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Bot Framework -- Cards

Abstract

The Bot Framework Card schema is an application-level representation of interactive cards for use within chat and other applications. The schema includes provisions for controlling the content, layout, and interactive elements of a card.

This schema is used within the Bot Framework Activity schema and is implemented by Microsoft chat systems and by interoperable bots and clients from many sources.

Table of Contents

  1. Introduction
  2. Card structure
  3. Basic cards
  4. Media cards
  5. Animation card
  6. Audio card
  7. Video card
  8. Receipt card
  9. Signin card
  10. Complex types
  11. References

Introduction

Overview

The Bot Framework Card schema provides a mechanism for transmitting content, layout information, and interactive elements within an interactive card. This specification does not describe the final visual form of a card, but the structure of the card suggests a layout without prescribing particular visual styles.

These cards are typically presented as attachments within the Bot Framework Activity schema, which in turn is typically transmitted within the Bot Framework Protocol [1], [2].

Bot Framework cards are each oriented around a particular kind of content (e.g. thumbnail images, transaction receipts) but use a shared set of features and conventions. These cards are designed to be rendered within interfaces that do not have full fidelity or interactive elements; in these cases, this specification provides guidance on how to predictably and gracefully reduce the complexity of each card to preserve the intent of the original item.

Relationship with Adaptive Cards

The Bot Framework Card schema was developed in conjunction with the v3 Bot Framework protocol. After Bot Framework v3 was released, a new effort to supplant Bot Framework cards with cross-application, generic cards resulted in the Adaptive Card [3] schema. Adaptive Cards provide a content-neutral format for data layout, in contrast to the content-specific Bot Framework cards.

Adaptive Cards are the recommended choice for new card content where supported. This is true even when a specific Bot Framework card exists.

Bot Framework cards are available where Adaptive Cards are not supported, and will be supported for existing users of the format until further announcements are made.

Requirements

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [4].

An implementation is not compliant if it fails to satisfy one or more of the MUST or REQUIRED level requirements for the protocols it implements. An implementation that satisfies all the MUST or REQUIRED level and all the SHOULD level requirements for its protocols is said to be "unconditionally compliant"; one that satisfies all the MUST level requirements but not all the SHOULD level requirements for its protocols is said to be "conditionally compliant."

Numbered requirements

Lines beginning with markers of the form CXXXX are specific requirements designed to be referenced by number in discussion outside of this document. They do not carry any more or less weight than normative statements made outside of CXXXX lines.

C1000: Editors of this specification MAY add new CXXXX requirements. They SHOULD find numeric CXXXX values that preserve the document's flow.

C1001: Editors MUST NOT renumber existing CXXXX requirements.

C1002: Editors MAY delete or revise CXXXX requirements. If revised, editors SHOULD retain the existing CXXXX value if the topic of the requirement remains largely intact.

C1003: Editors SHOULD NOT reuse retired CXXXX values. A list of deleted values MAY be maintained at the end of this document.

Terminology

activity

An action expressed by a bot, a channel, or a client that conforms to the Activity schema.

card

A Bot Framework card that adheres to this specification

channel

Software that sends and receives activities, and transforms them to and from chat or application behaviors. Channels are the authoritative store for activity data.

bot

Software that sends and receives activities, and generates automated, semi-automated, or entirely manual responses. Bots have endpoints that are registered with channels.

client

Software that sends and receives activities, typically on behalf of human users. Clients do not have endpoints.

sender

Software transmitting an activity.

receiver

Software accepting an activity.

field

A named value within an activity or nested object.

Card structure

This section defines the requirements for the basic structure of each card.

Cards include a flat list of name/value pairs, called fields. Fields may be primitive types. JSON is used as the common interchange format and although not all cards must be serialized to JSON at all times, they must be serializable to it. This allows implementations to rely on a simple set of conventions for handling known and unknown activity fields.

C2001: Cards MUST be serializable to the JSON format, including adherence to e.g. field uniqueness constraints.

C2002: Receivers MAY allow improperly-cased field names, although this is not required. Receivers MAY reject cards that do not include fields with the proper casing.

C2003: Receivers MAY reject cards that contain field values whose types do not match the value types described in this specification.

C2004: Unless otherwise noted, senders SHOULD NOT include empty string values for string fields.

C2005: Unless otherwise noted, senders MAY include additional fields within the card or any nested complex objects. Receivers MUST accept fields they do not understand.

Content-type

Cards are identified by a MIME-compatible [5] content-type. These content-types are not specified within the card itself; instead, these values accompany the card payload. In the Bot Framework Activity [1] schema, cards are included within attachments alongside the corresponding (contentType)[BotFramework-Activity.md#Content-type] field.

