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Document Availability Information API (DAIA)

Jakob Voß (VZG)

Uwe Reh (Hebis)

2015-04-22 (version 0.9.0)

Table of Contents

1 Introduction

The Document Availability Information API (DAIA) defines model of document availability, a set of exchangeable serializations of this model (in JSON and XML), and an HTTP API to query document availability information encoded in any of these serializations. The DAIA data model basically consists of abstract documents, concrete holdings of documents, and document services, with an availability status.

Information expressed by DAIA can also be encoded in RDF as described with the DAIA Ontology

1.1 Status of this document

This document is a draft of what is going to be DAIA 1.0 specification. Version 0.5 is available at

All documentation and schemas are generated from the source file written in Pandoc’s Markdown and converted with makespec.

Updates and sources of DAIA 1.0 can be found at The current version of this document was last modified at 2015-04-22 with revision b1605dd.

This document is publically available under the terms of the Creative-Commons Attribution-ShareAlike Derivative (CC-BY-SA 3.0) license. Feedback is welcome:

1.2 Conformance requirements

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.

1.3 Namespaces

DAIA serializations in XML (DAIA/XML) is formally described by an XML schema. The DAIA/XML Schema is identified by the XML namespace The XML namespace prefix daia is recommeded..

The current XML Schema is located at

2 Structure and Encoding

In the following paragraphs we want to give a short introduction to DAIA format. Examples of equivalent DAIA response fragments are given in DAIA/JSON and DAIA/XML. The basic information entities of DAIA format are:

Daia entities in DAIA/JSON are encoded as simple nodes with child nodes, daia entities in DAIA/XML are encoded as XML-elements with attributes and child-elements. XML elements include namespaces so you must use an XML parser with support of namespaces to process DAIA/XML. Below the possible and mandatory attributes and child elements or nodes of each daia entities are defined. If an entity is marked with a question mark (?) it is optional. If an entity is marked with a star (\*) it is repeatable and optional. All other entities are mandatory and non-repeatable. Repeatable elements in DAIA/XML are just line up after another. Repeatable elements in DAIA/JSON must be encoded as array with one ore more content elements.

The order or repeatable elements (message, limitation, document, item, available, unavailable) is irrelevant. DAIA servers and clients MAY sort these lists as they like.



 "item": [ { ... }, { ... }, ... ]
<item ...> ... </item>
<item ...> ... </item>

not repeated

 "item": [ { ... } ]
<item ...> ... </item>

Content of entities that must not have child nodes are encoded as Unicode strings, numbers, or boolean values. Unless a more specific limitation is defined with an XML Schema Datatype, the content must be an Unicode string (but it may be the empty string). DAIA uses the following XML Schema Datatypes:

2.1 Root element

A DAIA response in DAIA/XML and DAIA/JSON contains exactely one root element.

In DAIA/XML the root element name is daia. The XML namespace MUST be specified and the XML Schema MAY be referred to. In DAIA/JSON, the fixed child element schema with value MAY be used to refer to DAIA specification and namespace.

  • version (attribute) - the daia version number (currently 0.5)
  • timestamp (attribute) - the time the document was generated. Type xsd:dateTime.
  • message* (element) - (error) message(s) about the whole response
  • institution? (element) - information about the institution that grants or knows about services and their availability
  • document* (element) - a group of items that can be refered to with one identifier. Please note that although the number of document elements can be zero or greater one, one single document entry should be considered as the default.
  "version" : "0.5",
  "schema" : "",
  "timestamp" : "2009-06-09T15:39:52.831+02:00",
  "institution" : { }
<daia xmlns="" version="0.5"

Equivalent DAIA/XML with different namespace prefix:

<d:daia xmlns:d="" version="0.5"

2.2 Document element

The document element describes a single document. Nevertheless, several instances of a document (e.g. copies of a book) can exist. For these instances, have a look at the item element below.

  • id (attribute) - each document needs an unique id to query it (e.g. ISBN, ppn, etc.). Please consider that ids have to be URIs. Type xsd:anyURI.
  • href? (attribute) - a link to the document or to additional information. Type xsd:anyURI.
  • message* (element) - (error) message(s) about the document.
  • item* (element) - an instance or copy of the queried document (correspondends to the FRBR class of same name).
  "document" : [ {
    "href" : "",
    "id" : "gvk:ppn:57793371X",
    "item" : [ {  }, {  }, {  } ]
  } ]
<document href="" 

2.3 Item element

The item node references a single instance (copy, URI, etc.) of a document. The availability information is of course connected to the item nodes.

