% Patrons Account Information API (PAIA) % Jakob Voß % GIT_REVISION_DATE
The Patrons Account Information API (PAIA) is a HTTP based programming interface to access library patron information, such as loans, reservations, and fees. Its primary goal is to provide patron access for discovery interfaces and other third-party applications to integrated library system, as easy as possible.
The specification has been created collaboratively based on use cases and taking into account existing related standards and products such as NISO Circulation Interchange Protocol (NCIP), [X]SLNP, DLF-ILS recommendations, and VuFind ILS drivers among others.
Updates and sources can be found at http://github.com/gbv/paia. The current version of this document was last modified at GIT_REVISION_DATE with revision GIT_REVISION_HASH.
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.
A PAIA server MUST implement PAIA core and it MAY implement PAIA auth. If PAIA auth is not implemented, another way SHOULD BE documented to distribute patron identifiers and access tokens. A PAIA server MAY support only a subset of methods but it MUST return a valid response or error response on every method request, as defined in this document.
PAIA consists of two independent parts:
-
PAIA core defines six basic methods to look up loaned and reserved items, to request and cancel loans and reservations, and to look up fees and general patron information.
-
PAIA auth defines three authentification methods (login, logout, and password change) to get access tokens, required by PAIA core.
Each method is accessed at an URL with a common base URL for PAIA core methods and common base URL for PAIA auth methods. A server SHOULD NOT provide additional methods at these base URLs and it MUST NOT propagate additional methods at these base URLs as belonging to PAIA.
In the following, the base URL https://example.org/core/ is used for PAIA core and https://example.org/auth/ for PAIA auth.
Authentification in PAIA is based on OAuth 2.0 (RFC 6749) with bearer tokens (RFC 6750) over HTTPS (RFC 2818). For security reasons, PAIA methods MUST be requested via HTTPS only. A PAIA client MUST NOT ignore SSL certificate errors; otherwise access token (PAIA core) or even password (PAIA auth) are compromised by the client.
Each PAIA method is identified by an URL and a HTTP verb (either HTTP GET or
HTTP POST). For POST methods a request body MUST be included in JSON format
(Content-Type: application/json or application/json; charset=utf-8). A PAIA
auth server MAY additionally accept URL-encoded HTTP POST request bodies with
content type application/x-www-form-urlencoded.
In addition there is the special request parameter access_token for an
access token, which can be sent either as HTTP
query parameter or in a HTTP request header.
The HTTP response content type of a PAIA response is a JSON object (HTTP header
Content-Type: application/json; charset=utf-8), optionally wrapped as JSONP
(HTTP header Content-Type: application/javascript; charset=utf-8).
Every request parameter and every response field is defined with
- the name of the parameter/field
- the ocurrence (occ) of the parameter/field being one of
0..1(optional, non repeatable)1..1(mandatory, non repeatable)1..n(mandatory, repeatbale)0..n(optional, repeatable)
- the data type of the parameter/field.
- a short description
Simple parameter names and response fields consist of lowercase letters a-z only.
Repeatable response fields are encoded as JSON arrays, for instance:
{ "fee" : [ { ... }, { ... } ] }
Hierarchical JSON structures in this document are refereced with a dot (.)
as separator. For instance the subfield/parameter item of the doc element
is referenced as doc.item and refers to the following JSON structure:
{ "doc" : [ { "item" : "..." } ] }
The following special request parameters can be added to any request as URL query parameters:
callback
: A JavaScript callback method name to return JSONP instead of JSON. The
callback SHOULD only contain alphanumeric characters and underscores;
any invalid characters MUST be stripped by a PAIA server. If callback
is given, the response content type MUST be application/javascript.
suppress_response_codes
: If this parameter is present, all responses MUST be returned with a
200 OK status code, even error responses.
All PAIA methods, with login from PAIA auth as only exception,
require an access token as special request parameter. The access token is a
so called bearer token as described in RFC 6750. The access token can be send
either as URL query parameter or in a HTTP header. For instance the following
requests both get information about patron 123 with access token
vF9dft4qmT:
curl -H "Authorization: Bearer vF9dft4qmT" https://example.org/core/patron/123
curl -H https://example.org/core/patron/123?access_token=vF9dft4qmT
An access token is valid for a limited set of actions, referred to as scope. The following scopes are possible for PAIA core:
read_patron : Get patron information by the patron method. read_fees : Get fees of a patron by the fees method. read_items : Get a patron’s item information by the items method. write_items : Request, renew, and cancel items by the request, renew, and cancel methods.
For instance a particular token with scopes read_patron and read_items may
be used to for read-only access to information about a patron, including its
loans and requested items but not its fees.
