rfc767.txt
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<pd> := <<ind>>
<<ind>> := name:"INDEPENDENT", <pe>
<pe> := name:"FACSIMILE", <facsimile structure>
name:"TEXT", <text structure>
or
proplist:(
name:"INDEPENDENT",
proplist:(
name:"FACSIMILE", <facsimile structure>
name:"TEXT", <text structure>
)endlist
)endlist
A Stream Example
By making use of the structure and the sequential ordering option
it is possible to initiate a stream. The stream will proceed at
its own pace until concluded.
<body> := <pd>
<pd> := <<seq>>
<<seq>> := name:"SEQUENTIAL", <pe>
<pe> := <pd>
<pd> := <<sim>>
<<sim>> := name:"SIMULTANEOUS", <pe>
<pe> := name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
Postel [Page 19]
August 1980
A Structured Format for Transmission of Multi-Media Documents
Specification
or
proplist:(
name:"SEQUENTIAL",
proplist:(
name:"SIMULTANEOUS",
proplist:(
name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
)endlist,
name:"SIMULTANEOUS",
proplist:(
name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
)endlist,
.
.
.
)endlist
)endlist
Such a document structure suggests a slide presentation.
Multiple Active Stream Example
This example is exotic but illustrates what is possible. By making
use of the structure and the simultaneous ordering it is possible
to start in parallel two or more separate streams. Each stream
will proceed at its own pace until all are concluded.
<body> := <pd>
<pd> := name:"SIMULTANEOUS", <pe>
<pe> = <pd>
<pd> := name:"SEQUENTIAL", <pe>
<pe> = <pd>
<pd> := name:"SIMULTANEOUS", <pe>
<pe> := name:"VOICE",
<voice structure>
name:"GRAPHICS",
<graphics structure>
[Page 20] Postel
August 1980
A Structured Format for Transmission of Multi-Media Documents
Specification
or
proplist:(
name:"SIMULTANEOUS",
proplist:(
name:"SEQUENTIAL",
proplist:(
name:"SIMULTANEOUS",
proplist:(
name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
)endlist,
name:"SIMULTANEOUS",
proplist:(
name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
)endlist,
.
.
.
)endlist
name:"SEQUENTIAL",
proplist:(
name:"SIMULTANEOUS",
proplist:(
name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
)endlist,
.
.
.
)endlist
)endlist
)endlist
2.3.5. The Media
So far no explicit description has been given for the media classes
which fit into a PE. It is not known what types of media will be
supported in the various document stations in the future. Those for
which support is in part already available are:
TEXT
VOICE
FACSIMILE
GRAPHICS
Standard formats for data in each of these media must be defined.
Postel [Page 21]
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A Structured Format for Transmission of Multi-Media Documents
Specification
2.3.6. TEXT
The text data may be structured according to a variety of protocols
(yet to be defined). The top level of the data structure is a
property list which identifies the protocol, and the version of that
protocol.
name:"TEXT", proplist:(
name:"PROTOCOL", <protocol>,
name:"VERSION", <version>,
name:"DATA", <data>
)endlist
The first protocol is called PARAGRAPH, and the data is a list of
paragraphs, where each paragraph is a text element.
name:"DATA", list:(
text: <paragraph>
text: <paragraph>
.
.
.
)endlist
2.3.7. VOICE
Since a good deal of research has been done towards implementing the
transmission of voice data on the ARPANET, the Network Voice
Protocol (NVP) provides the basis for the standard for voice data
[24].
Voice data a property list which specifies the vocoder being used,
the transmission protocol and the parcel data. The parcel data form
is specific to the protocol used and is grouped in lists.
name:"VOICE", proplist:(
name:"VOCODER", <vocoder>,
name:"PROTOCOL", <protocol>,
name:"VERSION", <version>,
name:"DATA", <data>
)endlist
The NVP protocol has a number of parameters, the version number
specifies a certain set of the parameters used by the vocoder
hardware and software to set up timing and define the type of coding
used. It is not expected that within a document the version number
will change.
[Page 22] Postel
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A Structured Format for Transmission of Multi-Media Documents
Specification
NVP itself supports negotiation of these parameters to insure both
ends of a network speech connection 'understand' one another. Since
no such interactive negotiation is possible in a document system,
negotiation capabilities have been excluded. As differing hardware
becomes available new versions may be defined.
For the NVP protocol the data list will take the following form:
name:"DATA", list:(
bitstr: <parcel>
bitstr: <parcel>
.
