RFC:767
A STRUCTURED FORMAT FOR TRANSMISSION OF MULTI-MEDIA DOCUMENTS
Jonathan B. Postel
August 1980
Information Sciences Institute
University of Southern California
4676 Admiralty Way
Marina del Rey, California 90291
(213) 822-1511
< INC-PROJECT, MMMSFS.NLS.21, >, 5-Sep-80 20:19 JBP ;;;;
Postel
August 1980
A Structured Format for Transmission of Multi-Media Documents
TABLE OF CONTENTS
PREFACE ........................................................ iii
1. INTRODUCTION ..................................................... 1
1.1. Motivation ................................................... 1
1.2. Scope ........................................................ 1
1.3. Terminology .................................................. 1
1.4. Document Description ......................................... 2
1.5. Other Work ................................................... 2
2. SPECIFICATION .................................................... 3
2.1. Document ..................................................... 3
2.2. Message Objects ............................................. 5
2.3. Body Structures ............................................. 13
2.3.1. Simple Elements ........................................... 13
2.3.2. Structured Text ........................................... 13
2.3.3. NLS File Example .......................................... 13
2.3.4. Multimedia Structures ..................................... 15
2.3.5. The Media ................................................. 21
2.3.6. TEXT ...................................................... 22
2.3.7. VOICE ..................................................... 22
2.3.8. FACSIMILE ................................................. 23
2.3.9. GRAPHICS .................................................. 24
3. EXAMPLES & SCENARIOS ............................................ 25
Example 1: Text Example .......................................... 25
Example 2: Multimedia Example .................................... 28
REFERENCES .......................................................... 31
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A Structured Format for Transmission of Multi-Media Documents
PREFACE
This is the first edition of this format specification and should be
treated as a request for comments, advice, and suggestions. A great
deal of prior work has been done on computer aided message systems and
some of this is listed in the reference section. This specification was
shaped by many discussions with members of the ARPA research community,
and others interested in the development of computer aided message
systems. This document was prepared as part of the ARPA sponsored
Internetwork Concepts Research Project at ISI.
Jon Postel
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A Structured Format for Transmission of Multi-Media Documents
RFC: 767 J. Postel
USC-ISI
August 1980
A STRUCTURED FORMAT FOR TRANSMISSION OF MULTI-MEDIA DOCUMENTS
1. INTRODUCTION
This document describes a format for transmitting structured data
representations of multimedia documents. This format is intended to be
used with the Internet Message Protocol in an internetwork message
delivery system. That system is designed to transmit messages between
processes in host computers called Message Processing Modules (MPMs).
MPMs are located in several networks and together constitute an
internetwork message delivery system. The Internet Message Protocol
defines a message as being composed of an Identification, a Command, and
a Document. This report is intended to define the format of such
Documents. The reader is assumed to be familiar with the Internet
Message Protocol [1].
1.1. Motivation
Computer applications are being implemented which interact with users
in a variety of media (text, graphics, facsimile, speech). As
computer devices become available to process multimedia information it
becomes desirable to use computers to exchange multimedia information
between programs and users via various mechanisms including computer
mail.
1.2. Scope
This format is intended to be used for the transmission of multimedia
documents in the internetwork message delivery system, but it is
thought that it has a wider applicability.
1.3. Terminology
The messages are routed by a process called the Message Processing
Module or MPM. Messages are created and consumed by User Interface
Programs (UIPs) in conjunction with users.
The basic unit transferred between MPMs is called a message. A
message is made up of a transaction identifier (which uniquely
identifies the message), a command (which contains the necessary
information for delivery), and document. The document is a data
structure.
For a personal letter the document body corresponds to the contents of
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Introduction
the letter; the document header corresponds to the date line,
greeting, and signature.
For an inter-office memo the document body corresponds to the text;
the document header corresponds to the header of the memo.
The commands correspond to the information used by the Post Office or
the mail room to route the letter or memo. Some of the information in
the command is supplied by the UIP.
1.4. Document Description
The document is composed of fields. Each field will carry an
identifying name. Typical fields are DATE, TO, SUBJECT, and BODY.
Most of the fields will be very simple, some will be complex. The
body field may be quite complex. For example, the DATE is a very
constrained character string specifying the date and time in ISO
format. A more complex example is the TO field which is a list of
mailboxes, where a mailbox is itself a property list of address
information items. The BODY may be simply a character string, or a
very structured collection of data representing information in
different media.
