Internet-Draft M. Toomim Expires: Apr 10, 2020 Invisible College Intended status: Proposed Standard G. Little Invisible College R. Walker Bard College B. Bellomy Invisible College J. Gentle Invisible College Oct 23, 2023 \=/====\\ |//===\\= /=\ =\==\|\=/== =|====\== ||/ |\\ ||\ |\\ /|| \|\ |// //| \\\ |\\ |// |\\ |// //| \\\ \\\ /\/ ||| \=|====|= |/====/=\ /=\/====|=\ =\= \\= =/= //\ /\\ //| |\\ |/| ||| \\\ ||| |// ||| ||| |\\ |// |\/ \|/ /|\ |=\ |\\ =\=\==/=/ ==| |\= ||= /== ===/=|=\=== |==\===// Braid-HTTP: Synchronization for HTTP draft-toomim-httpbis-braid-http-03 Abstract Braid is a set of extensions that generalize HTTP from a state *transfer* protocol into a full state *synchronization* protocol. Braid is composed of four independent extensions to HTTP: 1. VERSIONING of resource history 2. SUBSCRIPTIONS to updates over time 3. PATCHES to ranges of space 4. MERGE-TYPES that specify OT or CRDT behavior Each extension provides a distinct value for a stand-alone use-case. However, they can compose together to support the full power of CRDTs and Operational Transforms on web resources. This allows multiple writers to make simultaneous mutations to arbitrary content-types, under arbitrary network delays and partitions, while guaranteeing consistency across multiple clients and servers. This improves web caching and network performance, and enables natively peer-to-peer, collaboratively-editable, local-first web applications. 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), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://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." The list of current Internet-Drafts can be accessed at https://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at https://www.ietf.org/shadow.html Table of Contents 1. Introduction ..................................................4 1.1. HTTP applications need state Synchronization ................4 1.2. The General Challenge of State Synchronization ..............4 1.3. Braid extends HTTP for State Synchronization ................5 2. Versioning for Resources ......................................6 2.1. Comparison with ETag ........................................6 2.2. PUT a new version ...........................................7 2.3. GET a specific version ......................................8 2.4. GET a range of historical versions ..........................9 2.5. Rules for Version and Parents headers ......................10 3. Updates can be expressed as Patches or Snapshots .............11 3.1. PUT an update as a patch ...................................12 3.2. GET an update as a patch ...................................13 3.3. PUT an update as a set of patches ..........................14 3.3. PUT an update as a custom patch-type .......................15 4. Subscriptions for GET ........................................16 4.1. Creating a Subscription ....................................17 4.2. Sending multiple updates per GET ...........................18 4.3. Continuing a Subscription ..................................19 4.4. Ending a Subscription ......................................20 4.5. Signaling "all caught up" ..................................21 4.6. Errors .....................................................21 5. Design Goals..................................................22 6. Use Cases ....................................................22 6.1. Dynamic Resources ..........................................22 6.2. Dynamic Proxies and Caches .................................23 6.3. A Serverless Chat Example ..................................23 7. Related Work .................................................24 7.1. Existing IETF Standards ....................................24 7.3. IETF Work in Progress ......................................24 7.3. Web Frameworks .............................................23 8. IANA Considerations ..........................................24 8.1. Header Field Registration ..................................24 9. Security Considerations ......................................24 10. Conventions .................................................24 11. Copyright Notice .............................................25 12. References ...................................................25 12.1. Normative References .......................................25 12.2. Informative References .....................................26 13. Acknowledgements .............................................27 14. Authors' Addresses ...........................................28 1. Introduction 1.1. HTTP applications need state Synchronization, not just Transfer HTTP [RFC9110] transfers a static version of state within a single request and response. If the state changes, HTTP does not automatically update clients with the new versions. This design satisficed when webpages were mostly static and written by hand; however today's websites are dynamic, generated