The INTERSCRIPT Standard
Draft 2.0
September 1983
    
    Current Status
    
    
    Overview of the standard's technical content
    
    
    What needs to be done

Current Status
    
    Draft Standard "Version 2.0/September 1983" published
    
    
    There has been almost no experimental implementation
    
    
    There are still technical details to be worked out
    
    
    Other documents are needed 

Contents of the Draft Standard

    1. Introduction
    2. The Language Basis: Syntax and Semantics
    3. Tag Declaration, Node Invariants, and Safety Rules for Editors
    4. Standard Document Constructs
    5. Layout
    6. Other Constructs
    7. Encoding
    Appendix A:  Glossary
    Appendix B:  Example of Script Evaluation
    Appendix P:  Paragraph% ReducesTo
    Appendix Q:  Line% ReducesTo

Current Status
    Rating: 1nonexistent
        . . .
             5first draft
        . . .
             10well polished
    7   1. Introduction
    8   2. The Language Basis: Syntax and Semantics
    6   3. Tag Declaration, Node Invariants, and Safety Rules for Editors
    6   4. Standard Document Constructs
    5   5. Layout
    6   6. Other Constructs
    7   7. Encoding
    6   Appendix A:  Glossary
    8   Appendix B:  Example of Script Evaluation
    6   Appendix P:  Paragraph% ReducesTo
    6   Appendix Q:  Line% ReducesTo
    1   Index

Layer 0: Syntax  (Publication Encoding)
    script  ::=  header node trailer
    header  ::=  "INTERSCRIPT/INTERCHANGE/1.0 "
    trailer  ::=  "ENDSCRIPT"
    item  ::=  tag | indirection | binding | sBinding | term |
               openedNode | scope
    items  ::=  empty | items item
    tag  ::=  primary "$"
    openedNode  ::=  (term | name "%") "|"
    scope  ::=  "[" items "]"
    binding  ::=  name "_" term
    sBinding  ::=  name "%_" ( term | indirection |  "'" term "'" )
    term  ::=  primary | term op primary
    op  ::=  "+" | "" | "*" | "/" | "!" | "LT" | "EQ"
    primary  ::=  literal | invocation | node | "(" term ")"
    literal  ::=  name | number | string
    name  ::=  id | name "." id
    invocation  ::=  primary  "^"
    indirection  ::=  name "%"
    node  ::=  "{" items "}"
Examples of Syntax
    INTERSCRIPT/INTERCHANGE/1.0
        { -- body of the script -- }
    ENDSCRIPT
    INTERSCRIPT/INTERCHANGE/1.0
    {Text$ "Now is the ... party." "A second string"
      font_{Font$ name_Helvetica}}
    ENDSCRIPT
    INTERSCRIPT/INTERCHANGE/1.0
    {Paragraph$ lineJustification_1 leftMargin_1.0*inch
        {Text$ "Now is the ... party." "A second string"
         font_{Font$ name_Helvetica}}
    } ENDSCRIPT
    INTERSCRIPT/INTERCHANGE/1.0
    {BarChart$
      xEdge_{edge | range_{1970 1980} delta_1 lbl_"Year"}}
      yEdge_{edge | range_{0 11.5} delta_0.5
                        lbl_"Corn(tons)"}
    {1970 7.7} {1980 11.2} {1973 7.8}
    } ENDSCRIPT

Layer 1: Semantics
    value space: atoms, numbers, strings, nodes, quoted expressions
    bindings and content
    structure: bindings, evaluation
    scope for names
    external environment
    The Interscript semantic function maps a script into a tree
        two scripts are equivalent if their semantic representations are equal

Formal Semantics

Lefthand Side  Alternative        S[
script  ::=  node           S[X, node]
items  ::=  empty           empty
             | items item         {t: VS=S[                        ConcatVs[t, S[ConcatVs[
tag  ::=    primary           MkTag[
scope  ::=  items           MkScope[S[
openedNode  ::=  term           Items[S[          | name           MkV[m: onodeStruc,
                           cVs: Items[evalName[
binding  ::=  name term          MkBinding[
sBinding  ::=  name sRhs      MkBinding[
quoted  ::=  term          MkV[m: quotedTerm, cTerm: term]
term  ::=  term op primary    apply[op, S[
literal  ::=  name          MkV[m: atom, xName: S[NIL, name]]
    | number          MkV[m: num, cNum: number]
    | string          MkV[m: string, cStr: string]
name  ::=  id          MkAtom[id]
    | name id          CONS[MkAtom[id], S[NIL, name]]
invocation  ::=  primary       evalName[
indirection    ::=  name         MkV[m: evalStruc, cV: evalName[                            name]], xName: S[NIL, name]]
node  ::=  items         {t: Vs=S[             MkNode[ConcatVs[

Safe Editing
    A tag on a node is like a type in Mesa
    A tag definition specifies
        relevant attributes
        other required tags
        allowed parent tags
        type of the contents
        a node invariant
        what more basic tag it can be reduced to (if any)
    Tag definitions enable an editor to edit safely nodes with tags that it doesn't directly implement

Next Steps
    Feedback on the draft standard
    Trial implementations
    Final version of the standard
    Implementor's guide