The BODY may be structured to indicate a controlled presentation of
multimedia information. There is provision for the inclusion of text,
graphics, facsimile, and voice information in the body of documents.
The presentation of information units may sequential, independent, or
simultaneous.
1.5. Other Work
This protocol the benefited from the earlier work on message protocols
in the ARPA Network [2,3,4,5,6], and the ideas of others about the
design of computer message systems [7,8,9,10,11,12,13,14,15,16,17,18].
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2. SPECIFICATION
The structured format of a document is built on the basic data elements
used in the Internet Message Protocol [1].
2.1. Document
The document is a property list of <name,value> pairs called fields.
A few fields are specifically required and many are optional. Some of
the field values are simple and a few are quite complicated. In
particular the body value may be highly structured.
Older message systems have considered the document to be divided into
a header and a body, and have used keywords to indicate specific
header fields (e.g., date, to, subject). Roughly speaking, this
functionality is provided in this new structured format by considering
the name part of the <name,value> pair to be a keyword. In addition,
this new structured format eliminates the separate treatment of the
body.
It is impossible to foresee the many forms documents will take so the
standard for a document header must be flexible. The approach here is
to define a set of basic fields and allow addition of whatever fields
are necessary. Features added in this fashion may not be understood
by others.
The minimum document is a property list of the following fields:
Name Value
---- -----
DATE date string (name)
SENDER a mailbox
SUBJECT subject string (text)
BODY a data structure
A typical document is a property list containing the following fields:
Name Value
---- -----
DATE date string (name)
SENDER a mailbox
FROM list of mailboxes
TO list of mailboxes
CC list of mailboxes
SUBJECT subject string (text)
BODY a data structure
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An elaborate document might contain the following fields:
Name Value
---- -----
DATE date string (name)
SENDER a mailbox
FROM list of mailboxes
TO list of mailboxes
CC list of mailboxes
BCC list of mailboxes
REPLY-TO list of mailboxes
SUBJECT subject string (text)
COMMENTS comment string (text)
MESSAGE-ID message identifier of this message (text)
IN-REPLY-TO message identifier of previous message (text)
REFERENCES message identifiers of other messages (text)
KEYWORDS key terms used in this message (text)
BODY a data structure
One of the key objects is the mailbox. It appears in the sender,
from, to, cc, bcc, and reply-to fields. The mailbox is a property
list of objects that combine to specify a destination recipient for a
message. Most of the <name,value> pairs that make up a mailbox are
identical to those used in the deliver command in the Internet Message
Protocol [1]. A few additional <name,value> pairs are defined for use
in a mailbox in the document context. In particular, there is a field
for the real name of a person in contrast to the "user name" which
identifies a computer account.
In addition there is a field to specify a distribution group name.
Such group names are used to indicate that a document is being sent to
a group of recipients. This essentially presents an alternate form
for a mailbox which consists of the single <name,value> pair for the
group name. There is no required relationship between a group name
mailbox and other mailboxes in the same list.
For example, all of the following situations are allowed:
. a mailbox list consisting of a single mailbox specifying a
particular user,
. a mailbox list consisting of a single mailbox with a group name,
. a mailbox list consisting of a mailbox with a group name and a
mailbox specifying a particular user, with either the user in or
not in the group,
. a mailbox list consisting of a mailbox with a group name and a
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Specification
several mailboxes specifying a particular users, with some users
in the group and some not,
. a mailbox list consisting of several mailboxes specifying group
names and a several mailboxes specifying a particular users, with
some users in the groups and some not.
2.2. Message Objects
In the documents of messages, we use a set of objects such as mailbox
or date. These objects are encoded in basic data elements. Some
objects are simple things like integers or character strings, other
objects are more complex things like lists or property lists. The
following is a list of the objects used in messages. The object
descriptions are in alphabetical order.
Account
The account information. Represented by a name element.
Address
Address is intended to contain the minimum information necessary to
identify a user, and no more (compare with mailbox).
An address is a property list which contains the following
<name,value> pairs:
name description
---- -----------
NET network name
HOST host name
USER user name
or:
name description
---- -----------
MPM mpm-identifier
USER user name
Answer
A yes (true) or no (false) answer to a question. Represented by a
boolean element.
