Internet Engineering Task Force E. Zierau, Ed. Internet-Draft Royal Danish Library Intended status: Informational November 4, 2018 Expires: May 8, 2019 A Persistent Web IDentifier (PWID) URN Namespace draft-pwid-urn-specification-04 Abstract This document specifies a Uniform Resource Name (URN) for Persistent Web IDentifiers to web material in web archives using the 'pwid' namespace identifier. The main purpose of the standard is to support specification of references that are not covered by other reference techniques: to support references to material in web archives with restricted access. Furthermore, it supports persistent technology agnostic references to web archives in general, in a form that can work as an algorithmic basis for finding web archive resources in general. An additional important benefit is that it can be used in specifying web collections, which then can form a persistent computational basis for the extract of the archived collection parts. Since the parts can be specified generally, this further allow collections to be specified with elements from one or more web archives. The PWID is designed for researchers and therefore it is designed as general, global, sustainable, humanly readable, technology agnostic, persistent and precise web references for web materials in web archives. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on May 8, 2019. Zierau Expires May 8, 2019 [Page 1] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5 2. Namespace Registration Template . . . . . . . . . . . . . . . 5 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 4. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.1. Normative References . . . . . . . . . . . . . . . . . . 20 4.2. Informative References . . . . . . . . . . . . . . . . . 20 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 23 1. Introduction The URN PWID is a supplement to existing reference standards, where the PWID will support references to web archives, including areas that are not supported today: support of references to material in web archives with restricted access. Furthermore, it enables technology agnostic references to web archives in general, which can for instance can be needed for references to web material that is dynamic (e.g. a news site) or a specific version of a web material (e.g. specific version of the DOI handbook). The URN PWID is a form that can work as an algorithmic basis for finding the resource. This also enables basis for computation of archived web parts to a collection from one or more web archives. Furthermore, the PWID includes information about the resource which makes it possible to find alternative resources, in cases where the original precise resource have become unavailable. The PWID URN is designed to be a persistent reference that is general, global and technology agnostic in order to enhance its chances for being sustainable. Furthermore, it is designed to be Zierau Expires May 8, 2019 [Page 2] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 humanly readable and with ability to make precision of the web archive resource covers. This design enables a PWID URN to: o be used for technical solutions e.g. to make them resolvable o cover references to all sorts of materials in web archives o cover references to materials from all sort of web archives The motivation for defining a PWID namespace is the growing challenge of references to archived web resources, which the PWID as a URN can assist in overcoming. The standard is needed to address web materials meeting precision and persistency issues on par precision in with traditional references for analogue material. Furthermore, it is needed in order to address web archive resources that are not freely available online. The PWID URN covers both referencing of web resources from research papers and definition of web collection/ corpus. In detail the challenges are: o Citation guidelines generally do not cover general and persistent referencing techniques for web resources that are not registered by Persistent Identifier systems (like DOI [DOI]). However, an increasing number of references point to resources that only exist on the web, e.g. blogs that turned out to have a historical impact. In order to obtain persistency for a reference, the target need to be stable. As the live web is 'alive' and in constant change, persistency can only be obtained by referring to archived snapshots of the web. The PWID URN is therefore focused on referencing archived web material in a technology agnostic way (research documented in [IPRES2016] and [ResawRef]). o There are many new initiatives for web archive referencing, - most of them are centralised solutions which offers harvest and referencing, but these cannot be used for existing materials in web archives. Other initiatives only cover open web archives, which does not cover material in archives with restricted access and where there is a risk of imprecision if a resource in an alternative archive is the result of resolving such a resource. The PWID URN is needed in order to fill these gaps where other techniques are not sufficient. o There are many different requirements for construction of collection definitions for web material besides precision and