.perseus.tufts.edu/cgi-bin/pdataprov oai_dc http://www.openarchives.org/OAI/2.0/oai_dc.xsd http://www.openarchives.org/OAI/2.0/oai_dc/ olac http://www.language-archives.org/OLAC/olac-0.2.xsd http://www.language-archives.org/OLAC/0.2/ perseus http://www.perseus.tufts.edu/persmeta.xsd http://www.perseus.tufts.edu/persmeta.dtd

Request

List the metadata formats that can be disseminated from the repository http://memory.loc.gov/cgi-bin/oai.

http://memory.loc.gov/cgi-bin/oai? verb=ListMetadataFormats

Response

The response shows that the repository supports two metadata formats: oai_dc, and oai_marc. For each of the formats, the location of an XML Schema describing the format is given. The support of these formats at the repository-level does not imply support of each format for each item of the repository.

2002-06-08T15:19:13Z http://memory.loc.gov/cgi-bin/oai oai_dc http://www.openarchives.org/OAI/2.0/oai_dc.xsd http://www.openarchives.org/OAI/2.0/oai_dc/ oai_marc http://www.openarchives.org/OAI/1.1/oai_marc.xsd http://www.openarchives.org/OAI/1.1/oai_marc

Request

List the metadata formats that can be disseminated for the unique identifier oai:lcoa1.loc.gov:loc.rbc/rbpe.00000111 in the repository http://memory.loc.gov/cgi-bin/oai. The identifier, however, does not exist and therefore, the response contains an error element and no metadataFormat container. [URL shown without encodingfor better readability].

http://memory.loc.gov/cgi-bin/oai? verb=ListMetadataFormats&identifier=oai:lcoa1.loc.gov:loc.rbc/rbpe.00000111

Response

2002-06-08T15:19:13Z http://memory.loc.gov/cgi-bin/oai oai:lcoa1.loc.gov:loc.rbc/rbpe.00000111 has the structure of a valid LOC identifier, but it maps to no known item

4.5 ListRecords

Summary and Usage Notes

This verb is used to harvest records from a repository. Optional arguments permit selective harvesting of records based on set membership and/or datestamp. Depending on the repository's support for deletions, a returned header may have a status attribute of "deleted" if a record matching the arguments specified in the request has been deleted. No metadata will be present for records with deleted status.

Arguments

• **from** an optional argument with a UTCdatetime value, which specifies a lower bound for datestamp-based selective harvesting.
• **until** an optional argument with a UTCdatetime value, which specifies a upper bound for datestamp-based selective harvesting.
• **set** an optional argument with a setSpec value , which specifies set criteria for selective harvesting.
• **resumptionToken** an exclusive argument with a value that is the flow control token returned by a previous ListRecords request that issued an incomplete list.
• **metadataPrefix** a required argument (unless the exclusive argument resumptionToken is used) that specifies the metadataPrefix of the format that should be included in the metadata part of the returned records. Records should be included only for items from which the metadata format
  matching the metadataPrefix can be disseminated. The metadata formats supported by a repository and for a particular item can be retrieved using the [ListMetadataFormats](#ListMetadataFormats) request.

Error and Exception Conditions

• **badArgument** - The request includes illegal arguments or is missing required arguments.
• **badResumptionToken** - The value of the resumptionToken argument is invalid or expired.
• **cannotDisseminateFormat** - The value of the metadataPrefix argument is not supported by the repository.
• **noRecordsMatch** - The combination of the values of the from, until, set and metadataPrefix arguments results in an empty list.
• **noSetHierarchy** - The repository does not support sets.

Examples

Request

List the records expressed in oai_rfc1807 metadata format, that have been added or modified since January 15, 1998 in the hepsubset of the physics set [URL shown without encoding for better readability].

http://an.oa.org/OAI-script? verb=ListRecords&from=1998-01-15&set=physics:hep&metadataPrefix=oai_rfc1807

Response

Two records are returned:

• The first record is expressed in the oai_rfc1807 metadata. This record also has an about part, and the item from which it was disseminated belongs to two sets (physics:hep and math).
• The second has a header with a status="deleted" attribute (and therefore no metadata part).