from layers of state in databases, and provide realtime updates across multiple clients and servers. Programmers today need to *synchronize*, not just *transfer* state, and to do this, they must work around HTTP. The web has a long history of these workarounds. The original web required users to click reload when a page changed. XMLHTTPRequest [XHR] made it possible to update just part of a page, running a GET request behind the scenes. However, a GET request still could not push updates. To work around this, web programmers would poll the resource with repeated GETs, which was inefficient. Long-polling was invented to reduce redundant requests, but still requires the client to initiate a round-trip for each update. Server-Sent Events [SSE] finally created a standard for the server to push events, but SSE provides semantics of an event-stream, not an update-stream, and SSE programmers must encode the semantics of updating a resource within the event stream. Today there is still no standard way for a server to update its clients when a resource changes. In practice, web programmers today often give up on using standards for "data that changes", and instead send custom messages over a WebSocket -- a hand-rolled synchronization protocol. Unfortunately, this forfeits the benefits of HTTP and ReST, such as caching and a uniform interface [REST]. As the web becomes increasingly dynamic, web applications are forced to implement additional layers of non-standard Javascript frameworks to synchronize changes to state. 1.2. The General Challenge of State Synchronization Part of the issue is that general case of the state synchronization problem is inherently complex. Programmers find it easy to implement a single update, for a single use-case, but it becomes difficult to support multiple writers, for multiple types of edits, with robust conflict resolution, offline edits, and different merge semantics on arbitrary content types, network topologies, and network conditions. Recent research on OT, CRDT, and Version Control algorithms have solved many of these problems in the last decade -- but even today, each OT or CRDT algorithm proposes a different protocol, creating lock-in. However, recent research by these authors has demonstrated that although despite having different protocols; the information each algorithm needs to send over the wire is equivalent. Thus, it is possible to design a general protocol that supports any OT, CRDT, or Version Control algorithm. 1.3. Braid extends HTTP for State Synchronization Braid-HTTP expresses this general model of synchronization in four extensions to HTTP: 1. Versioning (Section 2) Each resource has a history of changes, ordered in time. 2. Patches (Section 3) Each resource can express updates as either *snapshots* or *patches*; bidrectionally as client->server and server->client. 3. Subscriptions (Section 4) A Subscribe header can be added to GET requests. The server responds by pushing future versions to the client while the request is open. 4. Merge Types [MERGE-TYPES] If multiple clients and servers simultaneously edit the same resource, they can guarantee a consistent resulting state by implementing the same Merge Type. Resources specify their Merge Type with a header. Each extension provides standalone value, and can be used separately. For instance, a /current-temp URL can implement Subscriptions (Section 4) to push a stream of updates, without needing any complex OT/CRDT machinery. However, if an implementation combines these extensions together, it generalizes HTTP into a full synchronization protocol, and ReST into a synchronization architecture: HTTP: Hypertext *Transfer* Protocol can become: State *Synchronization* Protocol ReST: Representational State *Transfer* can become: Representational State *Synchronization* This allows an arbitrary set of clients and servers to make arbitrary edits to arbitrary resources, under arbitrary network delays and paritions, and merge all edits consistently, receiving updates as soon as they reconnect. This enables caches to support dynamic content, web applications to feature an offline mode, and textareas to support collaborative editing. 2. Versioning for Resources Each Braid resource has a current version, and a version history. Versions are specified as a set of one or more strings (called "version IDs") in the [RFC8941] format. Each version ID must be unique, to differentiate distinct changes at distinct points in time. To specify the version of content in a request or response body, a Version header MAY be included in a request for a PUT, PATCH or POST, or in the response to a GET: Version: "dkn7ov2vwg" Parallel edits can merge into a single version with multiple IDs: Version: "dkn7ov2vwg", "v2vwgdkn7o" Every version also has a set of parents, denoting the version(s) immediately before the version, that it derives from. The full graph of parents forms a Directed Acyclic Graph (DAG), representing the partial order of all versions. A version A is known to have occurred before a version B if and only if A is an ancestor of B in the partial order. Parents are specified with a header in a PUT request or GET response: Parents: "ajtva12kid", "cmdpvkpll2" For any two versions A and B that are specified in a Version or Parents header, A cannot be a descendent of B or vice versa. The ordering of versions in the list carries no meaning. If a client or server does not specify a Version for a resource it transfers, the recipient MAY generate and assign it new version IDs. If a client or server does not specify a Parents header when transferring a new version, the recipient MAY presume that the most recent versions it has seen are the parents of the new version. 2.1. Comparison with ETag The Version header is similar to an ETag, but has two differences: 1. ETags are sensitive to Content-Encoding. If you send the same version with a GZip Content-Encoding, it will have a different ETag, but the same Version. 2. A Version marks a unique point in time -- not unique content. If a resource is changed from version A to B, and then to C, such that the contents at A are the same as the contents at C, then it is possible versions A and C to have the same ETag, even though they have different Versions. This can break a CRDT or OT merge algorithm. Versions can be used in a variety of requests, as we explain next. 2.2. PUT a new version When a PUT request changes the state of a resource, it can specify the new version of the resource, the parent version IDs that existed when it was created, and the way multiple simultaneous changes should be merged (the "Merge-Type"): Request: PUT /chat Version: "ej4lhb9z78" | Update Parents: "oakwn5b8qh", "uc9zwhw7mf" | Content-Type: application/json | Merge-Type: sync9 | Content-Length: 64 | | [{"text": "Hi, everyone!", | | Snapshot "author": {"link": "/user/tommy"}}] | | Response: HTTP/1.1 200 OK Merge-Types are specified in [MERGE-TYPES]. The Version and Parents headers are optional. If Version is omitted, the recipient may assign new version IDs. If Parents is omitted, the recipient may assume that its current version is the version's parents. We call the set of data that updates a resource from one version to another an "update". An update consists of a set of headers and a body. In this example, the update includes a snapshot of the entire new value of the resource. However, one can also specify the update as a set of patches. 2.3. GET a specific version A server can allow clients to request historical versions of a resource in GET requests by responding to the Version and Parents headers. A client can specify a specific version that it wants with the Version header: Request: GET /chat Version: "ej4lhb9z78" Response: HTTP/1.1 200 OK Version: "ej4lhb9z78" | Update Parents: "oakwn5b8qh", "uc9zwhw7mf" | Content-Type: application/json | Merge-Type: sync9 | Content-Length: 64 | | [{"text": "Hi, everyone!", | | Snapshot "author": {"link": "/user/tommy"}}] | | 2.4. GET a range of historical versions A client can request a range of history by including a Parents and a Version header together. The Parents marks the beginning of the range (the oldest versions) and the Version marks the end of the range (the newest versions) that it requests. Request: GET /chat Version: "3" Parents: "1a", "1b" Response: HTTP/1.1 200 OK Version: "2" Parents: "1a", "1b" Version: "2" | Update Parents: "1a", "1b" | Content-Type: application/json | Merge-Type: sync9 | Content-Length: 64 | | [{"text": "Hi, everyone!", | | Snapshot "author": {"link": "/user/tommy"}}] | | Version: "3" | Update Parents: "2" | Content-Type: application/json | Merge-Type: sync9 | Content-Length: 117 | | [{"text": "Hi, everyone!", | | Snapshot "author": {"link": "/user/tommy"}} | | {"text": "Yo!", | | "author": {"link": "/user/yobot"}] | | To express a range of updates, the response body contains a sequence of updates; each with its own content-length. The format of this sequence is defined in the upcoming (Section 4.2) on Subscriptions. 2.5. Rules for Version and Parents headers If a GET request contains a Version header: - The Subscribe header (Section 3) MUST be absent. - The server SHOULD return a single response, containing that version of the resource in its body, with the Version header set to the version requested by the client. - If the server does not support historical versions, it MAY ignore the Version header and respond as usual, but MUST NOT include the Version header in its response. If a GET request contains a Parents header: - If the request does not also contain a Version, then the request MUST also contain a Subscribe header, and the server SHOULD send a set of versions updating the Parents to the current Version, and then subscribe the client to future updates. - If the server does not support historical versions, then it MAY ignore the Parents header, but MUST