persistency. Recent research have found that various legal and sustainability issues leads to a need for a collection to be defined by references to the web parts in the collection. The PWID URN is needed in such definitions in order to fulfil these Zierau Expires May 8, 2019 [Page 3] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 requirements and to enable a collection to cover web materials from more archives (research documented in [ResawColl]). The PWID is especially useful for web material where precision is in focus and/or there are references to materials from web archives requiring special grants in order to gain access. The precision regards both pointing to the archive where it was found and validated against its purpose (other archived versions in other web archives may differ both regarding completeness and contents even within short time periods) as well as precision about what is actually referred by the reference (e.g. is it the page or the whole website). Furthermore the PWID is very useful in specification of contents of a web collection (also known as web corpus). Definitions of web collections are often needed for extraction of data used in production of research results, e.g. for evaluations in the future. Current practices today are not persistent as they often use some CDX version, which vary for different implementations. Strict syntax is needed for the PWID reference in order to ensure that it can be used for computational purposes. This is especially relevant for automatic extraction of parts from web collection definitions. Furthermore, readers of research papers are today expecting to be able to access a referenced resource by clicking an actionable URI, therefore a similar facility will be expected for references to available archived web material, which strict syntax can make possible. Examples of technical solutions that is enabled are: o resolving of a references and automatic extraction of web collection defined by PWID URNs [ResawRef] [ResawColl] o Resolving of a PWID reference by resolving services. As a start, there is work on a prototype that can work for the Danish web archive data and open web archives with standard patterns for the current technologies. There may come different implementations for resolving which may rely on different protocols and application The purpose of the PWID is also to express a web archive reference as simple as possible and at the same time meeting requirements for sustainability, usability and scope. Therefore, the PWID URN is focused on only having the minimum required information to make a precise identification of a resource in an arbitrary web archive. Resent research have found that this is obtain by the following information [ResawRef]: o Identification of web archive Zierau Expires May 8, 2019 [Page 4] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 o Identification of source: * Archived URI or identifier * Archival timestamp o Intended precision (page, part, subsite etc.) The PWID URN represents this information in a human readable way as well as a well-defined way that enables technical solutions to interpret the URN. 1.1. Requirements Language 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 [RFC2119]. 2. Namespace Registration Template Namespace Identifier: PWID Version: 4 Date: 2018-11-03 Registrant: Eld Maj-Britt Olmuetz Zierau Royal Danish Library Soeren Kierkegaards Plads 1 1219 Copenhagen Denmark ph: +45 9132 4690 email: elzi@kb.dk Purpose: The URN PWID is a supplement to existing reference standards, where the PWID will support references to web archives, including areas that are not supported today: support of references to Zierau Expires May 8, 2019 [Page 5] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 material in web archives with restricted access. Furthermore it enables technology agnostic references to web archives in general, which can for instance can be needed for references to web material that is dynamic (e.g. a news site) or a specific version of a web material (e.g. specific version of the DOI handbook). The URN PWID is a form that can work as an algorithmic basis for finding the resource. This also enables basis for computation of archived web parts to a collection from one or more web archives. Furthermore, the PWID includes information about the resource which makes it possible to find alternative resources, in cases where the original precise resource have become unavailable. The PWID URN is designed to be a persistent reference that is general, global and technology agnostic in order to enhance its chances for being sustainable. Furthermore, it is designed to be humanly readable and with ability to make precision of the web archive resource covers. This design enables a PWID URN to: * be used for technical solutions e.g. to make them resolvable * cover references to all sorts of materials in web archives * cover references to materials from all sort of web archives The motivation for defining a PWID namespace is the growing challenge of references to archived web resources, which the PWID as a URN can assist in overcoming. The standard is needed to address web materials meeting precision and persistency issues on par precision in with traditional references