Note: The reply only includes records for those items from which metadata in oai_rfc1807 can be disseminated. No records are returned for those items that fit the from, until, and set arguments but from which the specified format can not be disseminated.

2002-06-01T19:20:30Z http://an.oa.org/OAI-script

Request

Request records in the oai_dc metadata format, modified or added between 2:15pm and 2:20pm UTC on May 1st 2002. [URL shown without encoding for better readability].

http://www.perseus.tufts.edu/cgi-b:in/pdataprov? verb=ListRecords&from=2002-05-01T14:15:00Z&until=2002-05-01T14:20:00Z& metadataPrefix=oai_dc

Response

Two records are returned. The second one has a provenancecontainer in its about element, giving an insight in its chain of provenance.

2002-06-01T19:20:30Z http://www.perseus.tufts.edu/cgi-bin/pdataprov

Request

Request records in the the oai_marc metadata format, modified or added between 2:00am and 3:00am UTC on June 1st 2002. The specified granularity is not supported by the repository and therefore, an error with code attribute of badArgumentis returned. [URL shown without encoding for better readability].

http://memory.loc.gov/cgi-bin/oai? verb=ListRecords&from=2002-06-01T02:00:00Z&until=2002-06-01T03:00:00Z&metadataPrefix=oai_marc

Response

2002-06-01T19:20:30Z http://memory.loc.gov/cgi-bin/oai

4.6 ListSets

Summary and Usage Notes

This verb is used to retrieve the set structure of a repository, useful for selective harvesting.

Arguments

• resumptionToken an exclusive argument with a value that is the flow control token returned by a previous ListSets request that issued an incomplete list.

Error and Exception Conditions

• **badArgument** - The request includes illegal arguments or is missing required arguments.
• **badResumptionToken** - The value of the resumptionToken argument is invalid or expired.
• **noSetHierarchy** - The repository does not support sets.

Examples

Request

http://an.oa.org/OAI-script? verb=ListSets

Response

The following response indicates a set hierarchy with two top level sets with respective setSpec music and video. The music set has two subsets, with setSpec music:(muzak) and music:(elec). The subsets identified by setSpec music:(elec), has a setDescription element which holds a Dublin Core container, used to describe its contents.

2002-08-11T07:21:33Z http://an.oa.org/OAI-script music Music collection music:(muzak) Muzak collection music:(elec) Electronic Music Collection <oai_dc:dc xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ " title="undefined" rel="noopener noreferrer">http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> dc:descriptionThis set contains metadata describing electronic music recordings made during the 1950ies video Video Collection

Request

http://purl.org/alcme/etdcat/servlet/OAIHandler? verb=ListSets

Response

The response shows that the repository does not have a set hierarchy.

2001-06-01T19:20:30Z http://purl.org/alcme/etdcat/servlet/OAIHandler This repository does not support sets

5. Dublin Core

The following table shows the XML Schema for Dublin Core without qualification, which is associated with the reserved metadataPrefix oai_dc in the OAI-PMH. All examples in this document that include Dublin Core metadata, validate against this XML schema. Schema for other metadata formats are provided in the accompanying Implementation Guidelines document.

Examples

<oai_dc:dc xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ " title="undefined" rel="noopener noreferrer">http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> <dc:title xml:lang="en">The Cornell Law Quarterly dc:date1915-1916 dc:identifierhttp://heinonline.org/HeinOnline/show.pl? handle=hein.journals/clqv1%26id=1%26size=4 dc:rightsAvailable by Subscription. See http://www.wshein.com

<oai_dc:dc xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ " title="undefined" rel="noopener noreferrer">http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> <dc:title xml:lang="en">Grassmann's space analysis dc:creatorHyde, E. W. (Edward Wyllys) dc:subjectLCSH:Ausdehnungslehre; LCCN QA205.H99 dc:publisherJ. Wiley & Sons dc:dateCreated: 1906; Available: 1991 dc:typetext dc:identifierhttp://resolver.library.cornell.edu/math/1796949 dc:languageenglish <dc:rights xml:lang="en">Public Domain

6. Implementation Guidelines

Some passages in this document refer to the existence and goals of the accompanying Implementation Guidelines document.

