7: Web Services Orchestration

Question 1

what is document centric interaction?

Answer 1

fill in a document, send it to someone who fills in a bit more, and passes it on

Question 2

what is the goal of web services?

Answer 2

aims to expose computational elements onto the web alongside data - to allow end-user programmer so that the user can generate complex actions

but the end user might not be good at programming, so we want to remove the complexity, and make it straightforward to tie services together

Question 3

what are orchestration and choreography? how do they differ?

Answer 3

orchestration:
allows a process to be described, and tells each component what do to do, when and to what
all decisions are provided by the orchestrating process
“programming for people focused on other things”

choreography is about the servies themselves building the process, communicating directly

Question 4

what is BPEL4WS?

Answer 4

Business Process Execution Language (for) Web
Services

a standard for orchestrating web services to define business processes

Question 5

describe the BPEL architecture/structure

Answer 5

leverages the web
a business process description is an XML document
uses business terms not computing terms
uses documents

a process has a number of partner links that provide services, WSDL interfaces onto SOAP endpoints
they are required for the service to function
can store variables to maintain state

Question 6

what is WSDL?

Answer 6

an XML format that describes a service, usually SOAP

Question 7

why is concurrency an issue? what’s teh solution?

Answer 7

it breeds complexity, which is what we’re trying to avoid.

dataflow: a style of computation that triggers activities based on the availablity of the data they need in order to complete e.g.
To book a trip I need a flight and a hotel
…and I won’t book without both
…but if I have both, then I can complete the booking

the component processes remain independant and then the task is only complete when all the required steps are complete. the execution engine can decide when to execute depending on availablity. removes the notion of invocation for the normies

Question 8

whats the advantage of using XML for BPEL?

Answer 8

easily auto generated