for analogue material. Furthermore, it is needed in order to address web archive resources that are not freely available online. The PWID URN covers both referencing of web resources from research papers and definition of web collection/corpus. In detail the challenges are: * Citation guidelines generally do not cover general and persistent referencing techniques for web resources that are not registered by Persistent Identifier systems (like DOI [DOI]). However, an increasing number of references point to resources that only exist on the web, e.g. blogs that turned out to have a historical impact. In order to obtain persistency for a reference, the target need to be stable. As the live web is 'alive' and in constant change, persistency can only be obtained by referring to archived snapshots of the web. The PWID URN is therefore focused on referencing archived web Zierau Expires May 8, 2019 [Page 6] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 material in a technology agnostic way (research documented in [IPRES2016] and [ResawRef]). * There are many new initiatives for web archive referencing, - most of them are centralised solutions which offers harvest and referencing, but these cannot be used for existing materials in web archives. Other initiatives only cover open web archives, which does not cover material in archives with restricted access and where there is a risk of imprecision if a resource in an alternative archive is the result of resolving such a resource. The PWID URN is needed in order to fill these gaps where other techniques are not sufficient. * There are many different requirements for construction of collection definitions for web material besides precision and persistency. Recent research have found that various legal and sustainability issues leads to a need for a collection to be defined by references to the web parts in the collection. The PWID URN is needed in such definitions in order to fulfil these requirements and to enable a collection to cover web materials from more archives (research documented in [ResawColl]). The PWID is especially useful for web material where precision is in focus and/or there are references to materials from web archives requiring special grants in order to gain access. The precision regards both regards precise reference where there can be no doubt about that you have the correct web material as well as precision about what is actually referred by the reference (e.g. is it the page or the whole website) Furthermore, the PWID is very useful in specification of contents of a web collection (also known as web corpus). Definitions of web collections are often needed for extraction of data used in production of research results, e.g. for evaluations in the future. Current practices today are not persistent as they often use some CDX version, which vary for different implementations. Strict syntax is needed for the PWID reference in order to ensure that it can be used for computational purposes. This is especially relevant for automatic extraction of parts from web collection definitions. Furthermore, readers of research papers are today expecting to be able to access a referenced resource by clicking an actionable URI, therefore a similar facility will be expected for references to available archived web material, which strict syntax can make possible. Examples of technical solutions that is enabled are: Zierau Expires May 8, 2019 [Page 7] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 * resolving of a references and automatic extraction of web collection defined by PWID URNs [ResawRef] [ResawColl] * Resolving of a PWID reference by resolving services. As a start, there is work on a prototype that can work for the Danish web archive data and open web archives with standard patterns for the current technologies. There may come different implementations for resolving which may rely on different protocols and application The purpose of the PWID is also to express a web archive reference as simple as possible and at the same time meeting requirements for sustainability, usability and scope. Therefore, the PWID URN is focused on only having the minimum required information to make a precise identification of a resource in an arbitrary web archive. Resent research have found that this is obtain by the following information [ResawRef]: * Identification of web archive * Identification of source: + Archived URI or identifier + Archival timestamp * Intended precision (page, part, subsite etc.) The PWID URN represents this information in a human readable way as well as a well-defined way that enables technical solutions to interpret the URN. Syntax: The syntax of the PWID URN is specified below in Augmented Backus- Naur Form (ABNF) [RFC5234] and it conforms to URN syntax defined in [RFC8141]. The syntax definition of the PWID URN is: pwid-urn = "urn" ":" pwid-NID ":" pwid-NSS pwid-NID = "pwid" pwid-NSS = archive-id ":" archival-time ":" precision-spec ":" archived-item archive-id = +( unreserved ) Zierau Expires May 8, 2019 [Page 8] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 precision-spec = "part" / "page" / "subsite" / "site" / "collection" / "recording" / "snapshot" / "other" archived-item = URI / archived-item-id