Re: [eclipse-incubator-e4-dev] Fw: Declarative UI roundup?

[Michael Scharf <Michael.Scharf@xxxxxxxxxxxxx>]

I played with JSON [1] some time ago and I think it is lacking the
notion of id/references and notion of type/class [2]. The only
structure elements you have are arrays and maps (which is ironically
called "object").

So, JSON might be OK when you have a schema and you know the
meaning of the attributes (id or reference), but you have to
introduce some artificial attributes to extract the "class" from
a map:

here is a simple "schema" using emfatic[2] syntax:

  class Control {
    id attr String id; // an id to be referenced
    attr String[*] name;
    ref Composite container; // ref means a reference to an id attribute
  }

  class Text extends Control {
    attr String text;
  }

  class Label extends Control {
    attr String text;
  }

  class Composite extends Widget {
    val Widget[*] widgets; // val means physically nested
  }

"native" JSON serialization cannot distinguish between a text

 {
   "id" : "Control1", // is this an ID or just a string
   "widgets" : [
      { // is this a Text or a Label???
         "id" : "Control2",
         "text" : "Control1", // is this a string or a reference???
         "container" : "Control1"
      },
      {
         "id" : "Control3",
         "text" : "foo bar",
         "container" : "Control1"
      }
   ]
 }

Without additional information (that goes beyond the JSON specs)
it is not possible to figure out if Control2 is a Text or a Label,
because JSON lacks the concept of typed object (or records).

In addition, without a "schema" it is not possible to figure out that
 - "id" : "Control1" defines an ID
 - "container" : "Control1" is a reference
 - "text" : "Control1" is NOT a reference

==> JSON is not self describing (that means: you can not infer
a kind of schema form a data file). And it is not "object
friendly" because you have to add application specific attributes
to specify "object types".

<flame>This *really* annoys me, because more than 20 years ago me
and others have "invented" and used simple self describing data
serialization formats that allow you to extract some (basic) schema
from a datafile. The whole XML (mess) (invented by linguists!) puts an
entire industry into a state where people spend a lot of time
into simple serialization, because it is made so incredibly complicated...

I think JSON is another "bad standard". With some minor enhancements
it could become a useful format for object serialization, but as it is
it is almost as bad as XML....
</flame>

Michael

[1] http://www.json.org/
    http://www.ietf.org/rfc/rfc4627.txt?number=4627
[2] http://michaelscharf.blogspot.com/2007/06/i-dont-like-xml-but-what-are.html
[3] http://wiki.eclipse.org/Emfatic


Ed Merks wrote:
> David,
>
> Marcelo has a prototype for a JSON serializer.  One deficiency in JSON, 
> which isn't apparent for its primary use case, is that you don't know 
> the type of what you are reading.   Starting at the root, you haven't 
> clue and even when processing children, you never know if the actual 
> data's type is of a class derived from the expected type of data.  This 
> makes it hard to create the right type of object in a strongly typed 
> setting...
>
> Cheers,
> Ed
>
>
> David Orme wrote:
> > This is interesting.  XML is good in that it has tooling, but other 
> > formats are arguably even more wrist and eye-friendly.  Given our web 
> > aspirations, JSON seems particularly interesting...
> >
> > Ed- is there a JSON marshaller for EMF objects yet?
> >
> > -Dave Orme
> >
> >     On Nov 6, 2008 6:47 PM, "向雅" <fyaoxy@xxxxxxxxx
> >     <mailto:fyaoxy@xxxxxxxxx>> wrote:
> >
> >     2 points: an UI declaration, and a thought.
> >     1.an <http://1.an> UI declaration:
> >     above sample can be like this:
> >
> >     @layout: fill;
> >     label: "hello, world"; text{style: BORDER; layoutData: "grow"}
> >
> >     Huge simple?  if yes, again:
> >
> >     @layout: "fill";
> >     @StyleSheet{
> >            text{ style: SINGLE, BORDER;}
> >     };
> >     @forms: true;
> >
> >     section{
> >            @id: loginSection;
> >            sectionStyle: ExpandableComposite.TITLE_BAR;
> >            CompositeSeparator:NONE;
> >            text: 登录系统;
> >            layoutData: "center";
> >            composite{
> >                    @id: sectionClient;
> >                    layout: "wrap 3", "[][250:pref:400,fill][]", "[]5[]";
> >                    label: 您的数字证书：;
> >                    text { @id: certFile; text: ""; }
> >                    button { @id: browse; text: 选择文件(&B)...; style:
> >     PUSH; }
> >
> >                    label: 您的密码：;
> >                    text { @id: password; text: ""; style: PASSWORD; }
> >                    button { @id: login; text: "登录系统(&L)   ";
> >     style: PUSH; }
> >            }
> >            client: @sectionClient;
> >     }
> >
> >     2, a thought: at this time, in the world, the most question is not can
> >     you do. instead, just be: How and what make better.Yes? like David
> >     style, I do answer, sure.:)
> >
> >     Best! qinxian
> >
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> >
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