The Atom Publishing Protocol

The Atom Publishing Protocol BitWorking, Inc

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Propylon Ltd.

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The Atom Publishing Protocol (APP) is an application-level protocol for publishing and editing Web resources. The protocol is based on HTTP transport of Atom-formatted representations. The Atom format is documented in the Atom Syndication Format (RFC4287). To provide feedback on this Internet-Draft, join the atom-protocol mailing list (http://www.imc.org/atom-protocol/index.html).

The Atom Publishing Protocol is an application-level protocol for publishing and editing Web resources using HTTP and XML 1.0 . The protocol supports the creation of arbitrary web resources and provides facilities for: Collections: Sets of resources, which can be retrieved in whole or in part. Introspection: Discovering and describing collections. Editing: Creating, updating and deleting resources.

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 . Note: The Introspection Document allows the use of IRIs , as well as URIs . Every URI is an IRI, so any URI can be used where an IRI is needed. How to map an IRI to a URI is specified in Section 3.1 of Internationalized Resource Identifiers (IRIs) .

For convenience, this protocol can be referred to as the "Atom Protocol" or "APP". URI/IRI - A Uniform Resource Identifier and Internationalized Resource Identifier. These terms and the distinction between them are defined in and . Note that IRIs are mapped to URIs before dereferencing takes place. Resource - A network-accessible data object or service identified by an IRI, as defined in . See for further discussion on resources. The phrase "the URI of a document" in this specification is shorthand for "an URI which, when dereferenced, is expected to produce that document as a representation". Representation - An entity included with a request or response as defined in . Collection - A resource that contains a set of member IRIs. See . Member - A resource whose IRI is listed in a Collection. Introspection Document - A document that describes the location and capabilities of one or more Collections. See .

The Atom Publishing Protocol uses HTTP to edit and author web resources. The Atom Protocol uses the following HTTP methods: GET is used to retrieve a representation of a resource or perform a query. POST is used to create a new, dynamically-named resource. PUT is used to update a known resource. DELETE is used to remove a resource. Along with operations on resources the Atom Protocol provides structures, called Collections, for managing and organising resources, called Members. Collections contain the IRIs of, and metadata about, their Member resources. Atom Protocol clients can use Introspection documents, which represent server-defined groups of Collections, to initialize the process of creating and editing resources. Note that when an IRI is used for resource retrieval over HTTP, the IRI is first converted to a URI according the procedure defined in section 3.1. The resource that the IRI locates is the same as the one located by the URI obtained after converting the IRI.

Client Server | | | 1.) GET to URI of Introspection Document | |------------------------------------------>| | | | 2.) Introspection Document | |<------------------------------------------| | | The client sends a GET request to the URI of the Introspection Document. The server responds with the document enumerating the IRIs of a set of Collections and the capabilities of those Collections supported by the server. The content of this document can vary based on aspects of the client request, including, but not limited to, authentication credentials.

Client Server | | | 1.) POST to URI of Collection | |------------------------------------------>| | | | 2.) 201 Created | |<------------------------------------------| | | The client POSTs a representation of the Member to the URI of the collection. If the Member resource was created successfully, the server responds with a status code of 201 and a Location: header that contains the URI of the newly created resource.

Once a resource has been created and its URI is known, that URI can be used to retrieve, update, and delete the resource.

Client Server | | | 1.) GET to Member URI | |------------------------------------------>| | | | 2.) Member Representation | |<------------------------------------------| | | The client sends a GET request to the Member's URI to retrieve its representation. The server responds with the representation of the resource.

Client Server | | | 1.) PUT to Member URI | |------------------------------------------>| | | | 2.) 200 OK | |<------------------------------------------| The client PUTs an updated representation to the Member's URI. Upon a successful update of the resource the server responds with a status code of 200.

Client Server | | | 1.) DELETE to Member URI | |------------------------------------------>| | | | 2.) 200 Ok | |<------------------------------------------| | | The client sends a DELETE request to the Member's URI. Upon the successful deletion of the resource the server responds with a status code of 200.

To list the members of a Collection the client sends a GET request to the Collection's URI. An Atom Feed Document is returned containing one Atom Entry for each member resource. See and for a description of the feed contents.

Client Server | | | 1.) GET to Collection URI | |------------------------------->| | | | 2.) 200 OK, Atom Feed Doc | |<-------------------------------| | | The client sends a GET request to the Collection's URI. The server responds with an Atom Feed Document containing the IRIs of the collection members.

