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Subject: Re: Porting Tuscany C++ to C++11 and some code cleanup
From: Thomas Gentsch <tg@e-tge.de>
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Date: Wed, 19 Dec 2012 22:00:01 +0100
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Hi JS,

I'm still looking through the docs, code, etc. I can find.

One thing I discovered: it does not look to me as if SDO support has
been removed from Java SCA, at least I found some related activity in
2011:

http://www.mail-archive.com/user@tuscany.apache.org/msg03435.html

http://www.mail-archive.com/dev@tuscany.apache.org/msg17116.html

(the latter is quite funny because I actually submitted this against C++
but seems as if the same problem occurred with Java? :-)

More later ... :-)
Rgds,
  tge

On Thu, 2012-12-06 at 01:04 -0800, Jean-Sebastien Delfino wrote:
> On Fri, Nov 30, 2012 at 9:43 AM, Thomas Gentsch <tg@e-tge.de> wrote:
>         
>         OK, many thx for this info!
>         
>         Regarding SDO - yes, I noticed that there was not a lot of
>         activity
>         during the last years.
>         Hello out there: Is there anybody else still using this?
>         
>         Rgd SDO as SCA-internal data-flow mechanism - what is being
>         used now?
>         I know about libxml2 (actually its being used in SCA/SDO :-),
>         nothing
>         yet about JSON, will read.
> 
> 
> Hi Thomas,
> 
> 
> Here's a short overview of what's used now.
> 
> 
> Data read/write functions are provided for XML (using Libxml2 [1]),
> JSON (using Mozilla SpiderMonkey but I've started to migrate to
> Jansson [2]), and Lisp/Scheme S-expressions [3].
> 
> 
> Here's how to read XML in a C++ component:
> <customer
> age="21"><name>johndoe</name><phone>(650)123-4567</phone><phone>(415)765-4321</phone></customer>
> 
> 
> // A list of strings containing the above XML doc, obtained from an
> input stream for example
> const list<string> ls = ...;
> 
> 
> // Read the XML doc (the failable<...> result type helps encapsulate
> error handling)
> // See below for a description of the 'value' data type
> const failable<value> fe = xml::readElements(ls);
> 
> 
> // Assuming no failure, get and print the result
> const value e = content(fe);
> cout << e << endl;
> 
> 
> The result is a list like follows (using the S-expression syntax here
> for conciseness: element, customer, attribute, age are symbols, 21 is
> a number, "johndoe" is a string, (x y) is a list of x, y):
> ((element customer (attribute age "21") (element name "johndoe")
> (element phone "(650)123-4567") (element phone "(415)765-4321")))
> 
> 
> The runtime is schema-less. You do not need an XML schema to
> read/write any XML.
> 
> 
> If you don't care about the XML element vs attribute representation
> you can strip it like this:
> const value v = elementsToValues(e);
> to get this:
> ((customer (@age "21") (name "johndoe") (phone ("(650)123-4567"
> "(415)765-4321"))))
> 
> 
> Note the @age attribute name, which follows the Badgerfish [4]
> convention often used to name XML attributes in JSON documents for
> example.
>  
> The same data can be constructed and represented in the various
> programming languages supported by the runtime, as follows:
> 
> 
> C++:
> list<value>(list<value>("customer", list<value>("@age", 21),
> list<value>("name", string("johndoe")), list<value>("phone",
> list<value>("(650)123-4567", "(415)765-4321"))));
> using the following C++ types:
> - string, similar to std::string but lighter and faster for small
> strings, with builtin conversions from/to native char*;
> - list<T>, a lightweight list/lazy-list type with useful
> Lisp/Scheme-like [5] functions incl. cons, car, cdr, map, filter,
> reduce, assoc, etc;
> - lambda<R(P...)>, a function type similar to std::function but
> lighter and faster;
> - value, a dynamic value type (type can be number, boolean, symbol,
> string, list<value>, lambda<value(list<value>)>, value*) with builtin
> conversions from/to native double, bool, char*, C++ lambdas and
> pointers.
> 
> 
> Python:
> ((customer, ("'@age" 21), ("'name", "johndoe") (phone,
> ("(650)123-4567" "(415)765-4321"))),)
> using Python tuples [6] and native Python data types for strings,
> numbers and booleans.
> 
> 
> JavaScript / JSON:
> {"customer":{"@age":"21","name":"johndoe","phone":["(650)123-4567","(415)765-4321"]}}
> using JSON arrays and native Javascript types.
> 
> 
> Scheme:
> ((customer (@age "21") (name "johndoe") (phone ("(650)123-4567"
> "(415)765-4321"))))
> just an S-expression.
> 
> 
> Java (there's experimental support for running Java components on the
> C++ runtime):
> list(list("'customer", list("'@age", 21), list("'name", "johndoe"),
> list("'phone", list("(650)123-4567", "(415)765-4321"))));
> using java.lang.Iterable [7] for lists and native Java data types for
> strings, numbers and booleans (the list(...) function is a static
> 'builder' function returning a java.lang.Iterable<?>.)
> 
> 
> To summarize: fast and schemaless support for XML, JSON and
> S-expressions, with lightweight representation using lists and simple
> types in the supported programming languages.
> 
> 
> Hope that helps.
> 
> 
> [1] http://www.xmlsoft.org
> [2] http://www.digip.org/jansson/
> [3] http://en.wikipedia.org/wiki/S-expression
> [4] http://badgerfish.ning.com
> [5] http://www.gnu.org/software/mit-scheme/documentation/mit-scheme-ref/Lists.html#Lists
> [6] http://docs.python.org/2/tutorial/datastructures.html#tuples-and-sequences
> [7] http://docs.oracle.com/javase/6/docs/api/java/lang/Iterable.html
> 
> 
> - Jean-Sebastien