NOT include the Parents header in its response. If a GET request contains both a Version and Parents header: - The server SHOULD respond with a set of updates from the specified Parents to the specified Version. A server MAY refactor or rebase the version history that it provides to a client, so long as it does not affect the resulting state, or the result of the patch-type's merges. A server does not need to honor historical version requests for all documents, for all history. If a server no longer has the historical context needed to honor a request, it may respond using an error code that will be defined in a subsequent version of this draft. Request: GET /chat Version: "ej4lhb9z78" Response: HTTP/1.1 XXX Version: "ej4lhb9z78" 3. Updates can be expressed as Patches or Snapshots Whereas today's HTTP sends the current version of a resource as a "snapshot" in the body of a GET response, or a PUT request, and additionally allows clients to send a patch in a PATCH request, a full state synchronization protocol also needs to allow patches to be sent from server to client, within subscriptions and requests for history. This section describes a general form for updates that can be sent both client->server or server->client. Updates can be sent as snapshots or patches. When sent as patches, a single update can contain a single patch, or multiple patches. Unlike the PATCH method, these updates can be sent with idempotence when versioning information is included -- a client or server that receives the same update twice, for the same version, can discard the second update, and thus maintain idempotence. There are two reasons to send an update as a patch: o Patches are smaller and more efficient o Patches articulate *how* changes occur, which enables Merge-Types to intelligently merge, e.g. in collaborative editing. There are two types of patches: o Custom patch-types: As defined in HTTP PATCH [RFC5789] method, a custom patch type can be specified as a Content-Type. Any such patch can included in an update, by adding a Content-Type header to the udpate. o Range Patches: If a Content-Range header is specified on the update or patch, then it defines the region of the document that is being replaced by the content, as specified in [RANGE-PATCH]. Every patch MUST include either a Content-Type or a Content-Range. 3.1. PUT an update as a patch A Partial PUT [RFC9110] can express a patch with a Content-Range header: Request: PUT /chat Version: "g09ur8z74r" | Update Parents: "ej4lhb9z78" | Content-Type: application/json | Merge-Type: sync9 | Content-Length: 53 | | Patch Content-Range: json .messages[1:1] | | | | [{"text": "Yo!", | | "author": {"link": "/user/yobot"}] | | Response: HTTP/1.1 200 OK 3.2. GET an update as a patch A GET response can also express a patch, using Content-Range: Request: GET /chat Version: "g09ur8z74r" | Update Parents: "ej4lhb9z78" | Response: HTTP/1.1 200 OK Content-Type: application/json | Merge-Type: sync9 | Content-Length: 53 | | Patch Content-Range: json .messages[1:1] | | | | [{"text": "Yo!", | | "author": {"link": "/user/yobot"}] | | 3.3. PUT an update as a set of patches To format an update as a set of patches, include a header called "Patches" and assign it to the number of patches included, and format those patches in the body as a sequence separated by blank lines: Request: PUT /chat Version: "g09ur8z74r" | Update Parents: "ej4lhb9z78" | Content-Length: 189 | Content-Type: application/json | Merge-Type: sync9 | Patches: 2 | | Content-Length: 53 | | Patch Content-Range: json .messages[1:1] | | | | [{"text": "Yo!", | | "author": {"link": "/user/yobot"}] | | | Content-Length: 40 | | Patch Content-Range: json .latest_change | | | | {"type": "date", "value": 1573952202370} | | Response: HTTP/1.1 200 OK To distinguish the boundaries between patches in an update, each patch MUST include the following header: Content-Length: N This length determines where each patch ends, and next begins. 3.4. PUT an update as a custom patch-type Since PATCH is not idempotent, a client may want to send a patch idempotently using a PUT. The client SHOULD include a Version and Parents header to ensure idempotency. The server can then discard duplicate patches that it has already received. Request: PUT /chat Version: "up12vyc5ib" | Update Parents: "2bcbi84nsp" | Content-Length: 371 | Merge-Type: sync9 | Patches: 1 | | Content-Length: 288 | | Patch Content-Type: application/json-patch+json | | | | [ | | {"op": "test", "path": "/a/b/c", "value": "foo"}, | | {"op": "remove", "path": "/a/b/c"}, | | {"op": "add", "path": "/a/b/c", "value": []}, | | {"op": "replace", "path": "/a/b/c", "value": 42}, | | {"op": "move", "from": "/a/b", "path": "/a/d"}, | | {"op": "copy", "from": "/a/d", "path": "/a/d/e"} | | ] | | Response: HTTP/1.1 200 OK 4. Subscriptions for GET If a GET request includes the Subscribe header, the server can return a stream of updates; one for each new version. Each