Web Services Members Troy Tony Ellen Vincent

Web Services What is it Why is it useful What have been solved Demo Alternative technologies Question

What is Web Service An XML technology which allows an application to access a remote/local application’s services with very little code customization using ubiquitous and standard communication protocols. Standard Package: 1.WSDL 2.UDDI 3.SOAP

How Does It Work?

Why Web Service Useful “ you can exchange data between different applications and different platforms” (quoted from W3Schools.com) for the following reasons: 1.It is platform independent 2.It is language independent 3.It uses one of the most popular ways for data communication – XML 4.Enabling the reuse of software components 5.Delivers a loosely coupled architecture (e.g. SOA)

What have been solved? Technical point of view: Platforms / development languages conflict Business point of view: enabling data exchange among different business partners while each one of them may use different types of servers/languages

Web Service in the Real World LiveJournal - Blog Management Google Map / Geocoding PayPal Protein Data Bank

Limitations of Web Service Draw Back: 1.Once implemented, no control in response time of the service 2.XML (SOAP, WSDL) is easy for human (programmers) to read but have poor processing performance 3.Have no way to know how the clients will use the result from the web service. This limits the type of the data analysis/mining that can be performed.

Demo Python (install fpconst, SOAPpy) Perl

Web Services Demo Python import SOAPpy import random server = SOAPpy.SOAPServer(('localhost', 8080)) server.registerFunction(numberGenerator) def numberGenerator(): list = range(1,50) lo_nums = [] i = 0 while i < 6: number = random.choice(list) if (number != -1): lo_nums = lo_nums + [number] list[number-1] = -1 i = i + 1 return lo_nums server.serve_forever() Link to Demo Perl use SOAP::Transport::HTTP; use strict; SOAP::Transport:: -> dispatch_to(‘Lottery') -> handle; package Lottery; sub lotteryNumbers { my ( $val, $seed) $seed ? srand $seed : srand; = ( ); while < 6 ) { my $n = int ( $pools[0], $pools[$n] ) = ( $pools[$n], $pools[0] ); } return }

Alternative Technologies MQ Series (from IBM) –Multi-platform and multi-language message queuing service –Asynchronus One program queues messages Another program processes messages Managed by a Queue Manager; actions are event triggered –Two types of queue connections (called channels) 1) Unidirectional and 2) Bidirectional –Applications can be loosely coupled with MQ Series but they must be contained within a cooperating system since connections are pre-established and static.

Alternative Technologies

MQ Series (continued) –Strengths Support for multiple platforms Well tested and generally considered stable Simplifies inter-application communications Workflow management and load balancing Queuing –Weaknesses Message based rather than object based Not stateful or persistent Hard wired channels (communication links between apps) Location is not transparent requiring more management

Alternative Technologies CORBA (Common Object Request Broker Architecture) –Platform and language independent –Object oriented component architecture –Stateful & persistent –Flexible features to decouple the client and object implementation –Performance is good enough for real-time applications –Support for transactions, security and events notification. –E.g. Linux Gnome – a network centric graphical user interface.

Alternative Technologies

CORBA (continued) –Stengths Platform independent (as long as there is vendor support) with multi-language support Stateful and persistent objects Widely deployed today Integrated security services including its own naming service that minimizes the risk of spoofing, etc. Service discovery –Weaknesses Fairly complex to configure and implement Not standardized for today’s network security issues. Not organized for easy integration with web apps

Alternative Technologies DCOM (Distributed Components) –Object oriented –Objects are stateful, persistent, can pass data, event driven, … –Seamlessly connects local and remote COM objects into a running process (e.g. transparent use of remote objects) –Tightly interacts with ActiveX for web deployment and OLE. –Primarily Windows. Microsoft support for MacOS and third party support for some UNIX (although UNIX COM not supported by developers thus very limited services) –Early issues regarding security, complexity, load balancing and others making it unsuitable for enterprise deployment. COM+ and Microsoft Transaction Server (MTS) attempted to fix

Alternative Technologies COM Object Access

Alternative Technologies COM (continued) –Strengths Multi-language support (kind of) It doesn’t care where the object is sourced from Statefulness, persistence, native data transfer and event capabilities (e.g. exceptions) Relatively mature technology –Weaknesses Platform dependent (platform must understand binary format) Supports COM-aware languages only Considered by many complex to develop and maintain

Our Comments What is cool… Troy: “Loosely coupled architecture” Vincent: “Free” Tony: “Code Reuse” Ellen: “Compatible”

References

Questions?