This is the essential benefit of a LINDA or some other kind of
publish-subscribe approach. Each object has two billboards, one stating what
they can do and the other what they need, etc.
The catch is how are these described (especially given that local tags have
only accidental global meaning). There are several obvious ways to get beyond
this that have their own levels of difficulties. And as David has pointed out,
getting people to make reasonable interfaces even for their own local needs has
not succeeded well.
But ...
Cheers,
Alan
>________________________________
> From: John Nilsson <[email protected]>
>To: Fundamentals of New Computing <[email protected]>
>Sent: Saturday, April 20, 2013 7:32 AM
>Subject: Re: [fonc] 90% glue code
>
>
>
>One approach I've been thinking about is to invert the "information hiding"
>principle.
>
>
>The problem with information hiding is that the interface and properties
>exposed by a module is determined by the module: "I am a..." And some line is
>drawn between which properties are implementation details, and which are the
>contract.
>
>So I was thinking, what if the roles were swapped. What if modules could not
>declare a public contract but instead just had to conform to any type,
>interface or property that a client depending on it would care to declare as a
>requirement. In effect changing the module description into a collection of
>"You are a..." statements. Kind of similar to how a structural type allow any
>module conforming to the interface without the module having to implement a
>particular nominal type.
>
>For one, declaring a contract for a dependency is rather easy as it is based
>on local reasoning: "What do I do, what do I need?" as compared to "What do I
>do, what do others need?"
>
>Another benefit would be that there is no arbitrary reduction of the modules
>full capabilities. For example a Java List only implementing Iterable couldn't
>be used by clients requiring an ordered and finite sequence.
>
>I would expect this to encourage module writers to declare the smallest set of
>properties possible to depend on so that there would be more focus on
>"information shielding", what information to expose one self to, rather than
>what information not to expose to others.
>
>
>
>The problem with this approach is that the proof of conformance can't come
>from the module, and it's hardly productive to require each client to provide
>one. I guess in some sense this is partly solved by a mechanism such as type
>classes as done in Scala or Haskell. One problem with this scheme though is
>that they do this by means of a static dispatch, making it impossible to
>specialize implementations by runtime polymorphism. While I haven't played
>with it, I do believe that Clojure has solved it while preserving runtime
>polymorphism.
>
>
>
>
>BR,
>John
>
>
>
>
>On Thu, Apr 18, 2013 at 3:13 AM, David Barbour <[email protected]> wrote:
>
>Sounds like you want stone soup programming. :D
>>
>>
>>In retrospect, I've been disappointed with most techniques that involve
>>providing "information about module capabilities" to some external
>>"configurator" (e.g. linkers as constraint solvers). Developers are asked to
>>grok at least two very different programming models. Hand annotations or
>>hints become common practice because many properties cannot be inferred. The
>>resulting system isn't elegantly metacircular, i.e. you need that
>>'configurator' in the loop and the metada with the inputs.
>>
>>
>>An alternative I've been thinking about recently is to shift the link logic
>>to the modules themselves. Instead of being passive bearers of information
>>that some external linker glues together, the modules become active agents in
>>a link environment that collaboratively construct the runtime behavior (which
>>may afterwards be extracted). Developers would have some freedom to abstract
>>and separate problem-specific link logic (including decision-making) rather
>>than having a one-size-fits-all solution.
>>
>>
>>Re: In my mind "powerful languages" thus means 98% requirements
>>
>>
>>To me, "power" means something much more graduated: that I can get as much
>>power as I need, that I can do so late in development without rewriting
>>everything, that my language will grow with me and my projects.
>>
>>
>>
>>
>>On Wed, Apr 17, 2013 at 2:04 PM, John Nilsson <[email protected]> wrote:
>>
>>Maybe not. If there is enough information about different modules'
>>capabilities, suitability for solving various problems and requirements, such
>>that the required "glue" can be generated or configured automatically at run
>>time. Then what is left is the input to such a generator or configurator. At
>>some level of abstraction the input should transition from being glue and
>>better be described as design.
