Web Services

Web Services

Sabesan

Uppsala Database Laboratory Dept. of Information Technology

Uppsala University Sweden

Service Oriented Architecture

Service Registry

Service

Requestor Service

Provider Bind

Find Publish

 Service provider: responsible for creating service description and deploying the service.

 Service registry: responsible for publishing the service description

 Service requetsor : responsible for finding a service decription to consume the service

Web Service basics

 A software system designed for supporting machine-to-machine interaction over a network.

 A collection of related operations that are accessible over a network.

 Opearations are described by a service description document.

 Based upon the open standard technologies such as XML, WSDL, SOAP, UDDI

XML- Extensible Markup Language (XML) is a general-purpose specification for creating custom markup languages.

SOAP- Simple Object Access Protocol for exchanging structured information

WSDL- Web Service Description Language is an XML based description language for web services.

UDDI - Universal Description, Discovery and Integration (UDDI) is a platform-independent, XML- based registry for businesses worldwide

Databases PDM LKAB

Size of Iron pellet ?

Query

Web Service

Web Service Scenario

•A Web service is a software system designed to support interoperable machine-to-machine interaction over a network.

• It has an interface described in a machine-processable format (specifically WSDL).

•Other systems interact with the Web service in a manner prescribed by its description using SOAP messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web- related standards

Web service is defined by W3C (

) as:

Publicly available Web services

1. Google web service 2. Amazon web service

3. Terraservice web service – Microsoft

www.xmethods.net – provide information about the publicly available web services

Key reasons for deploying a web service

1. Scope of problems addressed :- CORBA focused on technical architectures rather than problems of application integration.

 Support both document centric messaging and remote procedure calls

 Transport encoded data from both applications and business documents

 Work with standard internet protocols such as HTTP and SMTP

2. Using existing standard core technologies: XML, SOAP, HTTP

3. Industry Dynamics: Customer needs, market pressure, and the desire to be the partner of the up-to-date trends

Discovery : UDDI Description: WSDL Message packaging: SOAP Communication: HTTP

Web Service Architecture

 Service discovery: a dictionary of web services

 Interface description: describes how to call operations of a web service

 Message packaging: formats the data ready for communication

 Communication layer: transports data over network

Web Services Description Language(WSDL)

 WSDL uses XML for describing services

 WSDL describes:

• What operations are provided

• How operations are accessed

• Where a service is located

Header

SOAP block SOAP block Envelope

Body

SOAP block

SOAP block

Simple Object Access Protocol (SOAP)

• SOAP header provides a mechanism for adding features to the message such as routing and delivery setting, authentication assertions, and transaction contexts

• SOAP body contains the actual message to be delivered and processed

 It is difficult to find data provided by web services:

Current web services applications must be developed using a regular programming language such Java, C# .

 To simplify searching web services data:

We propose efficient processing of database queries to views of wrapped web services.

Our Problem Area

WSMED

SOAP

Our Approach- Web Service MEDiator (WSMED) Architecture

WSDL

Web Service

Development of WSMED, a web service based mediator prototype :

Query ^Result

WSMED System

Local

store WSMED

OWF₁ OWF_n

WO₁ WO_n

WSDL descriptions

14

Research Issues

1. How can standards, such as WDSL, SOAP, and XML- Schema, be automatically utilized by a mediator engine?

2. How can database views be defined in terms of imported web service descriptions?

3. How can the modern query optimization be used to provide efficient access to wrapped web services?

4. What minimal set of extra semantic enrichment is needed to provide efficient queries ?

5. How speedup the queries with dependent web service calls ?

WSMED View

ndb keyword descry gpcode

19080 Sweet Candies, Sweet chocolate 1900

………. ……… ………… ……….

Food

select descry from food

where gpcode = ’1900’ and keyword = ’Sweet’;

SQL Query:

Service ports Operation

input output

M

N

M SearchFoodByD

escription

N

Element

sub 1

elements

string

N

NDBNumber

1

N

document

http://schemas.xmlsoa p.org/soap/encoding/

http://ws.strikeiron.com /StrikeIron/USDAData

http://www.strikeiron.com/

SearchFoodByDescription USDAData

1

Web Service Schema

Web service schema can represent any WSDL document that describes a web service

http://www.strikeiron.com/

Web Service MEDiator System Architecture

 WSDL importer: extracts meta data from WSDL document using Web Service Schema and store them in the Web service meta-database

 Web Service Manager: invokes the web service operation to retrieve the data

 WSMED enrichments: contains the semantic enrichments WSDL

Importer

Web service Manager

SQL query Query

Processor

WSMED enrichments Web service

Schema

Web service Meta-database

Results Web

Service WSDL

document

web service arguments SQL query

query rewriter

cost-based optimizer execution

engine calculus

generator

view expander

Comparison of query execution strategies

0.00 1000.00 2000.00 3000.00 4000.00 5000.00 6000.00

0 100 200 300 400 500 600 700 800 900

Number of Food Items

Response Time(sec)

full semantic enrichment hashjoin strategy

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00

0 100 200 300 400 500 600 700 800 900

Numbe r of Food Ite ms

Response Time(sec)

hash join strategy full semantic enrichment

WSMED Process Tree

q- query processes Level 2

q0

q1

q3 q4

q2 GetPlacesWithin

GetAllStates

GetPlaceList

q5 q6 q7 q8

Coordinator Level 1

Query1

Finds information about places located within 15 km from each city whose name starts with ’Atlanta‘ in all US states.

Observation –Query1

1 4 5 6 10 15 20 25 30 40 60 0 3

5 11 100

2030 4050 6070 8090 100110 130120 140150 170160 180190 200210 220230 240250

Execution time

f1

f2

50-60 60-70 70-80 80-90 90-100 100-110 110-120 120-130 130-140 140-150 150-160 160-170 170-180 180-190 190-200 200-210 210-220 220-230 230-240 240-250

• Lowest execution time region is achieved within the range 50 - 60 sec with the fanout vector {5,4}.

• Fastest execution time 56.4 sec outperformed with the speedup of 4.3 the central

Adaptive Results- Query1

Query1

0.00 20.00 40.00 60.00 80.00 100.00

Process selection

Execution time

Best FF_APPLYP fo1=5 fo2=4 p=1, no drop stage, fo1=3 fo2=3 p=1, drop stage, fo1=2 fo2=3 p=2, no drop stage, fo1=4 fo2=5 p=2, drop stage, fo1=3 fo2=3 p=3, no drop stage, fo1=5 fo2=3.4 p=3, drop stage, fo1=4 fo2=3.25 p=4, no drop stage, fo1=6 fo2=8.7 p=4, drop stage, fo1=5 fo2=4.2 p=5, no drop stage, fo1=7 fo2=7.5 p=4, drop stage, fo1=6 fo2=7.8

Semantic Web Services

•An emerging framework that aims at machine-processable information for information sharing.

•Defines standards not only for syntactic form of documents, but also for the semantic contents

•RDF /RDFSchema to facilitate semantic interoperability

•An ontology defines a hierarchy of concepts within a domain through an attribute-value means

Resource Description Framework (RDF)

• RDF provides a method to decompose any knowledge into small segments, called triples

• Each triple contains subject, object and predicate.

http://www.it.uu.se/edu/ course/kursstart/spring.html

http:/ /www.it.uu.se/edu/ Department of Information Technology

http://www.it.uu.se/edu/maintained

Questions ???

Thanking You for the attention

“The un-queried life is not worth living”