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BCC
A list of mailboxes. The addresses of those who receive "blind
carbon copies" of the message.
Body
A data structure. This may be as simple as a character string
(represented by a name or text element), or complex structure of
lists. It may be encrypted in part or in whole. Section 3.3
describes some possible structured bodies.
C
A character. Represented by a name element.
CC
A list of mailboxes. When copies of a message are sent to others in
addition to the addresses in the To object, those to whom the copies
are sent will have their addresses recorded here.
City
A city. Represented by a name element.
Comments
A comment string. Represented by a text element.
Count
A count of items of some sort. Represented by a integer element.
Country
A country. Represented by a name element.
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Date
The date and time are represented according to the International
Standards Organization (ISO) recommendations [19,20,21]. Taken
together the ISO recommendations 2014, 3307, and 4031 result in the
following representation of the date and time:
yyyy-mm-dd-hh:mm:ss,fff+hh:mm
Where yyyy is the four-digit year, mm is the two-digit month, dd is
the two-digit day, hh is the two-digit hour in 24 hour time, mm is
the two-digit minute, ss is the two-digit second, and fff is the
decimal fraction of the second. To this basic date and time is
appended the offset from Greenwich as plus or minus hh hours and mm
minutes.
The time is local time and the offset is the difference between
local time and Coordinated Universal Time (UTC). To convert from
local time to UTC algebraically subtract the offset from the local
time.
For example, when the time in
Los Angeles is 14:25:00-08:00
the UTC is 22:25:00
or when the time in
Paris is 11:43:00+01:00
the UTC is 10:43:00
Device
A device name. Represented by a name element.
Document
A property list of fields.
Distribution Group
An distribution group is a property list which contains the
following <name,value> pair:
name description
---- -----------
GROUP document distribution group name
This construct is used so that a distribution group will be a
special case of a mailbox.
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Facsimile Structure
A facsimile data structure. Represented by a property list.
File
A file name. Represented by a name element.
Format
A format indicator. Represented by a name element.
From
A list of mailboxes. The From is the name of the author of a
document.
Graphics Structure
A graphics data structure. Represented by a property list.
Group
A document distribution group name. Represented by a name element.
Host
A host name. Represented by a name element.
Ident
The identifier of a person, usually their initials. Represented by
a name element.
In-Reply-To
The message identifier of previous message. Represented by a text
element.
Internet Address
This identifies a host in the ARPA internetwork environment. The
internet address is a 32 bit number, the higher order 8 bits
identify the network, and the lower order 24 bits identify the host
on that network [22]. For use in this format the internet address
is divided into eight bit fields and the value of each field is
represented in decimal digits. For example, the ARPANET address of
ISIE is 167837748 and is represented as 10,1,0,52. Further, this
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representation may be extended to include an address within a host,
such as the TCP port of an MPM, for example, 10,1,0,52,0,45.
Keywords
The key terms used in this message. Represented by a text element.
Mailbox
This is the destination address of a user of the internetwork mail
system. Mailbox contains information such as network, host,
location, and local user identifier of the recipient of the message.
The mailbox may contain information in addition to the minimum
required for delivery.
As an example, when one sends a message to someone for the first
time, he may include many items to aid in identifying the correct
recipient. However, once he gets a reply to this message, the reply
will contain an Address (as opposed to Mailbox) which may be used
from then on.
A mailbox is a property list. A mailbox might contain the
following <name,value> pairs:
name description
---- -----------
MPM mpm-identifier
NET network name
HOST host name
PORT address of MPM within the host
USER user name (computer account name)
PERSON the real name of a person
GROUP document distribution group
ORG organization name
CITY city
STATE state
COUNTRY country
ZIP zip code
PHONE phone number
The minimum mail box is an Address or a Distribution Group.
Message-ID
The message identifier of this message. This is not related to the
MPM message identification, but is a UIP long term document
identifier. Represented by a text element.
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MPM-Identifier
The internetwork address of an MPM. This may be the ARPA Internet
Address or an X.121 Public Data Network Address [23]. The
mpm-identifier is a property list which has one <name,value> pair.
This unusual structure is used so that it will be easy to determine
the type of address used.
Net
A network name. Represented by a name element.