Acknowledgements

Support for the development of the OAI-PMH and for other Open Archives Initiative activities comes from the Digital Library Federation, the Coalition for Networked Information, and from the National Science Foundation through Grant No. IIS-9817416.

This document is based on the deliberations of the OAI Technical Committee: Caroline Arms (Library of Congress), Thomas Baron (CERN), Steven Bird (University of Pennsylvania), Les Carr (University of Southampton), Tim Cole (University of Illinois at Urbana Champaign), Thomas Krichel (Long Island University), Carl Lagoze (Cornell University), Michael Nelson (NASA), Andy Powell (UKOLN & University of Bath), Mogens Sandfaer (Danmarks Tekniske Videncenter), Hussein Suleman (Virginia Tech), Robert Tansley (HP), Herbert Van de Sompel (Los Alamos National Laboratory), Simeon Warner (Cornell University), Muhammad Zubair (Old Dominion University) and Jeff Young (OCLC).

Many thanks to all involved in alpha-testing of version 2.0 of the OAI-PMH. In addition to the above: Tim Brody (University of Southampton), Irena Dijour (Ex Libris), Naomi Dushay (Cornell University), Susanne Dobratz (Humboldt Universität zu Berlin), Curtis Fornadley (UCLA), Christopher Gutteridge (University of Southampton), Alan Kent (InQuirion Pty Ltd & RMIT University), David Letts (The British Library), Xiaoming Liu (Old Dominion University), Jon Phipps (Cornell University) and Francois Schiettecatte (FS Consulting Inc).

Special thanks to Pete Johnston (UKOLN & University of Bath) and Andy Powell (UKOLN & University of Bath) for work on the Dublin Core schema, and to Donna Bergmark (Cornell University) for work on the OAI validation and registration service.

Many thanks to everyoneinvolved in the compilation and alpha-testing of version 1.0 and 1.1 of the OAI-PMH, and to all of you using this protocol.

Document History

2015-01-08: Add explicit CC BY-SA license, HTML fixes. No change to protocol.
2008-12-07: Fix links to previous versions.
2008-12-02: Spell checked after all these years and several errors corrected. No change of meaning. Added links to previous versions.
2004-10-12: Changed wording and schema definition for characters allowed in setSpec and metadataPrefix to agree.
2004-09-15: Added section 2.5.1. Corrected section 2.6. Corrected second example in section 5. Changed schema to defined a type for protocolVersion and to enforce use of Z notation for UTC datetime.
2003-02-21: Changed identifiers in the examples so that they conform to version 2.0 of the oai-identifier specification.
2002-12-19: Updated oai_dc schema to use revised Dublin Core schema simpledc20021212.xsd. Corrected provenance blocks in examples (sections 2.5 and 4.5).
2002-06-14: Release of OAI-PMH version 2.0.
2002-05-02: Release of beta version of OAI-PMH version 2.0.
2002-05-06: Release of alpha-4 version of OAI-PMH version 2.0. Changed document to reflect association of datestamps and deleted status with records as opposed to items. Changed requestURL to request. Changed schema location of oai-identifier and oai_dc schema. Changed validation of about, metadata, description and setDescription to strict.
2002-04-07: Changed document to reflect the usage of a single schema to validate all OAI-PMH responses.
2002-03-30: Release of alpha two version of OAI-PMH version 2.0.
2002-03-01: Release of alpha version of OAI-PMH version 2.0