.
.
)endlist
The items in the list are parcels. The individual parcels are bit
string data elements whose contents and length are predefined by the
version number. The number of parcels in a parcel group is
available from the item count in the enclosing list header.
2.3.8. FACSIMILE
There are a number of facsimile devices in use. While standards are
being established by CCITT [25], of the devices available today many
are incompatible due to proprietary compression algorithms. The
description of fax data will allow for the possibility of several
protocols.
name:"FACSIMILE", proplist:(
name:"DEVICE", <device>,
name:"PROTOCOL", <protocol>,
name:"DATA", <data>
)endlist
There are few facsimile devices interfaced to computers though, and
the existing experiments in the ARPANET all use the RAPICOM 450. A
first facsimile standard format will be based on the data structure
used for this machine [26]. That is, for device RAPICOM450 and
protocol BLOCK, the data will be:
name:"DATA", list:(
bitstr:<r450-block>,
bitstr:<r450-block>,
.
.
.
)endlist
Postel [Page 23]
August 1980
A Structured Format for Transmission of Multi-Media Documents
Specification
Where an r450-block is a 585 bit unit.
2.3.9. GRAPHICS
The situation for graphics bears much similarity to facsimile.
Devices on the market today have a variety of user interfaces and
options. A similar structure is defined.
name:"GRAPHICS", proplist:(
name:"DEVICE", <device>,
name:"PROTOCOL", <protocol>,
name:"DATA", <data>
)endlist
There are several candidate protocols for use in describing graphics
data in documents. One is the Network Graphics Protocol [27],
another is the Graphics Language [28,29], and a third is the
SIGGRAPH Core System [30].
[Page 24] Postel
August 1980
A Structured Format for Transmission of Multi-Media Documents
3. EXAMPLES & SCENARIOS
Example 1: Text Example
Suppose we want to send the following message:
Date: 1979-03-29-11:46-08:00
From: Jon Postel <Postel@ISIF>
Subject: Meeting Thursday
To: Danny Cohen <Cohen@ISIB>
CC: Linda
Danny:
Please mark your calendar for our meeting Thursday at 3 pm.
--jon.
It will be encoded in the structured format. The following will
present successive steps in the top down generation of this message.
The identification and command portions of the messages will not be
expanded here (see [1]).
1. message
2. (identification, command, document)
3. (ID:<<identification>>,
CMD:<<command>>,
DOC:( date, from, subject, to, cc, body))
4. (ID:<<identification>>,
CMD:<<command>>,
DOC:(DATE:date,
FROM:from
SUBJECT:subject,
TO:to,
CC:cc,
BODY:body))
5. (ID:<<identification>>,
CMD:<<command>>,
DOC:(DATE: 1979-03-29-11:46-08:00,
FROM: (NET:ARPANET,HOST:ISIF,USER:Postel,PERSON:Jon Postel),
SUBJECT: Meeting Thursday,
TO: (NET:ARPANET,HOST:ISIB,USER:Cohen,PERSON:Danny Cohen),
CC: (NET:ARPANET,HOST:ISIF,USER:Linda),
BODY:
Danny:
Postel [Page 25]
August 1980
A Structured Format for Transmission of Multi-Media Documents
Examples & Scenarios
Please mark your calendar for our meeting
Thursday at 3 pm.
--jon.))
6. PROPLIST:
(ID:<<identification>>,
CMD:<<command>>,
DOC:
PROPLIST:(
DATE: 1979-03-29-11:46-08:00,
FROM:
LIST:(
PROPLIST:(
NET:ARPANET,
HOST:ISIF,
USER:Postel,
PERSON:Jon Postel,
)ENDLIST,
)ENDLIST,
SUBJECT: Meeting Thursday,
TO:
LIST:(
PROPLIST:(
NET:ARPANET,
HOST:ISIB,
USER:Cohen,
PERSON:Danny Cohen,
)ENDLIST,
)ENDLIST,
CC:
LIST:(
PROPLIST:(
NET:ARPANET,
HOST:ISIF,
USER:Linda,
)ENDLIST,
)ENDLIST,
BODY:
Danny:
Please mark your calendar for our meeting
Thursday at 3 pm.
--jon.
)ENDLIST
)ENDLIST
[Page 26] Postel
August 1980
A Structured Format for Transmission of Multi-Media Documents
Examples & Scenarios
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