Re: XML and Objects

David Brownell (db@Eng.Sun.COM)
Thu, 01 Oct 1998 07:56:35 -0700


Jonathan A. Borden wrote:
>
> Now to your specific question, if objects are represented in this fashion,
> you can access members through interfaces (i.e. Java/C++) through get/set
> pairs. A language XML interface layer is needed. This layer is identical to
> COM's dispatch layer which allows COM objects to be used from within
> Javascript and VBScript. COM uses a binary typelibrary as input.

To a first approximation, a type library in COM corresponds to
a Java "Class" object. Both let you introspect on methods that
are exposed by objects, see interfaces and properties, invoke
methods, and so on. Used with JNI, you get inter-language calling.
(JNI uses "portable C" -- it's not OS-specific.)

> Our
> technique takes the SODL document and
>
> a) generates a typelibrary from it
> b) employs a custom interface which is driven by the SODL document
>
> The advantage of (a) is that it is compatible with existing software
> however the software is limited to Windows.

Building on that correspondence, one could apply this technique with
Java based systems. A specialized DTD could generate a class file.
Whoops, whoa, don't bother, just use the Java class in the first place...

That is, if you're content to be specific to a given platform (perhaps
Java, perhaps Win32/x86 :-) you can do some very interesting tricks.

BUT ... it may be desirable to design in a platform-neutral way. Not
to ding any particular platform (certainly not Java!); I just want to
point out that when using XML with Objects, there are lots of tradeoffs.

- Dave

> XML-DEV would be an excellent place to develop an independent (b) layer
> specification. This spec would certainly need to interface with DOM.