1. File System
Regions
Files
Documents

2. List Regions
System
Regioninfo
Add Region
Rid Rh
Rid Rh
Make
Regionid
list files
Region
Fileinfo
Add File
Fid Fh
Fid Fh
Make
Fileid
list documents
File
Docinfo
Add Doc
Did Dh
Did Dh
Make
Docid
Text

3. Structure of the file system specification
BOOLEAN
LIST
PAIR
QUAD
BIMAP
FILESYS

4. LIST LIST (Elem with { - == -: Elem, Elem  Bool; undef : Elem}
sort List
uses BOOLEAN
constants
0 :  List // generates an empty list
undef :  List
first : List  Elem // head
rest : List  List // tail
isundef : List  Bool
-.- : Elem, List  List // add to front
memberOf - : Elem, List  Bool
== - : List, List  Bool
atEnd : List  Bool // isEmpty

5. first(0) = undef
rest(0) = undef
first(undef) = undef
rest(undef) = undef
first(a.b) = a
rest(a.b) = b
atEnd(0) = true
atEnd(undef) = false
atEnd(a.b) = false

6. a.b == c.d = (a==c) and (b==d)
0 == 0 = true
a.b == 0 = false
(a == b) = (b == a)
e memberOf undef = false
e memberOf 0 = false
e memberOf a.b = (e == a) or (e memberOf b)

7. PAIR ( A with { - == -: A, A  Bool; undef : A},
B with { - == -: B, B  Bool; undef : B})
sort Pair
constants undef : Pair
uses BOOLEAN
first : Pair  A
second : Pair  B
pair : A, B  Pair
- == - : Pair, Pair  Bool