Transformations and display

Displaying a card within a client user interface frequently requires the implementer to make specific decisions about how to order and constrain content to match the visual style of the enclosing design. Further, this specification anticipates that these limitations are largely unavoidable and aims to assist implementers in choosing a path that makes graceful degradation of functionality possible.

This section provides guidance on which transformations best achieve the goal of preserving the intent of the card.

C3000: A Channel's card transformations and display MUST account for all known Bot Framework card types and include best-effort transformations into formats suitable for display to users.

C3002: Channels SHOULD preserve the ordering of text-bearing content fields as presented within this specification. Channels SHOULD NOT change the displayed format of the card based on how the fields appear in a payload transmitted by a sender.

C3003: Channels MAY alter the position of non-text multimedia content within the card in relation to text-bearing fields in order to achieve visual layout goals. Channels SHOULD preserve the order of non-text multimedia content as presented within the specification.

The C3003 requirement is intended to allow repositioning of e.g. an image below or above a card title to match visual style within the channel.

C3004: Channels SHOULD preserve all content within the card.

C3005: Channels MAY establish rules requiring specific fields within card types.

Channels are recommended to make these rules simple.

C3006: Unless otherwise noted in this specification or in accordance with C3004, all card fields are optional.

Buttons

All cards include content (in the form of one or more fields) and an array of buttons, each of which is represented by an action. Some cards include an additional card action, the "tap action," describing the behavior when the user taps the card but not any of the buttons.

All Bot Framework card types except Adaptive Cards include a buttons field, which contains zero or more buttons to be presented to a user. The type of the buttons field is an array of type cardAction, defined in the Bot Framework Activity schema [1].

C4000: Channels MAY define a minimum and maximum number of buttons to allow on each card type.

Channels are recommended to use simple values for the minimum and maximum number of buttons and avoid complex formulas, such as changing the total number of buttons based on whether certain kinds of content are used.

C4001: Channels MUST NOT change the order of buttons on a card.

C4002: If a bot sends a button with action type not supported by the channel, the channel SHOULD preserve the button but provide a degraded experience.

The best degraded experience is an interactive dialog that, upon being clicked, tells the user that the bot sent an action that is not supported. If this is not possible, showing a disabled button is preferred. If this is not possible, the button should be dropped, taking care that the order of other buttons not be changed per C4001.

C4004: If a bot sends fewer than the minimum or more than the maximum number of buttons allowed on a card, the channel MAY drop the card. Alternatively, the channel MAY down-render the card using rules described for that card type.

Basic cards

Bot Framework defines two cards for presenting a mix of image, text, and interactive elements:

Both basic cards support a shared set of properties and generally have card-specific layout.

Basic card title

The title field contains the title of the card. The value of the title field is of type string.

Basic card subtitle

The subtitle field contains the subtitle of the card. The value of the subtitle field is of type string.

Basic card text

The text field contains the text of the card. The value of the text field is of type string.

Basic card images

The images field contains one or more images to be shown within the card. The value of the images field is an array of type cardImage.

C5400: If a bot sends more than the maximum number of images allowed on a card, the channel SHOULD drop excess images.

C5401: If a bot sends fewer than the minimum or more than the maximum number of images allowed on a card, the channel MAY drop the card.

Basic card buttons

The buttons field is described in detail in the above section titled Buttons.

Basic card tap

The tap field contains an action that may be activated when a user clicks on a non-button or otherwise non-interactive part of a card. The value of the tap field is of type cardAction.

C5500: Channels that do not support interactive image actions SHOULD drop the tap field while preserving the containing card.

Media cards

Bot Framework defines three kinds of cards designed expressly to transmit rich media content:

All media cards support a shared set of properties and have card-specific behaviors.

C6000: Channels that can display media card content SHOULD document which formats are supported and corresponding limitations (minimum/maximum bitrate, resolution, etc.).

C6001: Channels SHOULD use HTTP content-type when retrieving the media to establish its actual type.

C6002: A channel that receives media card content of an unsupported type MAY send a hyperlink to the media to the user.

Media card title

The title field contains the title of the card. The value of the title field is of type string.

Media card subtitle

The subtitle field contains the subtitle of the card. The value of the subtitle field is of type string.

Media card image

The image field contains a placeholder image to be used in place of the media. The value of the image field is a complex object of type thumbnailUrl.

Media card media

The media field contains one or more alternative formats of the same media to be presented. The value of the media field is an array of complex objects of type 'mediaUrl'.

