Hi Doug:

I agree with you assessment of repetition classes.

We had a somewhat related discussion in

http://www.ccs.neu.edu/research/demeter/demeter-method/uml-syntax-discussion

Also see below.

>From dougo@ccs.neu.edu Sat Oct 18 18:53:58 1997
>From: Doug Orleans <dougo@ccs.neu.edu>
>To: dem@ccs.neu.edu
>Subject: repetition classes, RIP?
>
>Speaking of repetition classes and multiplicity edges...
>
>I've been thinking about this for a while now, and I've pretty much
>convinced myself that we should just get rid of repetition classes as
>they are now.  Instead, we should simply allow construction classes to
>have repetition edges, or in UML terms, roles with "0..*" or "1..*"
>multiplicity.  I suggest using a syntax akin to JavaCC's:
>
>    Basket = <contents> ( Fruit )*.	// 0..*
>    Company = <emps> ( Employee )+.	// 1..*
>

Earlier we thought of a syntax like:

<l>
<l:1>           // same as <l>
<l:0..*>
<l:1..3>
<l:1..*>

>
>These edges can be freely combined with ordinary construction and
>optional edges.  We could even generate the edge name automatically by
>pluralizing & lowercasing the class name.
>
>Why?  I just find that having a separate Foo_List class for every time
>I want to have a collection of Foo to be really cumbersome, both
>conceptually and in the class dictionary.  Also, I find the current

Especially users in the information systems community find this
cumbersome.

>syntax for repetition classes to be awkward-- why do I have to mention

Well, that is because of the EBNF heritage. In EBNF you write:
List = S { S }.

>the name of the class twice if it's a 1..* repetition?  The one minor
>problem I see with this new notation is that there's no obvious way to
>specify "between" syntax, e.g. in the current notation,
>
>    Commalist ~ X { "," X }.
>
>This means that there is a comma between each pair of X's in the
>sequence.  However, this is awkward in the current system too, because
>if you want a list that has "between" syntax, it is not allowed to be
>empty, leading to this situation everywhere:
>
>    Foo = [ Commalist ].
>
>I end up doing things like this all over demjava, and it's an annoying
>detail that always gets in the way.
>
>--Doug
>

To solve the between syntax problem, we could use something like:

Company = <emps> ( Employee before: "{" between: ","  after: "}" )+ .    // 1..*

We could also specify the desired (GenVoca) implementation:

Company = <emps> ( Employee before: "{" between: ","  after: "}"  implementation AVL tree )+ .    

-- Karl