A PAIA server SHOULD send the following HTTP headers with every response:
X-OAuth-Scopes : A space-separated list of scopes, the current token has authorized X-Accepted-OAuth-Scopes : A space-separated list of scopes, the current method checks for
For PAIA auth an additional scope is possible:
change_password : Change the password of a patron with PAIA auth change method.
A PAIA core server SHOULD NOT include the change_password scope in the
X-OAuth-Scopes header because the scope is limited to PAIA auth. A PAIA auth
server MAY send X-OAuth-Scopes and X-Accepted-OAuth-Scopes headers with
both PAIA auth scopes and PAIA core scopes.
Two classes of errors must be distinguished:
Document errors
: Unknown document URIs and failed attempts to request, renew, or cancel
a document do not result in an error response. Instead they are
indicated by the doc.error response field.
Request errors
: Malformed requests, failed authentification, unsupported methods, and
unexpected server errors such as backend downtime etc. MUST result in an
error response. An error response is returned with a HTTP status code
4xx (client error) or 5xx (server error) as defined in RFC 2616, unless
the request parameter suppress_response_codes is given.
The response body of a request error is a JSON object with the following fields (compatible with OAuth error response):
name occ data type description
error 1..1 string alphanumerical error code code 0..1 nonnegative integer HTTP status error code error_description 0..1 string Human-readable error description error_uri 0..1 string Human-readable web page about the error
The code field is REQUIRED with request parameter suppress_response_codes
in PAIA core. It SHOULD be omitted with PAIA auth requests to not confuse OAuth
clients.
The following error responses are expected:1
error code description
not_found 404 Unknown request URL or unknown patron. Implementations SHOULD
first check authentification and prefer error invalid_grant or
access_denied to prevent leaking patron identifiers.
not_implemented 501 Known but unspupported request URL (for instance a PAIA auth server
server may not implement http://example.org/core/change)
invalid_request 405 Unexpected HTTP verb (all but GET, POST, HEAD)
invalid_request 400 Malformed request (for instance error parsing JSON, unsupported request content type, etc.)
invalid_request 422 The request parameters could be parsed but they don’t match to the request method (for instance missing fields, invalid values, etc.)
invalid_grant 401 The access token was missing, invalid, or expired
insufficient_scope 403 The access token was accepted but it lacks permission for the request
access_denied 403 Wrong or missing credentials to get an access token
internal_error 500 An unexpected error ocurred. This error corresponds to a bug in the implementation of a PAIA auth/core server
service_unavailable 503 The request couldn’t be serviced because of a temporary failure
bad_gateway 502 The request couldn’t be serviced because of a backend failure (for instance the library system’s database)
gateway_timeout 504 The request couldn’t be serviced because of a backend failure
For instance the following response could result from a request with malformed URIs
{
"error": "invalid_request",
"code": "422",
"error_description": "malformed item identifier provided: must be an URI",
"error_uri": "http://example.org/help/api"
}
The following data types are used to define request and response format:
string
: A Unicode string. Strings MAY be empty.
nonnegative integer
: An integer number larger than or equal to zero.
boolean
: Either true or false. Note that omitted boolean values are not false by
default but unknown!
date
: A date value in YYYY-MM-DD format.
money
: A monetary value with currency (format [0-9]+\.[0-9][0-9] [A-Z][A-Z][A-Z]),
for instance 0.80 USD.
email
: syntactically correct email address.
URI
: syntactically correct URI.
account state
: A nonnegative integer representing the current state of a patron account. Possible
values are:
0. active
1. inactive
2. inactive because account expired
3. inactive because of outstanding fees
4. inactive because account expired and outstanding fees
A PAIA server MAY define additional states which can be mapped to `1` by PAIA
clients. In JSON account states MUST be encoded as numbers instead of strings.
document status : A nonegative integer representing the current relation between a particular document and a particular patron. Possible values are:
0. no relation (this applies to most combinations of document and patron, and
it can be expected if no other state is given)
1. reserved (the document is not accesible for the user yet, but it will be)
2. ordered (the document is beeing made accesible for the user)
3. held (the document is on loan by the patron)
4. provided (the document is ready to be used by the patron)
5. rejected
A PAIA server MUST NOT define any other document states. In JSON document status
MUST be encoded as numbers instead of strings.