C6401: If a receiver receives multiple objects within the media array, it MAY prefer media whose profile field it understands.

C6402: If a receiver receives multiple objects within the media array and it does not understand the profile field of any, it SHOULD display the first object in the array.

Media card buttons

The buttons field is described in detail in the above section titled Buttons.

C6500: Senders SHOULD NOT include media transport control buttons (e.g., play/pause). These are intrinsic to the media playback window.

Media card shareable

The shareable field describes whether a client user experience should allow the user to share the content. The value of the shareable field is a boolean. If omitted, the default value is true.

C6600: Channels that do not have configurable settings for sharing content SHOULD ignore the value of the shareable field.

Media card autoloop

The autoloop field describes whether a client should automatically restart the media when it reaches the end of its content. The value of the autoloop field is a boolean. If omitted, the default value is true.

C6700: Channels that do not have configurable looping for content SHOULD ignore the value of the autoloop field.

Media card autostart

The autostart field describes whether a client should automatically start playing content when received. The value of the autostart field is a boolean. If omitted, the default value is true.

C6800: Channels SHOULD honor the value of the autostart if able and if doing so does not degrade a user's experience.

Media card aspect

The aspect field describes the visual aspect ratio of the media content. The value of the aspect field is a string with allowed values of 16:9 and 4:3. 16:9 corresponds to media with width-to-height ratio of 16 to 9; 4:3 corresponds to media with width-to-height ratio of 4 to 3. Any other values have undefined meaning.

This field is advisory in nature only. The media's actual aspect ratio should be determined by inspecting the media itself.

C6900: Senders SHOULD list an aspect value corresponding to the media linked in the media field.

C6901: If media of multiple aspect ratios is included in the media field, senders SHOULD include an aspect ratio for the first object in the array.

C6902: Senders MAY include aspect values for media that do not have visual aspect ratios (e.g., audio-only media) if the aspect field applies to the image field for the card.

C6903: Senders SHOULD NOT include aspect values if the media does not have a visual aspect ration and if no image field is supplied.

C6904: Senders SHOULD NOT include values other than 16:9 or 4:3 unless it has knowledge that the receiver supports it.

Media card duration

The duration field describes the length of the media content without requiring a receiver to open the content. The value of the duration field is a string in [ISO 8601 duration format]((https://www.iso.org/iso-8601-date-and-time-format.html) [7]).

C6920: Senders SHOULD only send values in the ISO 8601 Duration format. Senders SHOULD NOT send times or time intervals in the duration field.

C6930: Receivers SHOULD ignore duration fields they do not understand or which are in conflict with length encoded into the media.

Media card value

The value field contains a programmatic payload specific to this media card.

C6950: Senders SHOULD NOT include value fields of primitive types (e.g. string, int). value fields SHOULD be complex types or omitted.

Animation card

Animation cards contain animated image content. Typically this content does not contain sound, and is typically presented with minimal transport controls (e.g, pause/play) or no transport controls at all. Some channels treat animation and video content the same way.

Animation cards follow all shared rules defined for Media cards.

Animation cards are identified by a contentType value of application/vnd.microsoft.card.animation.

Audio card

Audio cards contain audio content.

Audio cards follow all shared rules defined for Media cards.

Audio cards are identified by a contentType value of application/vnd.microsoft.card.audio.

C7100: Senders SHOULD NOT send video content within audio cards.

C7101: If it receives video content within an audio card, a client MAY elect to present only the audio portion of the media.

Video card

Video cards contain video content. Typically this content is presented to the user with advanced transport controls (e.g. rewind/restart/pause/play). Some channels treat animation and video content the same way.

Video cards follow all shared rules defined for Media cards.

Video cards are identified by a contentType value of application/vnd.microsoft.card.video.

Receipt card

Receipt cards contain two tables of data (a list of receipt items, and a list of facts). They are intended to be an informative display and are not necessarily actionable on their own. For integration with payment systems suitable for conducting transactions, see the payment action.

Receipt cards are identified by a contentType value of application/vnd.microsoft.card.receipt.

C7300: Channels SHOULD render the items and facts fields as visual tables or approximations of tables (using e.g. fixed-width formatting).

C7301: Channels SHOULD render a delimiter between the items and facts field if both are present and contain any elements.

Receipt card title

The title field contains the title of the card. The value of the title field is of type string.

Receipt card items

The items field contains receipt items to be displayed in tabular form. The value of the items field is an array of type receiptItem.

C7310: Channels MUST NOT alter the order of items within the items array.

Receipt card facts

The facts field contains a flat list of key/value pairs to be displayed in tabular form. The value of the facts field is an array of type fact.