update can express the new content either as a snapshot, or a set of Patches. Request: GET /chat Subscribe: Response: HTTP/1.1 209 Subscription Subscribe: Version: "ej4lhb9z78" | Update Parents: "oakwn5b8qh", "uc9zwhw7mf" | Content-Type: application/json | Merge-Type: sync9 | Content-Length: 64 | | [{"text": "Hi, everyone!", | | Snapshot "author": {"link": "/user/tommy"}}] | | Version: "g09ur8z74r" | Update Parents: "ej4lhb9z78" | Content-Type: application/json | Merge-Type: sync9 | Patches: 1 | | Content-Length: 53 | | Patch Content-Range: json .messages[1:1] | | | | [{"text": "Yo!", | | "author": {"link": "/user/yobot"}] | | Version: "2bcbi84nsp" | Update Parents: "g09ur8z74r" | Content-Type: application/json | Merge-Type: sync9 | Patches: 1 | | Content-Length: 58 | | Patch Content-Range: json .messages[2:2] | | | | [{"text": "Hi, Tommy!", | | "author": {"link": "/user/sal"}}] | | Version: "up12vyc5ib" | Update Parents: "2bcbi84nsp" | Content-Type: application/json | Merge-Type: sync9 | Patches: 1 | | Content-Length: 288 | | Patch Content-Type: application/json-patch+json | | | | [ | | {"op": "test", "path": "/a/b/c", "value": "foo"}, | | {"op": "remove", "path": "/a/b/c"}, | | {"op": "add", "path": "/a/b/c", "value": []}, | | {"op": "replace", "path": "/a/b/c", "value": 42}, | | {"op": "move", "from": "/a/b", "path": "/a/d"}, | | {"op": "copy", "from": "/a/d", "path": "/a/d/e"} | | ] | | 4.1. Creating a Subscription A client requests a subscription by issuing a GET request with a Subscribe header: Subscribe: may be blank, set to "true", or contain arbitrary data, and is reserved for future use. This header modifies the normal GET method's semantics, to request a subscription to future updates to the data, rather than only returning the current version of the representation data. A server implementing Subscribe MUST include a Subscribe header in its response. The server then SHOULD keep the connection open, and send updates over it. In general, a server that implements subscriptions promises to keep its subscribed clients up-to-date by sending changes until the connection is closed. Once closed, a subscription can be resumed by the client issuing a subsequent GET request on the same document. 4.2. Sending multiple updates per GET To send multiple updates, a server concatenates multiple updates into a single response body. Each update MUST include headers and a body, and MUST specify the end of its body by including at least one of the following headers: - Content-Length: N - Patches: N The body may be zero-length. A server MAY separate each update with one or more blank lines. These lines do not count towards Content-Length. They can by used to visually separate updates, or to guide the behavior of certain proxies or clients: 1. Certain clients or proxies close inactive connections. A server signal that a connection is still active by periodically sending additional blank lines between updates. 2. Some clients (e.g. Firefox) only flush incoming data after a receiving a chunk of a certain size. A server can ensure small updates get flushed by padding them with blank lines. 4.3. Continuing a Subscription Once closed, a Braid subscription may be restarted by the client issuing a new subscription request. When the client reconnects, it may specify its last known version using the Parents header. The server SHOULD then send only the updates since that version. Example: Initial request: GET /chat Subscribe: Initial response: HTTP/1.1 209 Subscription Subscribe: Version: "ej4lhb9z78" | Update Content-Type: application/json | Content-Length: 64 | | [{"text": "Hi, everyone!", | | Snapshot "author": {"link": "/user/tommy"}}] | | Reconnection request: GET /chat Subscribe: Parents: "ej4lhb9z78" Reconnection response: HTTP/1.1 209 Subscription Subscribe: Version: "g09ur8z74r" | Update Parents: "ej4lhb9z78" | Content-Type: application/json | Merge-Type: sync9 | Patches: 1 | | Content-Length: 53 | | Patch Content-Range: json .messages[1:1] | | | | [{"text": "Yo!", | | "author": {"link": "/user/yobot"}] | | 4.4. Signaling "all caught up" When starting or resuming a subscription, the server can indicate which version is current by specifying a "Current-Version" header before starting the stream of versions. This should contain the frontier of time -- the leaves of the currently-known time DAG. The client can use this information to determine when it has caught up with the server's version at the time it received the client's request. Request: GET /chat Subscribe: Response: HTTP/1.1 209 Subscription Subscribe: Current-Version: "ej4lhb9z78" <-- Current Version Version: "b9z78ej4lh" | Updates Content-Type: application/json | Merge-Type: sync9 | Content-Length: 2 | | [] | | Version: "ej4lhb9z78" | <-- Current Version Parents: "b9z78ej4lh" | Content-Type: application/json | Merge-Type: sync9 | Content-Length: 64 | | [{"text": "Hi, everyone!", | "author": {"link": "/user/tommy"}}] V <-- Now caught up 4.5. Errors If a server has dropped the history that a client requests, the server can return a 410 GONE response, to tell the client "sorry, I don't have the history necessary to synchronize with you." 5. Design Goals This spec is designed to be: 1. Backwards-compatible with existing HTTP 2. Easy to implement simple synchronizers with. For instance, it should be easy to write a read-only synchronizer for an append-only log. 3. Possible to implement arbitrary synchronization algorithms. For instance, these extensions support any Operational Transform or CRDT algorithm. 