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This specification defines methods for presentation of a text conversation with focus on the real-time features. The aim is to give the participants in a conversation a good opportunity to perceive the real-time flow of the conversation and also provide a display of the history of the conversation that makes it easy to read. Both two-party and multi-party situations are defined.
1.
Introduction
2.
Terminology
3.
Scope
4.
Real-time preview presentation method
4.1.
Entries in creation
4.2.
Completion of local entry
4.3.
Completion of preview entry
4.4.
Order of entries
4.5.
Scrolling and buffering
4.6.
Moving between different states
4.7.
En bloc transmission
4.8.
Auto-real-time for Emergency calls and Textphone calls
4.9.
Reasons to finish an entry
4.10.
Erasure
4.11.
Display formatting
5.
Transport and presentation considerations
6.
Multi-party sessions
7.
Presence indication
8.
Alerting
9.
IANA Considerations
10.
Security Considerations
11.
Normative References
§
Authors' Addresses
§
Intellectual Property and Copyright Statements
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This is a specification of methods for presentation of a real-time text conversation. The aim is to give the participants in a conversation a good opportunity to perceive the real-time flow of the conversation and also provide a display of the history of the conversation that makes it easy to follow the flow. One reason to specify the presentation method is to be able to give participants a synchronized view of the conversation even if they use different presentation characteristics. The methods are intended for use in a protocol environment where text can be transmitted in real-time or in fragments of messages. Both two-party situations and multi-party session presentations are specified. The specification is mainly on the presentation level, relatively independent of the transport layer. It has though some requirements on the lower layers, as well as some characteristics of the lower layers cause slightly different user experience in the presentation.
The method is possible to use for two-party calls and multi-party calls. A two-party view is shown in Figure 1 (Two-party call with real-time preview.).
_________________________________________________
| |^|
| | |
| | |
| | |
| [Anne]Hi, Anne here. | |
| | |
| [Eve]Hi, this is Eve, calling from Paris. | |
| I thought you should be here. | |
| | |
| [Anne]I am coming on Thursday, | |
| my performance is not until Friday | |
| morning. | |
| [Anne]Can we meet on Thursday evening? | |
| | |
| [Eve]Yes, definitely. How about 7pm. | |
| at the entrance of the restaurant | |
| Le Lion Blanc? | |
| [Eve]we can have dinner and then take a walk| |
| |_|
| <Eve-typing> But I need to be back to the |_|
| hotel by 11 because I have t |v|
|_____________________________________________|_|
| OK, no prob |
| |
|_______________________________________________|
| Figure 1: Two-party call with real-time preview. |
Figure 1: The text is here displayed in a traditional chat view, with labelled entries from each participant ordered in a list with newest entry last. Older entries are scrolled up, out of the screen area when there is no room for them.
Real-time text arriving from other participants is displayed in 'preview areas' within the scrolling 'history' window. They are formatted to look different and are presented at the bottom of the history window until they are completed. When completed they move up in the history window and added to the history record. The text being entered by the local participant appears in a separate entry field that is preferably just below the history field (to minimize eye movements when reading and typing).
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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 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].
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This specification describes methods for presenting a text conversation so that the gradual entry of text is made visible to the users. One method has text flowing in real-time in a way that is similar to common text chat, but with the possibility to follow entries while they are created in a real-time preview area. The method may be applied on any text conversation transport method that transmits text on a character by character, time-sampled, word by word, or other small chunk basis. The methods cover both two-party and multi-party situations.
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The presentation method described here is intended to give a convenient view of a text conversation between two or more participants in a session. It is intended to be compatible with the requirements of ITU-T T.140 [1], and to look familiar for text chat users and be feasible to implement in terminals with small displays. The basic concept however could be implemented in other text technologies as well and displayed in different ways. ITU-T T.140 [1], Appendix I, describes a traditional chat view and a two-column view. The display formats shall be implemented so that terminals in a session can implement different display views meeting the requirements of T.140 [1] and giving the users a synchronized view of the flow of the conversation.
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Entries in creation SHALL be displayed in a real-time preview area, one for each participant for who is currently typing. The real-time preview areas MAY be placed under the list of completed entries as shown in Figure 1 and 2, or at any other suitable place in the user interface. If video from the participants is also displayed, then it MAY be suitable to display the real-time preview areas under the video image of the participant. The real-time text MAY also be displayed in a manner more closely associated with earlier exchanged text entries by the same participant (e.g. text from each participant goes in its own column).
If real-time preview from other participants are placed under the list of completed entries as in Figure 1 and 2, the text being entered by the local participant SHOULD be placed at the bottom in its own text entry field. This is recommended for a number of reasons. First, this is the only "editable" text on the screen. It also facilitates an optional input behavior where the local user may sometimes be holding their text back until it is completed while normally transmission occurs in real-time. Having the user input area be in a separate field MAY also be useful when scrolling the output field so that the input field always stays in view even as the history and text previews are scrolled out of view to read older text.