The Atom Protocol uses the response status codes defined in HTTP to indicate the success or failure of an operation. Consult the HTTP specification for detailed definitions of each status code. It is RECOMMENDED that entities contained within HTTP 4xx and 5xx responses include a human-readable explanation of the error.

The Atom Protocol Introspection format is specified in terms of the XML Information Set , serialised as XML 1.0 . Atom Publishing Protocol Documents MUST be well-formed XML. This specification does not define any DTDs for Atom Protocol, and hence does not require them to be "valid" in the sense used by XML.

This specification uses a shorthand for two common terms: the phrase "Information Item" is omitted when discussing Element Information Items and Attribute Information Items. Therefore, when this specification uses the term "element," it is referring to an Element Information Item in Infoset terms. Likewise, when it uses the term "attribute," it is referring to an Attribute Information Item.

The namespace name for the XML format described in this specification is:

http://purl.org/atom/app# This specification uses the prefix "app:" for the namespace name. The choice of namespace prefix is not semantically significant. The "app:" namespace is reserved for future forward-compatible revisions of the Atom Publishing Protocol. Future versions of this specification could add new elements and attributes to the markup vocabulary. Software written to conform to this version of the specification will not be able to process such markup correctly and, in fact, will not be able to distinguish it from markup error. For the purposes of this discussion, unrecognized markup from the Atom Publishing Protocol vocabulary will be considered "foreign markup". This specification also uses the prefix "atom:" for "http://www.w3.org/2005/Atom", the namespace name of the Atom Syndication Format .

XML elements defined by this specification MAY have an xml:base attribute . When xml:base is used, it serves the function described in section 5.1.1 of URI Generic Syntax , establishing the base URI (or IRI) for resolving any relative references found within the effective scope of the xml:base attribute. Any element defined by this specification MAY have an xml:lang attribute, whose content indicates the natural language for the element and its descendents. The language context is only significant for elements and attributes declared to be "Language-Sensitive" by this specification. Requirements regarding the content and interpretation of xml:lang are specified in Section 2.12 of XML 1.0 .

appCommonAttributes = attribute xml:base { atomUri }?, attribute xml:lang { atomLanguageTag }?, undefinedAttribute*

Some sections of this specification are illustrated with fragments of a non-normative RELAX NG Compact schema . A complete schema appears in . However, the text of this specification provides the definition of conformance.

For authoring to commence, a client needs to first discover the capabilities and locations of the available collections. Introspection documents are designed to support this discovery process. An Introspection Document describes workspaces, which are server-defined groupings of collections. Introspection documents are identified with the "application/atomserv+xml" media type (see ). While an introspection document allows multiple workspaces, there is no requirement that a server support multiple workspaces. In addition, a collection MAY appear in more than one workspace.

This Introspection Document describes two workspaces. The first, called "Main Site", has two collections called "My Blog Entries" and "Pictures" whose IRIs are "http://example.org/reilly/main" and "http://example.org/reilly/pic" respectively. The "Pictures" includes an accept element indicating that client can post image files to the collection to create new entries. Entries with associated media resources are discussed in section 8.3. The second workspace is called "Side Bar Blog" and has a single collection called "Remaindered Links" whose collection IRI is "http://example.org/reilly/list".

The root of an introspection document is the "app:service" element. The "app:service" element is the container for introspection information associated with one or more workspaces. An app:service element MUST contain one or more app:workspace elements.

namespace app = "http://purl.org/atom/app#" start = appService

The "app:workspace" element contains information elements about the collections of resources available for editing. The app:workspace element MAY contain zero or more app:collection elements.

In an app:workspace element, the first app:collection element MUST refer to the preferred or primary collection. In the following example, the "Entries" collection would be considered the preferred collection:

image/* ]]>

The app:workspace element MUST contain a "title" attribute, which gives a human-readable name for the workspace. This attribute is Language-Sensitive.

The "app:collection" describes an Atom Protocol collection. One child element is defined here for app:collection: "app:accept".

In an Atom feed, the app:collection element MAY appear as a child of an atom:feed or atom:source element to identify the collection to which new entries can be added to the feed.

The app:collection element MUST contain a "title" attribute, whose value gives a human-readable name for the collection. This attribute is Language-Sensitive.