C7320: Channels MUST NOT alter the order of items within the facts array.

C7321: Channels SHOULD NOT reject the facts field or its contents if more than two items have the same key.

Although facts contains key-value pairs, receivers should not take the key-value pairing literally, and should allow duplicates per C7531.

Receipt card tap

The tap field contains an action that may be activated when a user clicks on a non-button or otherwise non-interactive part of a card. The value of the tap field is of type cardAction.

C7330: Channels that do not support interactive image actions SHOULD drop the tap field while preserving the containing card.

Receipt card total

The total field contains the total field to be displayed on the receipt. The value of the total field is a string.

Receipt card tax

The tax field contains the tax field to be displayed on the receipt. The value of the tax field is a string.

Receipt card VAT

The vat field contains the value-added tax (VAT) field to be displayed on the receipt. The value of the vat field is a string.

Receipt card buttons

The buttons field is described in detail in the above section titled Buttons.

Signin card

Signin cards are used to send a sign-in request to a user. Channels that support sign-in cards typically adorn the card with additional visual style to designate it as a sign-in card.

Signin cards are identified by a contentType value of application/vnd.microsoft.card.signin.

Signin card text

The text field contains the text of the card. The value of the text field is of type string.

Signin card buttons

The buttons field is described in detail in the above section titled Buttons.

Complex types

This section defines complex types used within the activity schema, described above.

Thumbnail URL

Some clients have the ability to display custom thumbnails for non-interactive attachments or as placeholders for interactive attachments. The thumbnailUrl field identifies the source for this thumbnail. Data URIs, as defined in RFC 2397 [6] are typically also allowed.

C8000: Receivers SHOULD accept HTTPS URLs.

C8001: Receivers MAY accept HTTP URLs.

C8002: Channels SHOULD accept data URIs.

C8003: Channels SHOULD NOT send thumbnailUrl fields to bots.

Card image

Card images are used to display image content within Hero cards and Thumbnail cards.

Card image URL

The url field references image content to be displayed within a card. Data URIs, as defined in RFC 2397 [6] are typically supported by channels. The value of the url field is of type string.

C8100: Channels SHOULD accept HTTPS URLs.

C8101: Channels MAY accept HTTP URLs.

C8102: Channels SHOULD accept data URIs.

Card image Alt tag

The alt field contains equivalent content for clients that cannot process images or have not yet loaded the image. The value of the alt field is a string.

Card image tap

The tap field contains an action to be activated if the user taps on an image or associated framing. The value of the tap field is of type cardAction.

C8120: Channels that do not support interactive image actions SHOULD drop the tap field while preserving the containing card image.

Media URL

A media URL object contains information about a media attachment.

Media URL URL

The url field contains a URL to the media. Because media URL objects do not contain content type information, data URIs, as defined in RFC 2397 [6, are not supported.

C8200: Receivers SHOULD accept HTTPS URLs.

C8201: Receivers MAY accept HTTP URLs.

C8202: Senders SHOULD NOT send data URIs.

Media URL profile

The profile field contains an optional hint to the client to allow it to differentiate between media URLs. The value of the profile field is of type string and is defined by the channel.

Receipt item

A receiptItem is a single row to be shown within the items field of a receipt card.

Receipt item title

The title field contains the title for the receipt item. The value of the title field is a string.

Receipt item subtitle

The subtitle field contains the subtitle for the receipt item. The value of the subtitle field is a string.

Receipt item text

The text field contains the text for the receipt item. The value of the text field is a string.

Receipt item image

The image field contains an image to be shown within the receipt item row. The value of the image field is an object of type cardImage.

Receipt item price

The price field contains the displayed unit price with accompanying currency symbols. The value of the price field is a string.

Receipt item quantity

The quantity field contains the quantity of units in the receipt row. The value of the quantity field is a string. If omitted, the implied value is 1.

Receipt item tap

The tap field contains an action that may be activated when a user clicks on a non-button or otherwise non-interactive part of a card. The value of the tap field is of type cardAction.

Fact

A fact is a single row to be shown within the facts field of a receipt card.

Fact key

The key field contains the nominative component of the fact. The value of the key field is a string.

Fact value

The value field contains the objective component of the fact. The value of the value field is a string.

References

  1. Bot Framework Activity
  2. Bot Framework Protocol
  3. Adaptive Cards
  4. RFC 2119
  5. MIME media types
  6. RFC 2397
  7. ISO 8601

Appendix I - Changes

2018-10-08 - dandris@microsoft.com

2018-07-05 - dandris@microsoft.com

  • Initial draft
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