21. Services over the web Flashcards
Inherently Distributed Systems
How does the distributed web make it easier to create applications?
All nodes provide services. To build an app we can utilize services on different nodes (servers)
Describe MIMD
Shared nothing
When can we characterise distributed computing as MIMD parallel computing
When the interconnect is network scale
How do we break up code and data
A = A1 = A2 each piece of code is the same D = union of d1 d2 etc. Instances act as a partition of the data set
What is the problem when the code in each machine is different and the data are not partitions of a single data set? What is the solution?
Difficult to parallelize. Service space computing- using whats available on the net to help us distribute
How do we virtualizing entire business processes?
Integrate intranet and extranet applications using a business to business integration system
What processes are there in supply chain management
Customer response
Order processing
Order fulfillment
Invoice and payment
What is a rich internet application?
Run in web browser. Rely in asynchronous Java script to provide the look and feel of desktop applications to distributed systems
E.g. Gmail BBC iPlayer
What is a web mashup?
Lightweight web application that combines processing and data resources from different sources into a single integrated application.
Relies on asynchronous Java script
How do we access a service
Call it
How do we access a resource?
Describe it
How do we integrate?
RPC
What is ws-*
Alternative to rest
View that the web is a foundation over which one can add a software layer for distributed computing
Components behind URIs interact using a higher up protocol. State is on a different server
What is the REST view of web services?
REST: representational state transfer
The web is a distributed computing engine. Keep state on the server
Interactions using http verbs
Components behind URIs remain http servers
When do we use ws-*
EAI and B2B systems that virtualize coarse grained processes
Steps naturally interrelated (order dependent or shared state)
Characteristics naturally expressed in remote method invitation paradigm