6. Use Cases 6.1. Dynamic Resources: Animating a PNG Braid allows resources to become inherently dynamic -- able to change over time. You can use this to make a resource animate. In this example, a server streams changes to a PNG file in a sequence of patches. When the client renders the new state of the PNG after each patch, a new frame of animation is displayed. Request: GET /animated-braid.png Subscribe Response: HTTP/1.1 209 Subscribe Subscribe Content-Type: image/png | Update Content-Length: 170763 | | | | Snapshot Content-Type: image/png | Update Patches: 2 | | Content-Length: 1239 | | Patch Content-Range: bytes 100-200 | | | | | | | Content-Length: 62638 | | Patch Content-Range: bytes 348-887 | | | | | | 6.2. Dynamic Proxies and Caches Since updates aren't pushed, today's web often uses timeouts to trigger a cache becoming stale. Unfortunately, sometimes the timeout is wrong, and caches become out-of-date, and we have to wait for an unknown cache to timeout before we can see the new version of something. As a result, programmers have learned to force-reload pages habitually, and caches become less efficient than necessary. A cache supporting the Braid extensions, however, will automatically update whenever a change occurs. If a client starts a GET Subscription with a proxy, the proxy will then start and maintain a GET Subscription with the origin server. The origin server will promise to send the proxy updates over its GET Subscription, and the proxy will then relay these changes to all connected clients. If a set of clients and servers all support Braid, they will never need to force-reload caches for any data amongst them. 6.3. A Serverless Chat Example A Braid web application can operate offline. A user can use the app from an airplane, and their edits can synchronize when they regain internet connections. Additionally, the Braid protocol can be expressed over peer-to-peer transports (e.g. WebRTC) to support a a a a peer-to-peer synchronization without a server. For example, a chat application might be served and synchronized on Braid-HTTP, while also establishing redundant peer-to-peer connections on WebRTC, and translating all Braid-HTTP messages over the WebRTC connections, and vice versa. The server could then be shut down, and users of the chat app could continue to send messages to one another. Imagine the server serves the current set of trusted clients' IP addresses at the /peers state. Each client then subscribes to the /peers state with: GET /peers Subscribe: ------- [ {ip: '13.55.32.158', pubkey: 'x371...8382'}, {ip: '244.38.55.83', pubkey: 'o2u8...2s73'}, ... ] Each peer can then choose a set of those peers with whom to establish a WebRTC connection. It will then exchange Braid messages with those peers over that connection. 7. Related Work 7.1. Existing IETF Standards A number of IETF specifications already standardize aspects of synchronization for specific domains. IMAP [RFC9051] provides synchronization of email. WebDAV provides the synchronization of "collections" [RFC6578], and has been extended specifically for calendar data in CalDAV [RFC4791], and vCards in [RFC6350]. More recently, JMAP [RFC8620] provides an updated method of synchronization, supporting mail, calendars, and contacts. 7.2. IETF Work in Progress We wish to integrate this work with the excellent related efforts already underway: Resumable Uploads [draft-ietf-httpbis-resumable-upload] can also be expressed as a sequence of patches, from client to server. Each patch can specify a version in an "uploading" branch of time. Once the upload is complete, the branch can be "merged" back into the main version history. A subsequent version of this draft will show an example. Byte-Range-Patch [draft-wright-http-patch-byterange] also enables general patches using Content-Range. These efforts share our goals. 