Re: [HiveMind] Basic questions about Service

[Christian Essl]

I still mean a - traditional - database provides a good (better) service. 
The reasons for this are the semantic and pragmitical levels of information 
which are very influenced by the way the underlaying data is used. An OO- 
database as I see binds to early the functionality to the data and 
therefore restricts the potential semantic and pragmitcs of the data. In a 
traditional DB the data interrelations are given not until the query. A 
direct result of that is that it is easy to move data from one domain to 
another, to do data-mining etc. As said what is functional and what is a 
good service depends on what the user finds functional. There is no common 
standard like there is no standard in a market-economy (contrary to a 
communistic world) that says this shoe-color is good and that bad.

Apart of this for me Services and Service-Archticture are rather a question 
of software-design philosphy and not so much of programming-technology. As 
I see these design questions are a bit above (or beside) the OO thing. I 
think services can be better compared to concepts like frameworks, (plugins 
in ) plugin-architcture etc than to OO. And all thinks like that can be 
implemented with or without OO.
  On Thu, 25 Sep 2003 00:36:06 -0400, Harish Krishnaswamy 
<[EMAIL PROTECTED]> wrote:

I agree with all your points except the database example. A database, if 
built respecting OO principles, should bundle its metadata and its 
funtionality/behavior into classes that provide the service; the user 
data is aside the point.

-Harish

Christian Essl wrote:

I think thats realy an intresting question. I mean I don't realy know 
but I think - as you do - a Service provides a specific functionality. 
However I am not sure wheter this must always be data-hiding - just look 
at a database, which provides a good service. I also believe that one of 
the first ideas of OO was that you build big systems out of a number of 
robust small peaces which have a well defined cloased interface so that 
they can evolve independently. That's certainly what services (at least) 
in HiveMind are. Another idea I think was that the small pieces can work 
together without the need of a central main-component, so that new 
combinations can be build flexible. And last I think there is also a 
notion of competition on ideas on how to provide a better service to the 
user - without centralized normativ control. It is up to the user (and 
anyone can be user) what he needs and what service he uses and it is up 
to the service to provide well what it promisses - and if it is just 
data.

On Wed, 24 Sep 2003 21:39:16 -0400, Harish Krishnaswamy 
<[EMAIL PROTECTED]> wrote:

I am a little confused now. I am confused as to what the boundaries of 
a service are. Is there even a distinction between a Service and a 
domain object? I start seeing people actually suck out the behavior of 
domain objects into services and have the domain object as a simple 
JavaBeans data object. I literally saw an example that had an Employee 
object which represented the database table and an EmployeeService 
which represented the behavior for the Employee object. To me this 
sounds like its against the principles of OO (assign the responsibility 
to the information expert). So this leads to a more basic question - 
what is a Service? I think we need a technical definition for Service. 
I thought of the Service as an interface to a subsystem / a specific 
function. Am I missing something?

-Harish



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