The app:collection element MUST contain a "href" attribute, whose value gives the IRI of the collection.

The app:collection element MAY contain one "app:accept" element. The app:accept element value specifies a comma-separated list of media-ranges identifying the types of representations that can be POSTed to the Collection's URI. Whitespace separating the media-range values is considered insignificant and MUST be ignored. The app:accept element is similar to the HTTP Accept request-header with the exception that app:accept has no notion of preference. Accordingly, the value syntax of app:accept does not use accept-params or "q" parameters as specified in , section 14.1. The order of media-ranges is not significant. The following lists are all equivalent:

image/png, image/* image/*, image/png image/*]]> A value of "entry" indicates that Atom Entry Documents can be posted to the Collection. If the accept element is omitted, or empty, clients SHOULD assume that only Atom Entry documents will be accepted by the collection.

To add members to a collection, clients send POST requests to the collection's URI. Collections MAY impose constraints on the media-types of request entities POSTed to the collection and MAY generate a response with a status code of 415 ("Unsupported Media Type"). If an entry was created in the collection which received the POST, its URI MUST be returned in an HTTP Location header. When the server generates a response with a status code of 201 ("Created"), it SHOULD also return a response body, which, if provided, MUST be an Atom Entry Document representing the newly-created resource. Clients MUST NOT assume that an Atom Entry returned is a full representation of the member resource. Since the server is free to alter the posted entry, for example by changing the content of the "id" element. returning the entry as described in the previous paragraph can be useful to the client, enabling it to correlate the client and server views of the new entry. When the POST request contains an Atom Entry Document, the response from the server SHOULD contain a Content-Location header that contains the same character-by-character value as the Location header. Clients MUST NOT assume that the URI provided by the Location header can be used to edit the created entry. The request body of the POST need not be an Atom entry. For example, it might be a picture, or a movie. For a discussion of the issues in posting such content, see .

Below, the client sends a POST request containing an Atom Entry representation to the URI of the Collection:

Atom-Powered Robots Run Amok urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2003-12-13T18:30:02Z John Doe Some text. ]]> The server signals a successful creation with a status code of 201. The response includes a "Location" header indicating the URI of the Atom Entry and a representation of that Entry in the body of the response.

Atom-Powered Robots Run Amok urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2003-12-13T18:30:02Z John Doe Some text. ]]> Note that the Entry created by the server might not match exactly the Entry POSTed by the client. In particular, a server MAY change the values of various elements in the Entry such as the atom:id, atom:updated and atom:author values and MAY choose to remove or add other elements and attributes, or change element and attribute values. In particular, the publishing system in this example filled in some values not provided in the original POST. For example, presumably it ascertained the author's name via the authentication protocol used to establish the right to post.

Each member Entry within a collection SHOULD contain an atom:link element with a link relation of "edit" that contains the IRI used to retrieve, update or delete the member Entry.

As discussed above, if the body of a client's POST is an Atom Entry document, this constitutes a request that the server create a new entry in the collection to which the POST is addressed and return its URI. If the body of the client's POST is of a media type other than application/atom+xml, this constitutes a request that the server create a new resource as represented by the body of the post, called a "media resource", and also an entry in the collection to which the POST was addressed, called a "media link entry", and return both URIs. If the server successfully creates a media resource and media link entry pair, the Location header included in the response MUST be that of the media link entry. The media link entry MUST have a "content" element with a "src" attribute which links to the media resource. The intent is that the media link entry be used to store metadata about the (perhaps non-textual) media resource, so that the media and the metadata can be retrieved and updated separately. A media link entry SHOULD contain an atom:link element with a link relation of "edit-media" that contains the IRI used to modify the media resource. Deletion of a media link entry SHOULD result in the deletion of the linked media resource. Implementors will note that per the requirements of , media link entries MUST contain an atom:summary element. Upon successful creation of a media link entry, a server MAY choose to populate the atom:summary element (as well as other required elements such as atom:id, atom:author and atom:title) with content derived from the POSTed media resource or from any other source. A server might not allow a client to modify the server selected values for these elements. Note that this specification covers the cases when the POST body is an Atom Entry, and when it is of a non-Atom media type. It does not specify any request semantics or server behavior in the case where the POST media-type is application/atom+xml but the body is something other than an Atom Entry.