archived-item-id = +( unreserved ) where * 'archival-time' is a UTC timestamp as described in the W3C profile of [ISO8601] [W3CDTF] (also defined in [RFC3339]), for example YYYY-MM-DDThh:mm:ssZ. The 'archival-time' shall represent the timestamp that the web archive have recorded for the referenced archived URI. The archival-time may be specified at any of the levels of granularity described in [W3CDTF], as long as it reflects exactly the granularity of the timestamp recorded in the web archive, which is in accordance with the WARC standard [ISO28500]. * 'unreserved' is defined as in [RFC3986] * 'precision-spec' values are not case sensitive (i.e. "PAGE" / "PART" / "PaGe" / ... are valid values as well.) * 'URI' is defined as in [RFC3986] but where occurrences of "[", "]", "?" and "#" are %-encoded in order not to clash with URN reserved characters [RFC8141] The precision specification is expressing the intended precision of the reference. For example, if the reference is to an html web element, this element can be interpreted in several ways: * As just one web part Meaning the file containing the html, and precisely this file * A web page Meaning that an application like Wayback shows result in a browser, and calculates referenced web parts (display templates, images etc.) and use these found web parts in the result. If the full reference only contains the PWID URN for the page, this may mean that the archived page can change look over time, e.g. in case that parts referred by the page did not exist at reference time, but are harvested at a later stage, - or in case the web archive's algorithm for calculation of the referred web parts are changed and given a different result. In order to make a precise reference to a picture in context of a web page, the most precise reference will be to provide the Zierau Expires May 8, 2019 [Page 9] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 PWID URN for the page (with page precision) and the PWID URN for the image file part which contains the referred picture (with part precision) * As a site or subsite Meaning that an application like Wayback shows result in a browser showing the web page, - and if there are restricted access according to the reference, the application also needs to make sure that all parts/pages belonging to the site/subsite is available. If the full reference only contains the PWID URN for the site/ subsite, this may mean that the site/subsite can change its appearance over time, in the same way as for the web page described above. The precision specification needs to be part of an URN PWID in order to enable the person making the above described precision in the reference. Furthermore this precesion specification will make it possible for resolvers to display the referred source in a way that corresponds to the precision specification. Especially for web materials, there can be different ways to represent e.g. a web page, which provides different precision of the source as well. The above examples with part, page, subsite and site are addressing the most common access via browser functionality like in Wayback. However, there are also web archives that archive snapshots of the web pages for the archived URI. A third option can be to produce a collection of archived URIs as basis for browser access instead of letting the web archive calculate sub items (which may change over time). An example of the production of such a collection is provided in the section about assignment. Lastly, a web page may be archived via a web recording. As consequence of the above, there are following valid precision- spec values: * part the single archived web part harvested as a file from the specified URI, e.g. a pdf, an html text, an image * page the web page represented by the web page file (e.g. html) harvested from the specified URI, where this contents is interpreted as a web page with all referred parts relevant to display the web page (but where referred parts must be calculated as described above), e.g. an html page with referred images Zierau Expires May 8, 2019 [Page 10] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 * subsite The referred web page (as described under 'page') where it is possible to browse to all references starting with the same path as the archived URI * site The referred web page (as described under 'page') where it is possible to browse to all references in the domain specified in the archived URI * collection Representation of a collection specification, where it is up to the web archive applications to find out how it is rendered (e.g. collection specification in the XML format enabling interpretation as in the example provided in [ResawColl]) * snapshot a snapshot (image) representation of web material, e.g. a web page * recording Representation of a web recording specification where it is up to the web archive applications to find out how it is rendered (where interpretation could depends on file-suffix for the web recording), an example is web recording coded in a WARC file * other This is a placeholder to allow reference of a resource of any kind with an assigned identifier (by the archive). In all cases, it will be up to the application serving the web archive to interpret how this item