NLS Block
The information in an NLS node. Represented by a property list.
NLS Node
An NLS block and substructure. Represented by a property list.
NLS Substructure
A list of NLS nodes. Represented by a list.
Org
An organization name. Represented by a name element.
Paragraph
A paragraph of text. Represented by a text element.
Parcel
The basic unit of voice data. Represented by a bitstr element.
Person
The real name of a person. Represented by a name element.
Password
A password. Represented by a name element.
Phone
A phone number. Represented by a name element.
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Pointer
A pointer to information stored outside this data structure. A
property list containing the information necessary to locate the
external data, the information necessary to gain access to the
external data, and the information necessary to apply the correct
interpretation to the external data. For example, this might
include:
name description
---- -----------
NET network name
HOST host name
FILE file name
USER user name (computer account name)
PASSWORD password
ACCOUNT account
FORMAT format
Port
The address of MPM within the host. Represented by a name element.
Presentation Descriptor
A property list of <name,value> pairs, where the name is an order
indicator, and the value is a presentation element. The order
indicators are SEQUENTIAL, SIMULTANEOUS, and INDEPENDENT.
Presentation Element
A property list of media structures.
Protocol
The name of the coding scheme used for a medium. Represented by a
name element.
References
The message identifiers of other messages. Represented by a list of
text elements.
Reply-To
A list of mailboxes. Sometimes it will be desired to direct the
replies of a message to some address other than the from or the
sender. In such a case the reply-to object can be used.
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R 450 Block
The unit of Rapicom 450 data (585 bits). Represented by a bitstr
element.
Sender
A mailbox. The sender will contain the address of the individual
who sent the message. In some cases this is NOT the same as the
author of the message. Under such a condition, the author should be
specified in the from object.
SID
An NLS statement indetifier. Represented by a integer element.
State
A state name. Represented by a name element.
Subject
The subject of the message. Represented by a text element.
Text Structure
A text data structure. Represented by a property list.
To
A list of mailboxes. To identifies the addressees of the message.
User
A user name (computer account name). Represented by a name element.
Version
A version number. Represented by a index element.
Vocoder
A vocoder name. Represented by a name element.
Voice Structure
A voice data structure. Represented by a property list.
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X121 Address
This identifies a host in the Public Data Network environment. When
used as a part of identifier, it identifies the originating host of
a message. The X121 address is a sequence of up to 14 digits [23].
For use in this format the X121 address is represented in decimal
digits.
ZIP
A zip code. Represented by a name element.
2.3. Body Structures
2.3.1. Simple Elements
The body could simply be a single data element. For example a
single text element can represent a lengthy character string.
<body> := TEXT
or
text:"this is the actual text of the body"
2.3.2. Structured Text
The body could be thought of as paragraphs, where each paragraph is
represented by a text element. The paragraphs are then the elements
of a list.
<body> := LIST (<paragraph>, <paragraph>, ...)
<paragraph> := TEXT
or
list:(text:"paragraph one", text:"paragraph two", ...)
2.3.3. NLS File Example
It is possible to represent the data from NLS files in this format.
NLS is a large multipurpose system which operates on structured data
files. The files are tree structured, and there is data associated
with each node of the tree. There are several fields associated
with each node as well.
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An NLS file is:
proplist( file
name:"FILENAME", name:<file> name of file
name:"CREATION-DATE", name:<date> creation date and time
name:"VERSION", index:<version> file version number
name:"SID-COUNT", integer<count> current SID count
name:"LAST-WRITER", name:<ident> last writer of file
name:"OWNER", name:<ident> owner of file
name:"LAST-WRITE-TIME", name:<date> last write date and time
name:"LEFT-NAME-DELIM-DEFAULT", name:<c> default name
name:"RIGHT-NAME-DELIM-DEFAULT", name:<c> delimiters
name:"SUBSTRUCTURE", <nls-substructure> substructure
)endlist
An NLS substructure is:
list:( substructure
<nls-node> node is defined below
.
.
.
)endlist
An NLS node is:
proplist:( node
name:"BLOCK", <nls-block> block defined below
name:"SUBSTRUCTURE", <nls-substructure> substructure
)endlist
An NLS block is:
proplist:( block
name:"LEFT-NAME-DELIM", name:<c> left name delimiter
name:"RIGHT-NAME-DELIM", name:<c> right name delimiter
name:"SID", integer:<sid> SID number
name:"CREATOR", name:<ident> statement creator
name:"CREATION-TIME", name:<date> creation date and time
name:"DATA", <data> data defined below
)endlist
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NLS data is:
proplist:( data
name:"<a data name>", <type depends on data name>
. .