A POST whose body is not of the Atom media type and which thus requests the creation of a media resource SHOULD contain a Title: header indicating the client's suggested title for the resource. For example:

The server MAY use the content of the Title: header, as provided or in a modified form, in constructing a title for the resource, which would presumably appear in the media link entry.

The syntax of this header MUST conform to the augmented BNF grammar in section 2.1 of the HTTP/1.1 specification . The [TEXT] rule is described in section 2.2 of the same document. Words of *TEXT MAY contain characters from character sets other than only when encoded according to the rules of .

Below, the client sends a POST request containing a PNG image to the URI of the Collection:

The server signals a successful creation with a status code of 201. The response includes a "Location" header indicating the URI of the media link entry and a representation of that entry in the body of the response. The media link entry includes a content element with a src attribute referencing the media resource, and a link using the link relation "edit-media" specifying the IRI to be used for modifying the media resource.

A picture of the beach urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2003-12-13T18:30:02Z John Doe

]]>

To avoid unintentional loss of data when editing entries or media link entries, Atom Protocol clients SHOULD preserve all metadata, including unknown foreign markup as defined in Section 6 of , which has not been intentionally modified.

Collection resources MUST provide representations in the form of Atom Feed documents whose entries represent the collection's members. Each entry in the Feed Document SHOULD have an atom:link element with a relation of "edit" (See ). The entries in the returned Atom Feed MUST be ordered by their "atom:updated" property, with the most recently updated entries coming first in the document order. Clients SHOULD be constructed in consideration of the fact that changes which do not alter the entry's atom:updated value will not affect the position of the entry in a collection. Clients MUST NOT assume that an Atom Entry returned in the Feed is a full representation of a member resource and SHOULD perform a GET on the member resource before editing. Collections can contain large numbers of resources. A naive client such as a web spider or web browser could be overwhelmed if the response to a GET contained every entry in the collection, and the server would waste large amounts of bandwidth and processing time on clients unable to handle the response. For this reason, servers MAY return a partial listing containing the most recently updated member resources. Such partial feed documents MUST have an atom:link with a "next" relation whose "href" value is the URI of the next partial listing of the collection (the least recently updated member resources) where it exists. This is called "collection paging".

The returned Atom feed MAY NOT contain entries for all the collection's members. Instead, the Atom feed document MAY contain link elements with "rel" attribute values of "next", "previous", "first" and "last" that can be used to navigate through the complete set of matching entries. For instance, suppose a client is supplied the URI "http://example.org/entries/go" of a collection of member entries, where the server as a matter of policy avoids generating feed documents containing more than 10 entries. The Atom feed document for the collection will then represent the first 'page' in a set of 10 linked feed documents. The "first" relation will reference the initial feed document in the set and the "last" relation references the final feed document in the set. Within each document, the "next" and "previous" link relations reference the preceding and subsequent documents.

... ]]> The "next" and "previous" link elements for the feed 'page' located at "http://example.org/entries/2" would look like this:

... ]]>

The Atom Protocol adds the value "edit" to the Atom Registry of Link Relations (see section 7.1 of ). The value of "edit" specifies that the value of the href attribute is the IRI of an editable Atom Entry Document. When appearing within an atom:entry, the href IRI MAY be used to update and delete the resource represented by that entry. An atom:entry MUST contain no more than one "edit" link relation.

The Atom Protocol adds the value "edit-media" to the Atom Registry of Link Relations (see section 7.1 of ). When appearing within an atom:entry, the value of the href attribute is an IRI that MAY be used to modify a media resource associated with that entry. An atom:entry MAY contain zero or more "edit-media" link relations. An atom:entry MUST NOT contain more than one atom:link element with a rel attribute value of "edit-media" that has the same type and hreflang attribute values. All "edit-media" link relations in the same entry reference the same resource. If a client encounters multiple "edit-media" link relations in an entry then it SHOULD choose a link based on the client preferences for type and hreflang. If a client encounters multiple "edit-media" link relations in an entry and has no preference based on the type and hreflang attributes then the client SHOULD pick the first "edit-media" link relation in document order.