document : A key-value structure with the following fields
name occ data type description
----------- ------ --------------------- ----------------------------------------------------------
status 1..1 document status status (0, 1, 2, 3, 4, or 5)
item 0..1 URI URI of a particular copy
edition 0..1 URI URI of a the document (no particular copy)
requested 0..1 URI URI that was originally requested
about 0..1 string textual description of the document
label 0..1 string call number, shelf mark or similar item label
queue 0..1 nonnegative integer number of waiting requests for the document or item
renewals 0..1 nonnegative integer number of times the document has been renewed
reminder 0..1 nonnegative integer number of times the patron has been reminded
duedate 0..1 date date of expiry of the document statue (most times loan)
cancancel 0..1 boolean whether an ordered or provided document can be canceled
canrenew 0..1 boolean whether a document can be renewed
error 0..1 string error message, for instance if a request was rejected
storage 0..1 string location of the document
storageid 0..1 URI location URI
----------- ------ --------------------- ----------------------------------------------------------
For each document at least an item URI or an edition URI MUST be given. The
response fields `label`, `storage`, `storageid`, and `queue`
correspond to properties in DAIA.
An example of a document (with status 5=rejected) serialized in JSON is
given below. In this case an arbitrary copy of a selected document was
requested and mapped to a particular copy that turned out to be not accesible:
~~~~ {.json}
{
"status": 5,
"item": "http://example.org/items/barcode1234567",
"edition": "http://example.org/documents/9876543",
"requested": "http://example.org/documents/9876543",
"error": "sorry, we found out that our copy is lost!"
}
~~~~
Each API method of PAIA core is accessed at an URL that includes the URI-escaped patron identifier.
purpose : Get general information about a patron HTTP verb and URL : GET https://example.org/core/**{uri_escaped_patron_identifier}** scope : read_patron response fields : name occ data type description --------- ------ --------------- ------------------------------ name 1..1 string full name of the patron email 0..1 email email address of the patron expires 0..1 date date of patron account expiry status 0..1 account state current state (0, 1, 2, or 3) --------- ------ --------------- -------------------------------
Additional field such as address may be added in a later revision.
Example
GET /core/patron/123 HTTP/1.1
Host: example.org
Accept: application/json
Authorization: Bearer a0dedc54bbfae4b
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
X-Accepted-OAuth-Scopes: read_patron
X-OAuth-Scopes: read_patron, read_fees, read_items, write_items
{
"name": "Jane Q. Public",
"email": "jane@example.org",
"expires": "2013-05-18",
"status": 0
}
purpose : Get a list of loans, reservations and other items related to a patron HTTP verb and URL : GET https://example.org/core/**{uri_escaped_patron_identifier}**/items scope : read_item response fields : name occ data type description ------ ------ ----------- ----------------------------------------- doc 0..n document list of documents (order is irrelevant) ------ ------ ----------- -----------------------------------------
In most cases, each document will have an item URI for a particular copy, but users may also have requested an edition.
purpose : renew one or more documents held by the patron HTTP verb and URL : POST https://example.org/core/**{uri_escaped_patron_identifier}**/renew scope : write_item request parameters : ------------- ------ -------- ------------------------------ doc 1..n list of documents to renew doc.item 0..1 URI URI of a particular item doc.edition 0..1 URI URI of a particular edition ------------- ------ -------- ----------------------------- response fields : name occ data type description ------ ------ ----------- ----------------------------------------- doc 1..n document list of documents (order is irrelevant) ----- ------ ------------ -----------------------------------------
purpose : Request one or more items for reservation or delivery. HTTP verb and URL : POST https://example.org/core/**{uri_escaped_patron_identifier}**/request scope : write_item request parameters : name occ data type description --------------- ------ ----------- ------------------------------ doc 1..n list of documents to renew doc.item 0..1 URI URI of a particular item doc.edition 0..1 URI URI of a particular edition doc.storage 0..1 string Requested pickup location doc.storageid 0..1 URI Requested pickup location --------------- ------ ----------- ------------------------------ response fields : name occ data type description ------ ------ ----------- ----------------------------------------- doc 1..n document list of documents (order is irrelevant) ------ ------ ----------- -----------------------------------------
purpose : Cancel requests for items. HTTP verb and URL : POST https://example.org/core/**{uri_escaped_patron_identifier}**/cancel scope : write_item request parameters : name occ data type ------------- ------ ----------- ----------------------------- doc 1..n list of documents to renew doc.item 0..1 URI URI of a particular item doc.edition 0..1 URI URI of a particular edition ------------- ------ ----------- ----------------------------- response fields : name occ data type description ------ ------ ----------- ----------------------------------------- doc 1..n document list of documents (order is irrelevant) ------ ------ ----------- -----------------------------------------
purpose : Look up current fees of a patron. HTTP verb and URL : GET https://example.org/core/**{uri_escaped_patron_identifier}**/fees scope : read_fees response fields : name occ data type description ------------- ------ ----------- ---------------------------------------- amount 0..1 money Sum of all fees. May also be negative! fee 0..n list of fees fee.amount 1..1 money amout of a single fee fee.date 0..1 date date when the fee was claimed fee.about 0..1 string textual information about the fee fee.item 0..1 URI item that caused the fee fee.edition 0..1 URI edition that caused the fee ------------- ------ ----------- ----------------------------------------
PAIA auth defines three methods for authentification based on username and password. These methods can be used to get access tokens and patron identifiers, which are required to access PAIA core methods. There MAY be additional or alternative ways to distribute and manage access tokens and patron identifiers.
