Blue Sky - Web Services

Bruce SpencerBRWS Group MeetingApril 18ITC 307

“The Semantic Web” T. Berners-Lee et. al, Scientific American, May 2001

The entertainment system was belting out the Beatles’ “We Can Work It Out” when the phone rang. When Pete answered, his phone turned the sound down by sending a message to all the other local devices that had a volume control. His sister, Lucy, was on the line from the doctor’s office: “Mom needs to see a specialist and then has to have a series of physical therapy sessions. Biweekly or something. I’m going to have my agent set up the appointments.” Pete immediately agreed to share the chauffeuring. At the doctor’s office, Lucy instructed her Semantic Web agent through her handheld Web browser. The agent promptly retrieved information about Mom’s prescribed treatment from the doctor’s agent, looked up several lists of providers, and checked for the ones in-plan for Mom’s insurance within a 20- mile radius of her home and with a rating of excellent or very good on trusted rating services. It then began trying to find a match between available appointment times (supplied by the agents of individual providers through their Web sites) and Pete’s and Lucy’s busy schedules. (The emphasized keywords indicate terms whose semantics, or meaning, were defined for the agent through the Semantic Web.)

 

In a few minutes the agent presented them with a plan. Pete didn’t like it—University Hospital was all the way across town from Mom’s place, and he’d be driving back in the middle of rush hour. He set his own agent to redo the search with stricter preferences about location and time. Lucy’s agent, having complete trust in Pete’s agent in the context of the present task, automatically assisted by supplying access certificates and shortcuts to the data it had already sorted through.

 Almost instantly the new plan was presented: a much closer clinic and earlier times—but there were two warning notes. First, Pete would have to reschedule a couple of his less important appointments. He checked what they were—not a problem. The other was something about the insurance company’s list failing to include this provider under physical therapists: “Service type and insurance plan status securely verified by other means,” the agent reassured him. “(Details?)”

 Lucy registered her assent at about the same moment Pete was muttering, “Spare me the details,” and it was all set. (Of course, Pete couldn’t resist the details and later that night had his agent explain how it had found that provider even though it wasn’t on the proper list.)

Vision of BRWS

• Web services will be the glue that ties applications to users and applications to applications– Subsumes existing software architectures

• Stand-alone, component-based, thin client, fat client, multi-tiered, multi-agent system …

– Software interfaces published in machine-understandable ways

Vision of BRWS:

• Rules for business processes customize web services to meet the demands of particular applications

• Rule-based computations • Justification and Explanation services

– Why did it give me this answer? – Why not this other answer?

• Conditions and actions are parts of rules – Sensors and Effectors– Conditions to invoke rules– Actions taken when some conclusion is found

Example 1: Price Quote Service

• Buyer requests price from seller• Rules express pricing policy.• Quote depends on customer, order date, delivery

date, purchase history, order size, strategic policy, …

• Quote server runs on seller’s site

Price Quote Rules

discount(V0,V1,'5.0 percent')<-premium(V0),regular(V1).

discount(V0,V1,'7.5 percent')<-premium(V0),luxury(V1).

premium(V0)<-spending(V0,'min 5000 euro','previous year').

luxury('Porsche').regular('Honda').spending('Peter Miller','min 5000 euro','previous year').

Price Quote Proof

discount(Peter Miller,Honda,5.0 percent)<- premium(Peter Miller)<- spending(Peter Miller,min 5000 euro,previous year)<-. regular(Honda)<-.

Web Services

• Loosely coupled Software components– Interfaces described by UDDI and WSDL

• UDDI –universal description, discovery and integration– Global business registry– Retrieval by names, by categories, by service types, or– tModelKey- unique number ascribed to the server

• 16 bytes based on MAC address and the time of day

SOAP

• Simple object access protocol• Simple request and response• Messages (payloads) are XML• Platform neutral

WSDL

• Web Services Description Language• All the information you need to use a web

service• Allows integration

– Automatic?• Methods, argument types, return values

UDDI

• Universal Description, Discovery and Integration• Global electronic yellow pages of web services• Each service has a unique 16 byte number• Each service has a published description• Service discovery quick, followed by easy use of

services• Loose coupling

Example 2: Privacy Service

• Requestor requests personal info from owner• Rules express privacy policy of owner• Access depends on requestor, digital signature,

intended use of information, sharing policy of requestor, requestor’s history

• Privacy server runs where private information resides

Example 3: Immigration Application Service• Potential immigrant requests confirmation of

data required for visa application• Rules express immigration department’s policy

for visa application• Visa application complete if all required personal

data received• Server runs on immigration department’s

website

Example 4: “Explanation” service

• A service provided to users of any rule-based web service (meta-service)

• Rules express some policy of interest– Why did I get a 5% discount?

• Tree structure that represents the proof– Why did I not get a 7.5% discount?

• Shows the rules that might have applied• Why each failed

– Generates confidence in other web services if they are rule-based

Other ideas

• Asynchronous web services