This specification defines an Atom Format extension for publishing control called Atom Publishing Control. The namespace name for the Atom Publishing Control's XML vocabulary is "http://example.net/appns/". This specification uses "pub:" for the namespace prefix. The choice of namespace prefix is not semantically significant.

namespace pub = "http://example.net/appns/" pubControl = element pub:control { atomCommonAttributes, pubDraft? & extensionElement } pubDraft = element pub:draft { "yes" | "no" } The "pub:control" element MAY appear as a child of an "atom:entry" which is being created or updated via the Atom Publishing Protocol. The "pub:control" element, if it does appear in an entry, MUST only appear at most one time. The "pub:control" element is considered foreign markup as defined in Section 6 of . The "pub:control" element and its child elements MAY be included in Atom Feed or Entry Documents. The "pub:control" element MAY contain exactly one "pub:draft" element as defined here, and MAY contain zero or more extension elements as outlined in Section 6 of . Both clients and servers MUST ignore foreign markup present in the pub:control element.

The number of "pub:draft" elements in "pub:control" MUST be zero or one. Its value MUST be one of "yes" or "no". A value of "no" means that the entry MAY be made publicly visible. If the "pub:draft" element is missing then the value MUST be understood to be "no". The inclusion of the pub:draft element represents a request by the client to control the visibility of an entry and the pub:draft element MAY be ignored by the server.

All instances of publishing Atom Format entries SHOULD be protected by authentication to prevent posting or editing by unknown sources. note: this section is currently under discussion.

The security of the Atom Protocol is based on note: refers to incomplete section. note: talk here about denial of service attacks using large XML files, or the billion laughs DTD attack.

An Atom Publishing Protocol Introspection Document, when serialized as XML 1.0, can be identified with the following media type: application atomserv+xml None. This parameter has identical semantics to the charset parameter of the "application/xml" media type as specified in . Identical to those of "application/xml" as described in , section 3.2. As defined in this specification. update upon publication In addition, as this media type uses the "+xml" convention, it shares the same security considerations as described in , section 10. There are no known interoperability issues. This specification. update upon publication No known applications currently use this media type. Additional information: As specified for "application/xml" in , section 3.2. .atomsrv As specified for "application/xml" in , section 5. As specified in , section 6. TEXT Joe Gregorio <joe@bitworking.org> COMMON This specification's author(s). update upon publication

&rfc2119; &rfc2616; &rfc4287; &rfc3023; &rfc3986; &rfc3987; &rfc2047; &XML; &XMLNS; &XMLBASE; &INFOSET; &ISO88591; &WEBARCH; RELAX NG Compact Syntax

The content and concepts within are a product of the Atom community and the Atompub Working Group.

This appendix is informative. The Relax NG schema explicitly excludes elements in the Atom Protocol namespace which are not defined in this revision of the specification. Requirements for Atom Protocol processors encountering such markup are given in Section 6.2 and Section 6.3 of .