>>>Design could be seen as kind of a gray area if thought of mainly as picking
>>>what to glue together as it still involves a significant amount of gluing ;)
>>>But even design should be possible to formalize enough to minimize the
>>>amount of actual design decisions required to encode in the source and what
>>>decisions to leave to algorithms though. So what's left is to encode the
>>>requirements as input to the designer.
>>>In my mind "powerful languages" thus means 98% requirements, 2% design and
>>>0% glue.
>>>BR
>>>John
>>>Den 17 apr 2013 05:04 skrev "Miles Fidelman" <[email protected]>:
>>>
>>>
>>>So let's ask the obvious question, if we have powerful languages, and/or
>>>powerful libraries, is not an application comprised primarily of glue code
>>>that ties all the "piece parts" together in an application-specific way?
>>>>
>>>>David Barbour wrote:
>>>>
>>>>
>>>>>On Tue, Apr 16, 2013 at 2:25 PM, Steve Wart <[email protected]
>>>>><mailto:[email protected]>> wrote:
>>>>>
>>>>> > On Sun, Apr 14, 2013 at 1:44 PM, Gath-Gealaich
>>>>> > In real systems, 90% of code (conservatively) is glue code.
>>>>>
>>>>> What is the origin of this claim?
>>>>>
>>>>>
>>>>>I claimed it from observation and experience. But I'm sure there are other
>>>>>people who have claimed it, too. Do you doubt its veracity?
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Apr 15, 2013 at 12:15 PM, David Barbour
>>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>>
>>>>>
>>>>> On Mon, Apr 15, 2013 at 11:57 AM, David Barbour
>>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>>
>>>>>
>>>>> On Mon, Apr 15, 2013 at 10:40 AM, Loup Vaillant-David
>>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>>
>>>>> On Sun, Apr 14, 2013 at 04:17:48PM -0700, David
>>>>> Barbour wrote:
>>>>> > On Sun, Apr 14, 2013 at 1:44 PM, Gath-Gealaich
>>>>> > In real systems, 90% of code (conservatively) is
>>>>> glue code.
>>>>>
>>>>> Does this *have* to be the case? Real systems also
>>>>> use C++ (or
>>>>> Java). Better languages may require less glue, (even
>>>>> if they require
>>>>> just as much core logic).
>>>>>
>>>>>
>>>>> Yes.
>>>>>
>>>>> The prevalence of glue code is a natural consequence of
>>>>> combinatorial effects. E.g. there are many ways to
>>>>> partition and summarize properties into data-structures.
>>>>> Unless we uniformly make the same decisions - and we won't
>>>>> (due to context-dependent variations in convenience or
>>>>> performance) - then we will eventually have many
>>>>> heterogeneous data models. Similarly can be said of event
>>>>> models.
>>>>>
>>>>> We can't avoid this problem. At best, we can delay it a
>>>>> little.
>>>>>
>>>>>
>>>>> I should clarify: a potential answer to the glue-code issue is
>>>>> to *infer* much more of it, i.e. auto-wiring, constraint
>>>>> models, searches. We could automatically build pipelines that
>>>>> convert one type to another, given smaller steps (though this
>>>>> does risk aggregate lossiness due to intermediate summaries or
>>>>> subtle incompatibilities). Machine-learning could be
>>>>> leveraged to find correspondences between structures, perhaps
>>>>> aiding humans. 90% or more of code will be glue-code, but it
>>>>> doesn't all need to be hand-written. I am certainly pursuing
>>>>> such techniques in my current language development.
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> fonc mailing list
>>>>> [email protected] <mailto:[email protected]>
>>>>> http://vpri.org/mailman/listinfo/fonc
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> fonc mailing list
>>>>> [email protected] <mailto:[email protected]>
>>>>> http://vpri.org/mailman/listinfo/fonc
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>_______________________________________________
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>>>>>
>>>>
>>>>--
>>>>In theory, there is no difference between theory and practice.
>>>>In practice, there is. .... Yogi Berra
>>>>
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>>>
>>
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