should be rendered Assignment: The PWID URNs does not have to be assigned by an authority, as they are based on the information created at the time of archiving. In other words: the PWID URNs are created independently, but following an algorithm which ensures that the referred item can be found if it is still available. It also has the benefit that it includes information to look alternative resources e.g. via Memento for some open web archives [MEMENTO] or via possibly coming web archive infrastructures. A PWID URN is created by finding the relevant information of the syntax parts of the PWID on form: "urn:pwid:" archive-id ":" archival-time ":" precision-spec ":" archived-item Zierau Expires May 8, 2019 [Page 11] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 The PWID URN for an archived item in hand can be constructed by exchanging the unspecified PWID parts with relevant information, as explained in the following: * archive-id (identification of web archive): In this version of the standard, it is recommended to use the domain of the web archive as the identifier for the web archive (e.g. archive.org for Internet Archives open web archive). This is recommended, since browsing of this domain page typically will lead to description of how to access the web archive, e.g. online or by applying for access grants. Furthermore, it is more precise than e.g. the name of the archive, since there may be more than one installation of web archives in the same organisation, e.g. archive.org and archive-it.org are both covered by Internet Archive. When a registry of web archives are established it will be more precise and persistent to use the web archive identifier specified in this registry (e.g. DKWA for the Danish web archive with domain netarkivet.dk) * archival-time (archival timestamp): The archival time for the archived item in hand may be displayed along with the archived item, but there are different implementation where it is important to be aware of whether a more precise timestamp can be found, and that it is the correct timestamp that is used. For many Wayback implementation the precise time can be found as part of the URI used for viewing the archived item, e.g. in the example of https://web.archive.org/web/20160122112029/http://www.dr.dk viewable by the Internet Archives Wayback installation, the number 20160122112029 represents the archival time 2016-01-22T11:20:29Z. In other installations. In other installations, the most precise time may be found in the URI from a search result leading to the resource (which usually redirects on basis of a call to the underlying archive index). Especially for web pages with frames, there may be cases where the actual time is not displayed with the source, since only the times for the contents of the frames are displayed. * precision-spec (precision as represented page, part, site, snapshot etc.): The precision specification specifies how the user should view the referred item - either as a specific representation (with inherited precision) or by use of tools (e.g. browse web site based on calculations or browse on basis of collection of specific parts). Zierau Expires May 8, 2019 [Page 12] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 Since the archived URI can have different forms indicated by the precision specification, this information may be used in resolution and location. For most imprecision types are the ones that involves calculation, i.e. page, site or subsite. For items like an image that have no references to calculate the precision is best described by part, since it also tells that it is a precise reference. * archived-item (archived URI or identifier): The archived item will be the URI (or identifier assigned for a resource by the archive) of the displayed the archived item in hand. A much easier way to construct PWID URNs is to use tools that construct them. Currently, there is also a prototype for a SOLR- Wayback tool (Source at https://github.com/netarchivesuite/ solrwayback) [PWIDprovider], which can assist in finding the most precise reference to an archived web page. This Wayback version can provide all PWID URNs belonging a shown page (with the page PWID URN at the top). For example, in netarkivet.dk, the archived URI for the web page http://www.susanlegetoej.dk/shop/handskedyr- siameser-killing-8681p.html archived 2008-11-29 01:19:16 UTC, has the following parts calculated by the SOLR-Wayback tool: urn:pwid:netarkivet.dk:2008-11- 29T00:41:42Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_Master_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:39:47Z:part:http://www.susanlegetoej.dk/shop/css/ print.css urn:pwid:netarkivet.dk:2008-11- 29T00:40:06Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_Basket_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:40:00Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_TopMenu_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:40:00Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_SearchPage_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:40:35Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_Productmenu_NF.css Zierau Expires May 8, 2019 [Page 13] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 urn:pwid:netarkivet.dk:2008-11- 