. .
. .
)endlist
For text, data is:
proplist:( data
name:"TEXT", text:"text of statement" text
)endlist
2.3.4. Multimedia Structures
One can conceive of graphical information being displayed along with
a running commentary, much as seminars use slides. A slide and its
description are tied together. The coordination of such a
presentation is central to its understanding. This synchronization
should be captured within the document structure.
There are three fundamentally different types of time ordered
control which are needed within the document structure. These are:
Simultaneous
Sequential
Independent
Simultaneous data is intended for synchronous presentation. The
implication is that this data is presented in parallel.
Sequential data items will be presented one at a time, in the order
listed. The ordering is strictly left to right.
Independent data can be presented in any time order. It is not
ordered in any manner.
The data is broken into small information units called presentation
elements or PEs. The PEs can be combined in structures to control
the presentation order. A PE is a property list of elements
representing information of various media. For example:
<pe> := proplist(
name:"VOICE", <voice-structure>,
name:"GRAPHICS", <graphics-structure>
)endlist
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PEs are combined into larger controled presentations by
presentation-descriptors or PDs. A PD is a property list which
specifies the type of time ordering of the PEs in its list.
<pd> := <<seq>> | <<sim>> | <<ind>>
<<seq>> := name:"SEQUENTIAL", <pe>
<<sim>> := name:"SIMULTANEOUS", <pe>
<<ind>> := name:"INDEPENDENT", <pe>
A PE is a property list of the media <name,value> pairs, or PDs.
<pe> := <<text>> | <<voice>> | <<facsimile>>
| <<graphics>> | <pd>
<<text>> := name:"TEXT", <text structure>
<<voice>> := name:"VOICE", <voice structure>
<<facsimile>> := name:"FACSIMILE", <facsimile structure>
<<graphics>> := name:"GRAPHICS", <graphics structure>
If more than one <name,value> pair is present within a PE the media
are presented on different output devices in the order specified by
the PE's parent PD. The order of appearance within the proplist is
important only in the event that the parent PD specified sequential
ordering.
The structure of multimedia messages which use this scheme will be
demonstrated by a few simple examples chosen to illustrate a basic
text document and the different ordering options. The last example
will suggest some more exotic uses.
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Plain Text Message
A simple text body could be represented in a single text data
structure. To give the simplest example of a structured body we
show a simple text body represented in the multimedia structure.
<body> := <pd>
<pd> := <<seq>>
<<seq>> := name:"SEQUENTIAL", <pe>
<pe> := name:"TEXT", <text structure>
or
proplist: (name:"SEQUENTIAL",
proplist:(
name:"TEXT", <text structure>
)endlist
)endlist
Simultaneous Ordering
This ordering option is used to indicate when separate streams are
to be presented in parallel. For example, assume GRAPHICS and
VOICE data were to be presented using simultaneously.
<body> := <pd>
<pd> := <<sim>>
<<sim>> := name:"SIMULTANEOUS", <pe>
<pe> := name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
or
proplist:(
name:"SIMULTANEOUS",
proplist:(
name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
)endlist
)endlist
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Sequential Ordering
This option is used to indicate sequential time ordering. The
media in the sub-tree below this PD are not separate streams.
Using again the example above, assume GRAPHICS and VOICE data were
to be presented using sequential ordering.
<body> := <pd>
<pd> := <<seq>>
<<seq>> := name:"SEQUENTIAL", <pe>
<pe> := name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
or
proplist:(
name:"SEQUENTIAL",
proplist:(
name:"VOICE", <voice structure>
name:"GRAPHICS", <graphics structure>
)endlist
)endlist
Independent Ordering
It is apparent that some output devices are very slow in
comparison to others. An example which demonstrates this is
facsimile. The majority of facsimile devices are slow. A
detailed picture transmitted at 9600 baud takes minutes to print.
It is inconvenient for the user to wait on such a device when the
voice or text information which accompanies it is short.