  • id? (attribute) - again, each item (instance) may have an unique ID (e.g., an individual call number for a book). Please consider that ids have to be URIs. Type xsd:anyURI.
  • href? (attribute) - a link to the item or to additional information. Type xsd:anyURI.
  • part? (attribute) - indicate that the item only contains a part of the document (part="narrower") or contains more than the document (part="broader")
  • message* (element) - (error) message(s) about the item.
  • label? (element) - a label that helps to identify and/or find the item (call number etc.)
  • department? (element) - an administrative sub-entitity of the institution that is responsible for this item
  • storage? (element) - a physical location of the item (stacks, floor etc.)
  • available* (element) - information about an available service with the item.
  • unavailable* (element) - information about an unavailable service with the item

Multiple service status can be given for an item represented by different available/unavailable elements.

    "item" : [ {
      "id" : "id:123",
      "message" : [ { "lang": "en", "content": "foo" } ],
      "department" : { "id": "id:abc" },
      "label" : "bar",
      "available" : [ {"service" : "presentation"}, 
                      {"service" : "loan"}, 
                      {"service" : "interloan"} ],
      "unavailable" : [ {"service" : "openaccess"} ]
    } ]
<item id="id:123">
   <message lang="en">foo</message>
   <department id="id:abc" />
   <available service="presentation" />
   <available service="loan" />
   <available service="interloan" />
   <unavailable service="openaccess" />

Partial items refer to items which contain less (narrower) or more (broader) than the whole document:

narrower in DAIA/XML

<document id="x:123">
  <item id="x:ABC" part="narrower"/>

narrower in DAIA/RDF

<x:123> a bibo:Document ; holding:narrowerExemplar <x:ABC> .
<x:123> a bibo:Document ; dct:hasPart [ holding:exemplar <x:ABC> ] } .

broader in DAIA/XML

<document id="x:123">
  <item id="x:ABC" part="broader"/>

broader in DAIA/RDF

<x:123> a bibo:Document ; holding:broaderExemplar <x:ABC> .
<x:123> a bibo:Document ; holding:exemplar [ dct:hasPart <x:ABC> ] } .

2.4 Available element

  • service? (attribute) - the specific service from the Document Service Ontology (DSO). The value can be given as full URI or as simple name. A name is mapped to an URI by uppercasing the first letter and prepending the base URI Multiple services are represented by multiple available/unavailable elements. Type enumeration or xsd:anyURI.
  • href? (attribute) - a link to perform, register or reserve the service. Type xsd:anyURI.
  • delay? (attribute) - a time period of estimated delay. Use unknown or an ISO time period. If missing, then there is probably no significant delay. Type xsd:duration or the string unknown.
  • message* (element) - (error) message(s) about the specific availability status of the item.
  • limitation* (element) - more specific limitations of the availability status.

Typical DSO Services used in DAIA

presentation :  The item is accessible within the institution (in their rooms, in their intranet etc.).

loan :
The item is accessible outside of the institution (by lending or online access) for a limited time.

openaccess :
The item is accessible freely without any restrictions by the institution (Open Access or free copies).

interloan :
The item is accessible mediated by another institution.

unspecified :
The item is accessible for an unspecified purpose by an unspecified way.

One MAY use custom service types, not specified in DSO, if these services are specified with an URI as subclasses of [dso:DocumentService].

If you omit the service element then the unspecified service must be assumed (do not use the string unspecified or the empty string but just omit to specify a service).

  "available": [ { "service":"loan", "delay":"PT2H" 
<available service="loan" delay="PT2H" />

2.5 Unavailable element

The content of an unavailable element is identical to the structure of the available element in most cases.

  • service? (attribute) - see above
  • href? (attribute) - see above
  • expected (attribute) - A time period until the service will be available again. Use unknown or an ISO time period. If missing, then the service probably won’t be available in the future. Type xsd:date or xsd:dateTime or the string unknown.
  • message* (element) - see above
  • limitation* (element) - more specific limitations of the availability status
  • queue? (attribute) - the number of waiting requests for this service. Type xsd:nonNegativeInteger.