There is no strict one-to-one relationship between username/password and patron identifier/access token, but a username SHOULD uniquely identify a patron identifier. A username MAY even be equal to a patron identifier, but this is NOT RECOMMENDED. An access token MUST NOT be equal to the password of the same user.
A PAIA auth server acts as OAuth authorization server (RFC 6749) with password credentials grant, as defined in section 4.3 of the OAuth 2.0 specification. The access tokens provided by the server are so called OAuth 2.0 bearer tokens (RFC 6750).
A PAIA auth server MUST protect against brute force attacks (e.g. using rate-limitation or generating alerts). It is RECOMMENDED to further restrict access to PAIA auth to specific clients, for instance by additional authorization.
The login method is the only PAIA method that does not require an access
token as part of the query.
purpose : Get a patron identifier and access token to access patron information URL : https://example.org/auth/**login** request parameters : name occ data type ------------ ------ ----------- -------------------------------- username 1..1 string User name of a patron password 1..1 string Password of a patron grant_type 1..1 string Fixed value set to "password" scope 0..1 string Space separated list of scopes ------------ ------ ----------- --------------------------------
If no scope parameter is given, it is set to the default value read_patron read_fees read_items write_items for full access to all PAIA core methods (see
access tokens and scopes ).
The response format is a JSON structure as defined in section 5.1 (successful response) and section 5.2 (error response) of OAuth 2.0. The PAIA auth server may grant different scopes than requested for, for instance if the account of a patron has expired, so the patron should not be allowed to request and renew new documents.
response fields : name occ data type description -------------- ------ --------------------- ------------------------------------------------- patron 1..1 string Patron identifier access_token 1..1 string The access token issued by the PAIA auth server token_type 1..1 string Fixed value set to "Bearer" scope 1..1 string Space separated list of granted scopes expires_in 0..1 nonnegative integer The lifetime in seconds of the access token -------------- ------ --------------------- -------------------------------------------------
Example of a successful request
POST /auth/login
Host: example.org
Accept: application/json
Content-Type: application/json
Content-Length: 85
{
"username": "alice02",
"password": "jo-!97kdl+tt",
"grant_type": "password"
}
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Cache-Control: no-store
Pragma: no-cache
{
"access_token": "2YotnFZFEjr1zCsicMWpAA",
"token_type": "Bearer",
"expires_in": 3600,
"patron": "8362432",
"scope": "read_patron read_fees read_items write_items"
}
Example of a rejected request
HTTP/1.1 403 Forbidden
Content-Type: application/json; charset=utf-8
Cache-Control: no-store
Pragma: no-cache
{
"error": "access_denied",
"code": "403"
}
purpose : Invalidate an access token URL : https://example.org/auth/**logout** request parameters : name occ data type description -------- ------ ----------- ------------------- patron 1..1 string patron identifier -------- ------ ----------- ------------------- response fields : name occ data type description -------- ------ ----------- ------------------- patron 1..1 string patron identifier -------- ------ ----------- -------------------
The logout method invalidates an access token, independent from the previous lifetime of the token. On success, the server MUST invalidate at least the access token that was used to access this method. The server MAY further invalidate additional access tokens that were created for the same patron.
purpose : Change password of a patron URL : https://example.org/auth/**change** scope : change_password request parameters : name occ data type description -------------- ------ ----------- ---------------------------- patron 1..1 string Patron identifier username 1..1 string User name of the patron old_password 1..1 string Password of the patron new_password 1..1 string New password of the patron -------------- ------ ----------- ---------------------------- response fields : name occ data type description -------- ------ ----------- ------------------- patron 1..1 string patron identifier -------- ------ ----------- -------------------
The server MUST check
- the access token
- whether username and password match
- whether the user identified by username has scope
change_password
A PAIA server MAY reject this method and return an error
response with error code access_denied (403) or error code
not_implemented (501). On success, the patron identifier is returned.
access token : A confidential random string that must be sent with each PAIA request for authentification. document : A concrete or abstract document, such as a work, or an edition. item : A concrete copy of a document, for instance a particular physical book. PAIA auth server : HTTP endpoint that implements the PAIA auth specification, so all PAIA auth methods can be accessed at a common base URL. PAIA core server : HTTP endpoint that implements the PAIA core specification, so all PAIA core methods can be accessed at a common base URL. patron : An account of a library user patron identifier : A Unicode string that identifies a library patron account.