For example, if the document a facsimile image and the text
"Hello Frank, here's a copy of that picture you requested." The
user need not wait for the picture. The facsimile machine might
be spooled, in which case he would pick up the picture later. In
a sense the picture was time independent of the text.
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<body> := <pd>
<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>
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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>
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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.
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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.
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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
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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].
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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:
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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
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Examples & Scenarios
7. proplist:(
name:"ID", <<identification>>,
name:"CMD", <<command>>,
name:"DOC",
proplist:(
name:"DATE", name:"1979-03-29-11:46-08:00",
name:"FROM",
list:(
proplist:(
name:"NET", name:"ARPANET",
name:"HOST", name:"ISIF",
name:"USER", name:"Postel",
name:"PERSON", name:"Jon Postel",
)endlist,
)endlist,
name:"SUBJECT", text:"Meeting Thursday",
name:"TO",
list:(
proplist:(
name:"NET", name:"ARPANET",
name:"HOST", name:"ISIB",
name:"USER", name:"Cohen",
name:"PERSON", name:"Danny Cohen",
)endlist,
)endlist,
name:"CC",
list:(
proplist:(
name:"NET", name:"ARPANET",
name:"HOST", name:"ISIF",
name:"USER", name:"Linda",
)endlist,
)endlist,
name:"BODY",
text:"Danny:
Please mark your calendar for our
meeting Thursday at 3 pm.
--jon."
)endlist
)endlist
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A Structured Format for Transmission of Multi-Media Documents
Examples & Scenarios
Example 2: Multimedia Example
proplist:(
name:"ID", <<identification>>,
name:"CMD", <<command>>,
name:"DOC",
proplist:(
name:"DATE", name:"1980-08-06-11:46-08:00",
name:"FROM",
list:(
proplist:(
name:"NET", name:"ARPANET",
name:"HOST", name:"ISIF",
name:"USER", name:"Postel",
name:"PERSON", name:"Jon Postel",
)endlist,
)endlist,
name:"SUBJECT", text:"Multimedia Test Message",
name:"TO",
list:(
proplist:(
name:"GROUP", name:"Multimedia Experiment List",
)endlist,
)endlist,
name:"CC",
list:(
proplist:(
name:"NET", name:"ARPANET",
name:"HOST", name:"ISIF",
name:"USER", name:"Linda",
)endlist,
)endlist,
name:"BODY",
proplist:(
name:"SEQUENTIAL",
proplist:(
name:"TEXT",
proplist:(
name:"PROTOCOL", name:"PARAGRAPH",
name:"VERSION", index:"1",
name:"DATA",
list:(
text:"This is a test of multimedia mail."
text:"I hope you like it."
)endlist
)endlist
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A Structured Format for Transmission of Multi-Media Documents
Examples & Scenarios
name:"SIMULTANEOUS",
proplist:(
name:"VOICE",
proplist:(
name:"VOCODER", name:<vocoder>,
name:"PROTOCOL", name:"NVP",
name:"VERSION", index:"1",
name:"DATA",
list:(
bitstr:<parcel>
bitstr:<parcel>
)endlist
)endlist
name:"GRAPHICS",
proplist:(
name:"DEVICE", name:<device>,
name:"PROTOCOL", name:<protocol>,
name:"VERSION", index:<version>,
name:"DATA",<data>
)endlist
)endlist
)endlist
name:"SEQUENTIAL",
proplist:(
name:"TEXT,
proplist:(
name:"PROTOCOL", name:"PARAGRAPH",
name:"VERSION", index:"1",
name:"DATA",
list:(
text:"That was supposed to be some voice
and graphics in parallel."
text:"--jon."
)endlist
)endlist
)endlist
)endlist
)endlist
)endlist
Postel [Page 29]
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[Page 30] Postel
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A Structured Format for Transmission of Multi-Media Documents
REFERENCES
[1] Postel, J., "Internet Message Protocol," RFC 759, 113,
USC/Information Sciences Institute, August 1980.
[2] Bhushan, A., K. Pogran, R. Tomlinson, and J. White, "Standardizing
Network Mail Headers," RFC 561, NIC 18516, September 1973.
[3] Myer, T., and D. Henderson, "Message Transmission Protocol,"
RFC 680, NIC 32116, 30 April 1975.