For ease of reading different entries, it is RECOMMENDED to place all entries close together in the display area.
During entry, the following actions MAY be requested:
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Text from the local participant SHALL be entered in the local user input field, until an end-of-entry event occurs. The end of entry event may be triggered by a send button, a RETURN or when another local user selectable "post what I have so far" condition is met ( such as pause in typing, a delimiting character such as full stop, or a turn-taking token). When an end-of-entry event occurs, the entry shall be finished by addition of a Line Separator, if no new line alternative (CR, CR LF, LF, New Line, Line Separator) was already included. The completed entry SHALL be moved to the history display area and an end-of-message indicator SHALL be transmitted If the protocol used has an end-of-message indicator defined.
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Text from the remote participants SHALL be entered in the preview area until an end-of entry event occurs. The end-of-entry is identified by any variant of a NEW LINE coded in the character set used, or an end of message indicator if there is a specific coding of that event. When an end-of-entry event occurs, the completed entry SHALL be moved to the history display area.
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The order of displayed entries in the display area SHALL be the timing order when the entries were "posted" to the display from the preview area. That is, when the new line or end-of-message indicator is received.
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When there are entries in the history field that are pushed (scrolled) out of the view by new text coming in, it SHOULD be possible to scroll them back within a practical limit. When the history field is scrolled, it SHALL stay in that scrolled position until scrolling is changed again or (optionally) a new entry is received. When scrolled to the bottom, the window SHALL auto-scroll to show new entries as well as old as they occur. When the display arrangement is made as in Figure1 and 2, the preview field and the history field SHOULD scroll together as one area.
The input field of the local participant SHOULD always be visible regardless of the scroll position of the History field.
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Entries can be either "real-time (preview)" or "historical" and they can be either "displayed" or "hidden". When real-time text is received it SHALL BE classified as a real-time entry until an end-of-entry indicator is received. Real-time entries SHOULD be displayed in the real-time preview field. Once an end-of-entry indicator is received, the entry SHALL become historical and SHOULD be move into the history display field. Its position within the history SHALL be determined by the time that its end-of-entry indicator was received.
The local user may select to hide either the entries while they are real-time (previews) or when they are historical. Hiding entries when they are in real-time state may be done to avoid distraction for the local participant. The feature to hide the entries while in real-time state SHOULD provide some alert when an end-of-entry indicator is received as well as when real-time text stops coming in for a period of time. (The alert due to pause in incoming text is important because some real-time text users are not accustomed to sending end of entry indications(e.g. RETURNs) or may use a text based end-of-entry indication (such as GA).
An entry (or category of entries) can be placed in a hidden state by user command to hide it (them). (e.g. Hide all but "Mary" to make it easier to see her thread)
The default SHALL be that both real-time and history are not hidden.
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It SHOULD be possible for the participants to hold their text and not have it sent to the other participants until after the end-of-message event occurs. This enables users who do not want their message to be viewed by other participants until they have verified it. This also facilitates editing since random editing can be done on the text block before it is sent. This also allows a block of text to be pasted into the text entry area and then edited before it is sent. This could be new text or a previous text entry that the user would like to resend with edits. The en bloc method SHALL NOT be the only method for sending. A 'real-time / block send' switch SHOULD be located near the local user's text entry field Real-time SHALL be the default method for sending but a user preference setting MAY change the default to en bloc.
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When it is detected that the session is used for emergency purposes, the text transmission SHALL be switched to real-time regardless of its previous setting.
When it is detected that the session is used for a connection with a PSTN textphone through a gateway, the text transmission SHOULD be switched to real-time regardless of its previous setting. The user SHOULD be given an indication on the situation that also may call for application of turn-taking habits and limitations in simultaneity of voice and text communication.
The user SHALL still be provided with a possibility to switch to en bloc sending after the session is established.
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The default end of entry action SHOULD be a new line request from the user.
A specific send button MAY also be used.
Other end of entry actions SHOULD also be used when operating in
real-time mode.
A list of such actions is:
Especially in PSTN text gateways having user input from PSTN text telephones, the following sequences SHOULD be included among those causing an entry to be finished:
White spaces (space bar, New line, CR, and LF) after those characters SHALL be accepted and included in the finished entry. (Some users do type a space character after the turn-taking indicator and some textphones will send return after the turn-taking symbol).
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Erasure SHALL only be done from the last character entered per participant. Erasure SHALL NOT be possible once entries have been moved into the history field.
Transmitted characters that take no position on the display (e.g. Bell or Alert in Session) SHALL not take any specific erasing action, but be regarded to be erased simultaneously with the succeeding character.