Security of OAuth 2.0 with bearer tokens relies on correct application of HTTPS. It is known that SSL certificate errors are often ignored just because of laziness. It MUST be clear to all implementors that this spoils the whole chain of trust and is as secure as sending access tokens in plain text.
To limit the risk of spoiled access tokens, PAIA servers SHOULD put limits on the lifetime of access tokens and on the number of allowed requests per minute among other security limitations.
It is also known that several library systems allow weak passwords. For this reason PAIA auth servers MUST follow approriate security measures, such as protecting against brute force attacks and blocking accounts with weak passwords or with passwords that have been sent unencrypted.
This non-normative section contains additional examples and a mapping to RDF to illustrate the semantics of PAIA concepts and methods.
Six document status data type values are possible. One document can have different status for different patrons and for different times. The following table illustrates reasonable transitions of document status with time for a fixed patron. For instance some document held by another patron is first requested (0 → 1) with PAIA method request, made available after return (1 → 4), picked up (4 → 3), renewed after some time with PAIA method renew (4 → 4) and later returned (3 → 0).
transition → 0 1: reserved 2: ordered 3: held 4: provided 5: rejected
0 = request request loan request request
1: reserved cancel = available loan available patron inactive, document lost ...
2: ordered cancel / = loan available patron inactive, document lost ...
3: held return / / renew / /
4: provided not picked up / / loan = patron inactive, ...
5: rejected time passed patron active patron active / patron active =
Transitions marked with "/" may also be possible in special circumstances: for instance a book ordered from the stacks (status 2) may turn out to be damaged, so it is first repaired and reserved for the patron meanwhile (status 1). Transitions for digital publications may also be different. Note that a PAIA server does not need to implement all document states. A reasonable subset is to only support 0, 1, 3, and 5.
The handling of digital documents is subject to frequently asked questions. The following rules of thumb may help:
- For most digital documents the concept of an item does not make sense and there
is no URI of a particular copy. In this case the
document.editionfield should be used instead ofdocument.item. - For some digital documents there may be no distinction between status
providedand statusheld. The statusprovidedshould be preferred when the same document can be used by multiple patrons at the same time, andheldshould be used when the document can exclusively be used by the patron.
Although PAIA is first defined as HTTP API, it includes a conceptual data model, which can be mapped to RDF among other expressions. The expression of PAIA in RDF is in an early phase of discussion. The mapping to RDF includes the following core concepts:
Patron
: A patron account expressed as instance of sioc:User. The patron account
typically belongs to a person, connected to with foaf:account. The date
of expiration can be expressed with particip:endDate.
Document
: An abstract work, a specific edition, or an item. Probably an instance of
bibo:Document or frbr:Item.
Account state
: The current state of a patron account. Still to be discussed whether modeled
as entity or as relationship.
Document service
: An instance of a library service connected to a patron and a document.
Document services are returned by the PAIA core method items. This
entity could be expressed with DAIA ontology.
Document status
: The current state of a (document) service, defined as subclass instance of
ssso:Service from the Simple Service Status Ontology (SSSO) and as instance
of daia:Service from the Document Availability Information Ontology (DAIA).
Fee
: An amount of money that has to be paid by a patron for some reason.
Each fee can be connected to a document service.
Bradner, S. 1997. “RFC 2119: Key words for use in RFCs to Indicate Requirement Levels.” http://tools.ietf.org/html/rfc2119.
Fielding, R. 1999. “RFC 2616: Hypertext Transfer Protocol.” http://tools.ietf.org/html/rfc2616.
D. Hardt. 2012. “RFC 6749: The OAuth 2.0 Authorization Framework.” http://tools.ietf.org/html/rfc6749.
Jones, M. and Hardt, D. 2012. “RFC 6750: The OAuth 2.0 Authorization Framework: Bearer Token Usage.” http://tools.ietf.org/html/rfc6750.
Rescorla, E. 2000. “RFC 2818: HTTP over TLS.” http://tools.ietf.org/html/rfc2818.
Voss, J. 2012. “DAIA ontology“. http://purl.org/ontology/daia/.
Footnotes
-
The error list was compiled from HTTP and OAuth 2.0 specifications, the Twitter API, the StackExchange API, and the GitHub API. ↩