[4] Crocker, D., J. Vittal, K. Pogran, and D. Henderson, "Standard for
the Format of ARPA Network Text Messages," RFC 733, NIC 41952,
21 November 1977.
[5] Barber, D., and J. Laws, "A Basic Mail Scheme for EIN," INWG 192,
February 1979.
[6] Braaten, O., "Introduction to a Mail Protocol," Norwegian
Computing Center, INWG 180, August 1978.
[7] Crocker, D., E. Szurkowski, and D. Farber, "An Internetwork Memo
Distribution Capability - MMDF," Sixth Data Communications
Symposium, ACM/IEEE, November 1979.
[8] Haverty, J., D. Henderson, and D. Oestreicher, "Proposed
Specification of an Inter-site Message Protocol," 8 July 1975.
[9] Thomas, R., "Providing Mail Services for NSW Users," BBN NSW
Working Note 24, Bolt Beranek and Newman, October 1978.
[10] White, J., "A Proposed Mail Protocol," RFC 524, NIC 17140, SRI
International, 13 June 1973.
[11] White, J., "Description of a Multi-Host Journal," NIC 23144, SRI
International, 30 May 1974.
[12] White, J., "Journal Subscription Service," NIC 23143, SRI
International, 28 May 1974.
[13] Levin, R., and M. Schroeder, "Transport of Electronic Messages
Through a Network," Teleinformatics 79, Boutmy & Danthine (eds.)
North Holland Publishing Co., 1979.
[14] Earnest, L., and J. McCarthy, "DIALNET: A Computer Communications
Study," Computer Science Department, Stanford University, August
1978.
Postel [Page 31]
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A Structured Format for Transmission of Multi-Media Documents
References
[15] Crispin M., "DIALNET: A Telephone Network Data Communications
Protocol," DECUS Proceedings, Fall 1979.
[16] Caulkins, D., "The Personal Computer Network (PCNET) Project: A
Status Report," Dr. Dobbs Journal of Computer Calisthenics and
Orthodontia, v.5, n.6, June 1980.
[17] Postel, J., "NSW Transaction Protocol (NSWTP)," USC/Information
Sciences Institute, IEN 38, May 1978.
[18] Haverty, J., "MSDTP -- Message Services Data Transmission
Protocol," RFC 713, NIC 34739, April 1976.
[19] ISO-2014, "Writing of calendar dates in all-numeric form,"
Recommendation 2014, International Organization for
Standardization, 1975.
[20] ISO-3307, "Information Interchange -- Representations of time of
the day," Recommendation 3307, International Organization for
Standardization, 1975.
[21] ISO-4031, "Information Interchange -- Representation of local time
differentials," Recommendation 4031, International Organization
for Standardization, 1978.
[22] Postel, J., "DOD Standard Internet Protocol," USC/Information
Sciences Institute, IEN 128, NTIS number AD A079730, January 1980.
[23] CCITT-X.121, "International Numbering Plan for Public Data
Networks," Recommendation X.121, CCITT, Geneva, 1978.
[24] Cohen, D., "Specifications for the Network Voice Protocol (NVP),"
NIC 42444, RFC 741, NSC 68, RR-75-39, USC/Information Sciences
Institute, January 1976.
[25] CCITT-T.30, "Procedures for Document Facsimile Transmission in the
General Switched Telephone Network," Recommendation T.30, Orange
Book, V. 7, The International Telephone and Telegraph Consulative
Committee, International Telecommunication Union, Geneva, 1977.
[26] Treadwell, S., "FAX File Format," ARPANET Message, 14 November
1979.
[27] Sproull, R., and E. Thomas, "A Network Graphics Protocol,"
NIC 24308, Xerox Palo Alto Research Center, August 1974.
[Page 32] Postel
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A Structured Format for Transmission of Multi-Media Documents
References
[28] Bisbey, R., and D. Hollingworth, "A Distributable,
Display-Device-Independent Vector Graphics System for Command and
Control," RR-80-87, USC/Information Sciences Institute, July 1980.
[29] Bisbey, R., D. Hollingworth, and B. Britt, "Graphics Language,"
TM-80-18, USC/Information Sciences Institute, July 1980.
[30] Graphics Standard Planning Committee, "Core System," Computer
Graphics, V. 13, N. 3, SIGGRAPH, ACM, August 1979.
Postel [Page 33]
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|
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