Presentation (discussant)

warbarnacleΑσφάλεια

5 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Turning Software into a Service


The Critique

Paul Kopacz

Brian Moore



Dynamic Composition


Heavy emphasis


“...we seek to devise a suitable mechanism for
creating new forms of service on demand”


“...lets the set of services a business uses evolve
without any user interaction as the business and it's
context change”


The most interesting idea in their paper

Is Dynamic Composition Possible?


They hope so


No references to studies


No limits imposed on composition


No details on what composition will do


No Silver Bullet

by Fred Brooks


"I believe the hard part of building software to be
the specification, design, and testing of this
conceptual constr
uct”


How much of this work can be done
automatically?

What is Composition Based on?


Possible standards


DAML
-
S


Not complete


BPEL4WS


Not dynamic


“Providing this capability will require support
from high
-
bandwidth information networking”


They expect it will be provided

Composition


The Question


Can you propose an approach based on
unfinished standards?


What if the standards never work?


Unproven and untested with real applications

Adoption of Technology


Widely used standards inadequate


The most complete stack is based on ebXML


e.g. Contract negotiation


Semantic Web technology


DAML
-
S (now OWL
-
S)


Describe semantics of services, “what they actually
do”


Even these are lacking

Adoption of Technology


Semantic Web and ebXML based technology
not widely used in industry


They are highly complex


The authors need them to be more complex


Can regular developers use these
technologies?


“Small
-
scale specialist
-
services providers”


Will smaller development firms have the resources?

Online Service Vendors


“Such a model would open up new markets”


Assume functionally identical services from
multiple providers


Various choices for services to compose from


Vendors differentiate based on non
-
functional terms
(price, reliability, speed, etc.)

Online Services Today


Internet enables worldwide competition


Mature markets contain small numbers of
players


Most successful remain


Smaller companies differentiate based on
functionality


Big market examples


Search has three dominant companies


Online auctions has one

Finding Online Services


As markets mature, number of choices
decrease


Will automatic binding still work with services
differentiated based on functionality?


Does it even make sense to do this?


Is their complex model necessary?

Security and Reliability


“...because it concentrates instead on other
areas, our current model does not include
security”


Design with security in mind


Little discussion of possible failure


Only transactions are mentioned


Other types of failure are not mentioned

Failure


You are providing a service with other peoples'
code


Why should you trust it?


How do you make sure it behaves as advertised?


This is all done dynamically


Dynamic error checking?


Who do you trust?

Programming and the Web


“...the basic paradigm for constructing and
maintaining software has altered little since the
1960s.”


Edit
-
compile
-
link procedural source code into a
binary


“...the practices used to develop and implement
a Web site differ little from those traditionally
employed for constructing software and are just
as error prone.”

Programming and the Web


Web programming is where the departure is
most evident


J2EE containers


Scripting/Interpreted languages


Composition and pipelining


Ignoring what is currently being done