draft-ietf-atompub-protocol-09: PaceWorkspaceMayHaveCollections, PaceMediaEntries5, http://www.imc.org/atom-protocol/mail-archive/msg05322.html, and http://www.imc.org/atom-protocol/mail-archive/msg05272.html draft-ietf-atompub-protocol-08: added infoset ref; added wording re IRI/URI; fixed URI/IRI ; next/previous fixed as per Atom LinkRelations Attribute (http://www.imc.org/atom-protocol/mail-archive/msg04095.html); incorporated: PaceEditLinkMustToMay; PaceMissingDraftHasNoMeaning, PaceRemoveMemberTypeMust, PaceRemoveMemberTypePostMust, PaceTitleHeaderOnlyInMediaCollections, PacePreserveForeignMarkup, PaceClarifyTitleHeader, PaceClarifyMediaResourceLinks, PaceTwoPrimaryCollections; draft-ietf-atompub-protocol-07: updated Atom refs to RFC4287; incorporated PaceBetterHttpResponseCode; PaceClarifyCollectionAndDeleteMethodByWritingLessInsteadOfMore; PaceRemoveAcceptPostText; PaceRemoveListTemplate2; PaceRemoveRegistry; PaceRemoveWhoWritesWhat; PaceSimplifyClarifyBetterfyRemoveBogusValidityText; PaceCollectionOrderSignificance; PaceFixLostIntrospectionText; PaceListPaging; PaceCollectionControl; element typo in Listing collections para3 (was app:member-type, not app:list-template); changed post atom entry example to be valid. Dropped inline use of 'APP'. Removed nested diagram from section 4. Added ed notes in the security section. draft-ietf-atompub-protocol-06 - Removed: Robert Sayre from the contributors section per his request. Added in PaceCollectionControl. Fixed all the {daterange} verbage and examples so they all use a dash. Added full rnc schema. Collapsed Introspection and Collection documents into a single document. Removed {dateRange} queries. Renamed search to list. Moved discussion of media and entry collection until later in the document and tied the discussion to the Introspection element app:member-type. draft-ietf-atompub-protocol-05 - Added: Contributors section. Added: de hOra to editors. Fixed: typos. Added diagrams and description to model section. Incorporates PaceAppDocuments, PaceAppDocuments2, PaceSimplifyCollections2 (large-sized chunks of it anyhow: the notions of Entry and Generic resources, the section 4 language on the Protocol Model, 4.1 through 4.5.2, the notion of a Collection document, as in Section 5 through 5.3, Section 7 "Collection resources", Selection resources (modified from pace which talked about search); results in major mods to Collection Documents, Section 9.2 "Title: Header" and brokeout para to section 9.1 Editing Generic Resources). Added XML namespace and language section. Some cleanup of front matter. Added Language Sensitivity to some attributes. Removed resource descriptions from terminology. Some juggling of sections. See: http://www.imc.org/atom-protocol/mail-archive/msg01812.html. draft-ietf-atompub-protocol-04 - Add ladder diagrams, reorganize, add SOAP interactions draft-ietf-atompub-protocol-03 - Incorporates PaceSliceAndDice3 and PaceIntrospection. draft-ietf-atompub-protocol-02 - Incorporates Pace409Response, PacePostLocationMust, and PaceSimpleResourcePosting. draft-ietf-atompub-protocol-01 - Added in sections on Responses for the EditURI. Allow 2xx for response to EditURI PUTs. Elided all mentions of WSSE. Started adding in some normative references. Added the section "Securing the Atom Protocol". Clarified that it is possible that the PostURI and FeedURI could be the same URI. Cleaned up descriptions for Response codes 400 and 500. Rev draft-ietf-atompub-protocol-00 - 5Jul2004 - Renamed the file and re-titled the document to conform to IETF submission guidelines. Changed MIME type to match the one selected for the Atom format. Numerous typographical fixes. We used to have two 'Introduction' sections. One of them was moved into the Abstract the other absorbed the Scope section. IPR and copyright notifications were added. Rev 09 - 10Dec2003 - Added the section on SOAP enabled clients and servers. Rev 08 - 01Dec2003 - Refactored the specification, merging the Introspection file into the feed format. Also dropped the distinction between the type of URI used to create new entries and the kind used to create comments. Dropped user preferences. Rev 07 - 06Aug2003 - Removed the use of the RSD file for auto-discovery. Changed copyright until a final standards body is chosen. Changed query parameters for the search facet to all begin with atom- to avoid name collisions. Updated all the Entries to follow the 0.2 version. Changed the format of the search results and template file to a pure element based syntax. Rev 06 - 24Jul2003 - Moved to PUT for updating Entries. Changed all the mime-types to application/x.atom+xml. Added template editing. Changed 'edit-entry' to 'create-entry' in the Introspection file to more accurately reflect its purpose. Rev 05 - 17Jul2003 - Renamed everything Echo into Atom. Added version numbers in the Revision history. Changed all the mime-types to application/atom+xml. Rev 04 - 15Jul2003 - Updated the RSD version used from 0.7 to 1.0. Change the method of deleting an Entry from POSTing <delete/> to using the HTTP DELETE verb. Also changed the query interface to GET instead of POST. Moved Introspection Discovery to be up under Introspection. Introduced the term 'facet' for the services listed in the Introspection file. Rev 03 - 10Jul2003 - Added a link to the Wiki near the front of the document. Added a section on finding an Entry. Retrieving an Entry now broken out into its own section. Changed the HTTP status code for a successful editing of an Entry to 205. Rev 02 - 7Jul2003 - Entries are no longer returned from POSTs, instead they are retrieved via GET. Cleaned up figure titles, as they are rendered poorly in HTML. All content-types have been changed to application/atom+xml. Rev 01 - 5Jul2003 - Renamed from EchoAPI.html to follow the more commonly used format: draft-gregorio-NN.html. Renamed all references to URL to URI. Broke out introspection into its own section. Added the Revision History section. Added more to the warning that the example URIs are not normative.