7.3. Web Frameworks Web applications typically synchronize the state of a client and server with layers of models, views, and controllers in web frameworks. By automating synchronization within HTTP, programmers have to write fewer layers of code on top of it. ====== Legacy Websites ====== ====== Braid Websites ====== Today's webpages are Braid generalizes HTTP generated from multiple into a standard for layers of state. Each layer synchronizing state within has a different API. and between websites. x Non-standard state API o Standard state API _Client__ / \ : o o o o : Webpage DOM o o o o State : \| \| : \| \| : x x : HTML Templates o o State : /| /| : /| /| : x x x x : JS Models o o o o State \ | | | | / | | | | | | | | | | | | o o o o - http:// - o o o o - http:// - / | | | | \ | | | | : x x x x : Views o o o o State : | \| | : | \| | : x x x : Controllers o o o State : \ / \| : \ / \| : x x : Models o o State : \ / : \ / \.... x ../ Database o State Server Today's programmers have to Each piece of Braid state (o) learn each API, and wire them has a URL; whether public or together, making sure that internal. State can be a changes to shared state function of other state, and synchronize across all and automatically recompute layers and computers. when its dependencies change. Braid guarantees network synchronization. 8. IANA Considerations 8.1. Header Field Registration HTTP header fields are registered within the "Message Headers" registry maintained at . This document defines the following HTTP header fields, so their associated registry entries have been updated according to the permanent registrations below (see [BCP90]): +---------------------+----------+--------------+-------------+ | Header Field Name | Protocol | Status | Reference | +---------------------+----------+--------------+-------------+ | Version | http | experimental | Section 2 | | Parents | http | experimental | Section 2 | | Merge-Type | http | experimental | Section 2.2 | | Patches | http | experimental | Section 2.3 | | Subscribe | http | experimental | Section 4 | | Current-Version | http | experimental | Section 3.4 | +---------------------+----------+--------------+-------------+ The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force". 9. Security Considerations XXX Todo 10. Conventions 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]. 11. Copyright Notice Copyright (c) 2023 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 (http://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. 12. References 12.1. Normative References [RFC5789] "PATCH Method for HTTP", RFC 5789. [RFC9110] "HTTP Semantics", RFC 9110. [RFC9111] "HTTP Caching", RFC 9111. [RFC9112] "HTTP/1.1", RFC 9112. [RFC8941] "Structured Field Values for HTTP" [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [MERGE-TYPES] draft-toomim-httpbis-merge-types-00 [RANGE-PATCH] draft-toomim-httpbis-range-patch-00 12.2. Informative References [XHR] Van Kestern, A., Aubourg, J., Song, J., and R. M. Steen, H. "XMLHttpRequest", September 2019. [SSE] Hickson, I. "Server-Sent Events", W3C Recommendation, February 2015. [REST] Fielding, R. "Architectural Styles and the Design of Network-based Software Architectures" Doctoral dissertation, University of California, Irvine, 2000. [RFC9051] Melnikov, Ed., Leiba, Ed., "Internet Message Access Protocol - Version 4rev2", RFC 9051, DOI 10.17487/RFC9051, August 2021, . [RFC6578] Daboo, C., Quillaud, A., "Collection Synchronization for Web Distributed Authoring and Versioning (WebDAV)", RFC 6578, DOI 10.17487/RFC6578, March 2012, . [RFC4791] Daboo, C., Desruisseaux, B., Dusseault, L., "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791, DOI 10.17487/RFC4791, March 2007, . [RFC6350] Perreault, S., "vCard Format Specification", RFC 6350, DOI 10.17487/RFC6350, August 2011, . [RFC8620] Jenkins, N., Newman, C., "The JSON Meta Application Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620, July 2019, . [RFC6902] Bryan, P., Nottingham, M., "Javascript Object Notation (JSON) Patch", RFC 6902. [RFC9110] Fielding, R., Nottingham, M., Reschke, J., "HTTP Semantics", RFC 9110 [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004. 13. Acknowledgements In addition to the authors, this spec contains intellectual contributions from the following people: - Mitar Milutinovic - Sarah Allen - Duane Johnson - Travis Kriplean - Marius Nita - Paul Pham - Morgan Dixon - Karthik Palaniappan We thank the following people for key feedback on previous drafts: - Austin Wright - Martin Thomson - Eric Kinnear - Olli Vanhoja - Julian Reschke - Chris Lemmons - Rahul Gupta We also thank Mark Nottingham, Fred Baker, Adam Roach, and Barry Leiba for facilitating a productive environment within the IETF. 14. Authors' Addresses For more information, the authors of this document are best contacted via Internet mail: Michael Toomim Invisible College, Berkeley 2053 Berkeley Way Berkeley, CA 94704 EMail: toomim@gmail.com Web: https://invisible.college/@toomim Greg Little Invisible College, Berkeley 2053 Berkeley Way Berkeley, CA 94704 EMail: glittle@gmail.com Web: https://glittle.org/ Rafie Walker Bard College EMail: slickytail.mc@gmail.com Bryn Bellomy Invisible College, Berkeley 2053 Berkeley Way Berkeley, CA 94704 EMail: bryn@signals.io Web: https://invisible.college/@bryn Joseph Gentle Invisible College, Berkeley 2053 Berkeley Way Berkeley, CA 94704 EMail: me@josephg.com Web: https://josephg.com/