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Filed as[Indigo]<Interscript>Slides>forum-2dec82.slides, .press
Last editedBy Mitchell on December 1, 1982 12:05 AM
First slide should be a copy of the xerox ad (get Subhana to find and make a reduced transparency of one), or a diagram suggesting interchange among Star, 820, Tioga, MemoryWriter, ...
InterScript
What is it?
Why is it being done?
Who is involved?
How would I know one if I saw it?
What does Interscript look like?
What are the interesting (hard) problems?
What will become of it?
What is it?
A standard,
static
digital representation
for interchanging documents
among editing systems
Why is it being done?
Customers need to be able to interchange documents
Xerox needs it for its N document editing products
Possible solutions:
1.Develop N(N-1) conversion routines
2a.Develop 2(N-1) "indirect" conversion routines
2b.Develop 2(N-1) editor-independent, indirect conversion routines
Who is involved?
PARC OSD
Jim HorningBob Ayers
Butler LampsonGael Curry
Scott McGregorJean-Marie de La Beaujardiere
Jim MitchellPhil Karlton
Jane Stepak
What properties should it have?
The encoding should be space- and time-efficient
It must be extendible
Both form and content have to be represented
Structure has to be represented
It must transcribe faithfully [better phrase needed]
It must work with editors of varying capabilities
What doesn’t it cover?
It is not a file format
It is not a standard for editing
It is not an editing system itself
How does it compare with InterPress?
Commonalities
language-based
basis + extension
contextual independence
Differences
InterScriptInterPress
structural varietysequence of pages
structure mattersstructure not important
scripts are compiledmasters are executed
What does it look like?
The standard is layered
It’s language-based
Scripts
Internalization
Externalization
Layers of the Standard
Layer 0:the syntax of the Interscript language
Layer 1:the semantics of the language
Layer 2:the semantics of properties and attributes expected to have a standard interpretation
Layer 0: Syntax
Layer 1: The semantic model
primary structure represented by nodes
values
marks
content
bindings
indirection
links
Layer 2: Standard Properties
How would it be used?
properties that any solution should have
What are the interesting (hard) problems?
Page contents
What will become of it?
Page contents
PageHeading
The interchange format as a language
Layers of the standard
Content, form, value, and structure
Features of the base language
Transcription and rendition fidelity
The interchange format as a language
A script is a program in the Interscript language
Transcription:
editor representation —> interchange
(document —> script)
Every script is transcribed before being editable
Rendition:
interchange —> editor representation
(script —> document)
Layers of the standard
Layer 0: The syntax of scripts
Layer 1: The semantics of the base language
Layer 2: The semantics of generally shared properties and attributes
Layer 3: The semantics of properties and attributes to be shared by groups of communicating editors
Content, form, value, and structure
Content: "What" is in the document
Form: "How" it is to be viewed
Structure: Intended relations among values
Issues in Transcription
Fidelity: R(T(document)) = document
Process in left-to-right, depth-first order—to transmit without first storing
Standard external environment: units, definitions, abbreviations, . . .
T(R(T(document))) need not necessarily be the same as T(document) — extra hints are okay
Standard versus editor-specific transcription
Issues in Regeneration
S1 ← T1( D1) D2 ← R2(S1) S2 ← T2(D2)
S1 = S2?D1 = R1(S2)?
S1 ← T1( D1) D’2 ← Edit(R2(S1)) S’2 ← T2(D’2)
What relation is there between S1 and S’2?
Determining which nodes have been altered directly or indirectly
Regenerating structure when relevant parts of the environment and contents have not changed since rendering
Can it be done as simply as normal transcription?
Requirements and Exclusions
An interchange standard must:
Preserve document structure
Preserve document form
Provide faithful transcriptions
Simplify limited-fidelity rendition
Enable regeneration of scripts after editing with unaffected portions faithfully transcribed
Interscript is not:
A file format
A standard for editing
A mechanism for combining documents
A substitute for other corporate standards
STANDARD DISCLAIMERS
1.WE ARE DESIGNING A STANDARD FOR INTERCHANGE, NOT EDITING.
2.EVERY SCRIPT IS RENDERED (parsed) BEFORE BEING EDITABLE.
3.STANDARDIZE CONCEPTS, NOT NAMES
4.COMBINING DOCUMENTS IS AN EDITOR, NOT AN INTERCHANGE TASK (corollary of 1).
5.GENSYM IS AN EDITOR FUNCTION (corollary of 1).
6.CHARACTER-SET AND LEXICAL ISSUES CAN BE RESOLVED AT THE END.
7.GET THE TECHNICAL BASIS RIGHT BEFORE WORRYING ABOUT THE POLITICAL ISSUES.