29T00:40:22Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_SpaceTop_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:40:24Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_SpaceLeft_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:40:23Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_SpaceBottom_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:40:25Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_SpaceRight_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:37:23Z:part:http://www.susanlegetoej.dk/images/ddcss/ SK113_ProductInfo_NF.css urn:pwid:netarkivet.dk:2008-11- 29T00:37:24Z:part:http://www.susanlegetoej.dk/Shop/js/ Variants.js urn:pwid:netarkivet.dk:2009-03- 03T11:53:00Z:part:http://www.susanlegetoej.dk/Shop/js/Media.js urn:pwid:netarkivet.dk:2009-03- 03T11:53:02Z:part:http://www.susanlegetoej.dk/images/design/ print.gif urn:pwid:netarkivet.dk:2009-03- 03T11:54:19Z:part:http://www.susanlegetoej.dk/Shop/js/Scroll.js urn:pwid:netarkivet.dk:2009-03- 03T11:54:09Z:part:http://www.susanlegetoej.dk/Shop/js/ Shop5Common.js urn:pwid:netarkivet.dk:2006-11- 20T20:16:03Z:part:http://www.susanlegetoej.dk/images/602551.jpg Security and Privacy: Security and privacy considerations are restricted to accessible web resources in web archives. Resolvers to PWID URNs will usually only be possible using the web archives' access tools, where security and privacy are covered by these tools. In such cases security and privacy will covered by such tools, since the Zierau Expires May 8, 2019 [Page 14] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 information used for access has no security and privacy issues. In the cases where resolution is made around the archives' access tools, there should be made separate analysis. Interoperability: This is covered by comments in the Syntax description: * the PWID URN conforms to the URI standard defined as in RFC 3986 [RFC3986] and the URN standard RFC 8141 [RFC8141] * the 'archival-time' of the PWID URN conforms UTC timestamp as described in the W3C profile of ISO 8601 [ISO8601] [W3CDTF] and is in accordance with the WARC standard ISO 28500 [ISO28500]. * the 'archived-item' is either an assigned identifier (the URN standard RFC 8141 [RFC8141]) or an URI which conforms to the URI standard defined as in RFC 3986 [RFC3986], with %-encodings of "[", "]", "#", and "?" in order to conform to the the URN standard RFC 8141 [RFC8141] Resolution: The information in a PWID URN can be used for locating a web archive resource, for any kind of web archive. It includes the minimum information for web archive materials, which enables resolvability, manually or by a resolver. Resolution of a PWID URN is the primary motivation of making a formal URN definition, instead of just textual representation of the for needed parts of a PWID. Resolution (manually or automatically) is done based on the PWID parts: * Web archive identification for web archive holding referred resource The identifier is either an identifier where location of the web archive can be found by looking up the identifier in a registry, - or it is the domain name for the web archive, where browsing this domain page typically will lead to description of how to access the web archive, e.g. online or by applying for access grants * Archived URI or identifier of archived item If the resource is an archived URI, this URI must be used in search for or construction of location of the resource. If the resource is an identifier assigned to the resource (by the Zierau Expires May 8, 2019 [Page 15] Internet-DraftA Persistent Web IDentifier (PWID) URN NamespNovember 2018 archive), it is this identifier that must be used in search for or construction of location of the resource * Date and time associated with the archived item The archival date and time must be used in search for or construction of the location of the resource * Precision of what is referred The precision can either contribute to the guidance of activating tools to view the referred item e.g. browse the referred item as a page on basis of computed closest past, browse the referred item on basis of parts specified in a collection, or view the referred item as a snapshot. In the example of the snapshot, it also contains a specification of which resource to display In the following the different resolution techniques are explained (manual as well as via a service) . An example of a PWID URN is: urn:pwid:archive.org:2016-01-22T11:20:29Z:page:http://www.dr.dk has the information: * archive.org Currently known identifier in form of the Internet Archive domain name for their open access web archive. If Internet Archive registered their open web archive in an IANA web archive register, this identifier could currently be "web.archive.org/web/" for Wayback resolution, or it could be "archive.org/pwid/" if a PWID interface was created as described below * 2016-01-22T11:20:29Z UTC date and time associated with the archived URI * page Clarification that the reference cover the full web page with all its inherited parts selected by the web archive * http://www.dr.dk archived URI of item Based on the current (2018) knowledge of Internet Archive's open access web interface, which has the pattern: https://web.archive.org/web/