If no expected element is given, it is not sure whether the item will ever be available, so this is not the same as setting it to unknown. If no queue element is given, it may (but does not need to) be assumed as zero.

    "unavailable": [ {
    } ]
<unavailable service="presentation" delay="PT4H" />

2.6 Messages

Messages can occur at several places in a DAIA response. Messages are not meant to be shown to end-users, but only used for debugging. If you need a DAIA message to transport some relevant information, you likely try to use DAIA for the wrong purpose.

  • lang (attribute) - a RFC 3066 language code. Type xsd:language.
  • content (string) - the message text, a simple string without further formatting. If content is an empty string, the content element/attribute SHOULD be omitted.
  • errno? (attribute) - an error code (integer value). Type xsd:integer.

In DAIA/XML the message element is a repeatable XML element with optional attributes lang and errno and the string encoded as element content. In DAIA/JSON a message element is an object with lang, errno, and string as keys. Multiple messages are combined in a JSON array:

  "message" : [ {
    "content":"request failed",
  } ]
<message lang="en">request failed</message>

2.7 Additional entities

In this section, the additional entries institution, department, storage and limitation are discussed.

The content of these nodes is identical and discussed below.

  • id? - a (persistent) identifier for the entity. Type xsd:anyURI.
  • href? - a URI linking to the entity. Type xsd:anyURI.
  • content? - a simple message text describing the entity.

If content is an empty string, it should be removed in DAIA encodings. Applications may treat a missing content as the empty string. It is recommended to supply an id property to point to a taxonomy or authority record and a href property to provide a hyperlink to information about the specified entity.

TODO: multilingual content

    "institution" : { "href" : "" }
    "department" : { 
                     "id" : "info:isil/DE-7-022",
                     "content" : "Library of the Geographical Institute, Goettingen University"
    "limitation"  : { "content" : "3 day loan" }
<institution href=""/>
<department id="info:isil/DE-7-022">Library of the Geographical Institute, Goettingen University</department> 
<limitation>3 day loan</limitation>

3 Query API

A DAIA-API is provided in form of a Base URL that can be queried by HTTP (or HTTPS) GET. The Base URL may contain fixed query parameters but it must not contain the query parameters id and format. A DAIA query is constructed of the Base URL and a query parameter id for the document URI to be queried for and format with one of xml and json. The value of the format parameter is case insensitive. The response muste be a DAIA/XML document for format=xml and a DAIA/JSON document for format=json. If no format parameter is given or if the parameter value is no known value, a DAIA/XML document may be returned, but you can also return other formats. In particular a DAIA-API may return DAIA/RDF in RDF/XML for format=rdfxml and DAIA/RDF in Turtle for format=ttl. The HTTP response code must be 200 for all non-empty responses (DAIA/JSON and DAIA/XML) and 404 for empty responses (for instance RDF/XML in Turtle format). Multiple document URIs can be provided by concatenating them with the vertical bar (|, %7C in URL-Encoding) but a DAIA server may limit queries to any positive number of URIs.

A DAIA server SHOULD include the HTTP response header Content-Language to indicate the language of textual response fields. The HTTP request header Accept-Language SHOULD be respected to select between multiple languages.


Base URL Document URIs Format Query URL gvk:ppn:588923168 DAIA/XML gvk:ppn:588923168 DAIA/JSON gvk:ppn:588923168 and gvk:ppn:365058963 DAIA/JSON

4 References

5 Appendixes

The following appendixes are informative only.

5.1 DAIA Simple

DAIA Simple is a boiled down version of a DAIA response consisting of plain key-value structure having the following fields:

most relevant service (openaccess, loan, presentation, none)
boolean value (true or false)
optional field only allowed if available=true. Allowed values must conform to xsd:duration or the string unknown.
Only if available=false. Allowed values must conform to xsd:date or xsd:dateTime or the string unknown.
length of waiting queue (only if available=false)
optional URL to perform or request a service.
optional string or boolean value describing an additional limitation.

To give a few examples, encoded in JSON:

{ "service": "loan", "available": true }
{ "service": "loan", "available": false, "expected": "2014-12-07" }
{ "service": "presentation", "available": true }
{ "service": "openaccess", "available": true,
  "href": "" }

Note that DAIA Simple only covers one typical use case but it may not suitable for other applications.

5.2 Notes

5.3 Revision history