Characters that are composed by multiple keystrokes SHALL be erased by one erasing action.
New lines inserted by automatic line break and word wrap actions purely for display formatting purposes by the local system SHALL not require any specific erasing action.
When erasing, the erasing action MUST be performed strictly according to the rules above, in order to maintain a synchronized view of the conversation for the participants, even if conversation participants use different display formats, such as the two-panel mode described in ITU-T T.140 1 (ITU-T, “Recommendation T.140, Protocol for Multimedia Application Text Conversation (including Addendum),” February 2000.) [T140.refs] and the real-time preview mode described here.
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The display SHALL be word-wrapped within the limits of the window.
The labels on the entries SHOULD display the user name of the participant. If this information is not available, labels indicating "Received" and "Transmitted" or other suitable names for the participants SHOULD be used.
The following operations SHOULD be possible to do:
The real-time preview display area MAY follow the same display formatting regarding font size, colours etc as the display area or MAY be different.
Each real-time preview area MAY have a fixed or adjustable size. It MAY also have no specific scrolling features or its own scrolling mechanism..
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It is RECOMMENDED that characters be buffered and transmitted in 300
ms intervals on the transport level. It is permissible to buffer
characters for transmission in up to 500 ms intervals. Display of
received chunks of text SHOULD be done one character at a time spread
over the transmission interval so that adding a chunk of text to the
real-time preview window approximately covers the transmission interval
to give a smoother flow.
It SHOULD be possible
to select participants in a multi-party situation for whom text is
displayed, while text entries from others are hidden.
It SHOULD be possible to hide the real-time preview area for selected participants, but let text be displayed when entries are completed.
The presentation method MAY be used with
transport methods for real-time text and for all text message methods
where it is possible to use timer based transmission to transmit
fragments of message entries.
The method is designed in order to be usable for real-time text conversation with coding and presentation according to ITU-T T.140 including its amendment 1 (ITU-T, “Recommendation T.140, Protocol for Multimedia Application Text Conversation (including Addendum),” February 2000.) [T140.refs], and IETF RTP (Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, “RTP: A Transport Protocol for Real-Time Applications,” July 2003.) [RFC3550] transport with packetization as defined in RFC 4103 (Hellstrom, G. and P. Jones, “RTP Payload for Text Conversation,” June 2005.) [RFC4103]. These coding, presentation and transport specifications SHOULD be used whenever there is no strong reason to follow other specifications. The methods for applying this in a multi-party situation is described in IETF Text media handling in RTP based real-time and message conferences draft-hellstrom-text-conference (Hellstrom, G. and A. Wijk, “Text media handling in RTP based real-time conferences,” March 2010.) [I‑D.hellstrom‑text‑conference] .
An example of another environment where the real-time text with preview presentation is feasible, is with the messaging protocol IETF MSRP (Campbell, B., Mahy, R., and C. Jennings, “The Message Session Relay Protocol (MSRP),” September 2007.) [RFC4975], where the message fragment concept MAY be used for a real-time transmission and presentation according to the description in this specification.
The transport method SHALL allow identification of the source of text, so that text from different sources can be arranged for convenient and readable presentation at the receiving end. [e.g. to attach labels to the incoming text).
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A multi-party session can be presented in a similar manner as the two-party session. The chat-view with real-time entry at the bottom of the window is one possible view.
A three-party view is shown in this example .
_________________________________________________
| |^|
| | |
| | |
| | |
|[Alice]Hi, Alice here. | |
| | |
|[Bob]Bob as well. | |
| | |
|[Eve]Hi, this is Eve, calling from Paris. | |
| I thought you should be here. | |
| | |
|[Alice]I am coming on Thursday, my | |
| performance is not until Friday morning. | |
| | |
|[Bob]And I on Wednesday evening. | |
| | |
|[Alice9Can we meet on Thursday evening? | |
| | |
|[Eve]Yes, definitely. How about 7pm. | |
| at the entrance of the restaurant | |
| Le Lion Blanc? | |
|[Eve]we can have dinner and then take a walk | |
| | |
| <Eve-typing> But I need to be back to | |
| the hotel by 11 because I need | |
| |-|
| <Bob-typing> I wou |-|
|_____________________________________________|v|
| of course, I underst |
|_______________________________________________|
| Figure 2: Three-party call with real-time preview. |
Figure 2: This figure shows how a coordinated column view MAY be presented on Alice´s device.
______________________________________________________________________ | Bob | Eve | Alice | |____________________|______________________|________________________| | | |I will arrive by TGV. | |My flight is to Orly| |Convenient to the main | | |Hi all, can we plan |station. | | |for the seminar? | | |Eve, will you do | | | |your presentation on| | | |Friday? |Yes, Friday at 10. | | |Fine, wo | |We need to meet befo | |____________________________________________________________________|
Figure 3: A coordinated column-view of a three-party session with entries ordered in approximate time-order.
In the column view, the column showing text transmitted from the device where the presentation is made, SHOULD be placed to the right of all other columns, so that users recognize the operating environment between different devices.
In an environment with less space in the display it MAY be necessary to give up on displaying the relative time order in the column view in order to display more of the conversation contents in available space.
Yet other situations MAY call for display in separate windows for example underneath video images from each participant.
________________________ _____________________ ___________________ | Bob | | Eve | | Alice | |______________________| |___________________| |__________________| | ooooo | | 888 | | ... | | / o o\ | | 8/- -\8 | | ||||| | | ( _ | | | 0| | |0 | | || o o || | | \_____/ | | | _ | | | || v || | | | | \___/ | | ||\___/|| | |______________________| |___________________| |__________________| |Help me to spell | |necessary | |ne.... OK you take| |nessessarry,I always | | | |it | |get it wrong | | | | | |______________________| |___________________| |__________________|
Figure 4: Example of text conversation entries placed underneath video images from each participant.
When implemented in an environment that supports multi-party calls, it may be felt less important to maintain a real-time preview view of text from all participants. It may be very important for some participants to have rapid real-time preview presentation of selected participants, e.g. for live captioning of the call by a third party.
Thus it may be desirable to be able to turn on or off the preview presentation per user. When turning off real-time preview from one participant, its presentation SHALL disappear from the preview window, and text SHALL be entered en-bloc to the history display as they are finished for that participant.
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Appropriate SIP based presence features SHOULD be used to indicate status in the user interface, e.g. that the user is typing when in ‘en bloc’ mode.
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In order to be useful for hearing impaired, deaf and deaf-blind users
as well as all situations with all users, it is important to provide
audible, visual and, where possible, tactile alerting from events in the
text conversation application.
It should be
possible for a user to get external alerting signals with a method
preferred by the user. It may for example be vibration, light flashes or
sound as selected by the user. It should also be possible to get
alerting on the screen at certain events.
The
signals to external alerting systems should be issued when an incoming
request for session initiation is received. When the method is used in
connection with T.140 (ITU-T, “Recommendation T.140, Protocol for Multimedia Application Text Conversation (including Addendum),” February 2000.) [T140.refs] presentation, it
should also be issued when the alert-in-session T.140 control event is
received.
For minor events, for example when
an entry from a user is completed and displayed in the conversation
display area, an indication MAY be given e.g. by an on-screen flashing
or any other suitable alerting signal.
It may
be useful to provide external alerting also for these minor events in
specific situations. If the user has not touched the application for a
number of minutes when the minor event occurs it may be of interest to
get an external alert. Details of such arrangements are outside the
scope of this document.
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None.
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This specification does not introduce any procedures that change security issues from what is already specified for the session and transport environment where the presentation method is applied.
| TOC |
| [T140.refs] | ITU-T, “Recommendation T.140, Protocol for Multimedia Application Text Conversation (including Addendum),” February 2000. |
| [RFC4103] | Hellstrom, G. and P. Jones, “RTP Payload for Text Conversation,” RFC 4103, June 2005 (TXT). |
| [RFC3550] | Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, “RTP: A Transport Protocol for Real-Time Applications,” STD 64, RFC 3550, July 2003 (TXT, PS, PDF). |
| [RFC4975] | Campbell, B., Mahy, R., and C. Jennings, “The Message Session Relay Protocol (MSRP),” RFC 4975, September 2007 (TXT). |
| [RFC2119] | Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML). |
| [I-D.hellstrom-text-conference] | Hellstrom, G. and A. Wijk, “Text media handling in RTP based real-time conferences,” draft-hellstrom-text-conference-02 (work in progress), March 2010 (TXT). |
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| Gunnar Hellstrom | |
| Omnitor | |
| PO Box 92054 | |
| 12006 Stockholm | |
| Sweden | |
| Phone: | +46-8-58900050 |
| Email: | gunnar.hellstrom@omnitor.se |
| Norman Williams | |
| Gallaudet University | |
| 800 Florida Ave | |
| Kendall Hall 101a | |
| Washington, DC 20002 | |
| USA | |
| Email: | norman.williams@gallaudet.edu |
| Arnoud A. T. van Wijk | |
| Realtimetext.org | |
| Email: | arnoud@realtimetext.org |
| Gregg C. Vanderheiden | |
| Trace R&D Center, University of Wisconsin-Madison | |
| 1550 Engineering Drive | |
| Madison, WI 53706 | |
| USA | |
| Email: | gv@trace.wisc.edu |
| URI: | http://www.engr.wisc.edu/ie/faculty/vanderheiden_gregg.html |
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