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Web Services
Contents
What are Web Services?
How do web services work and who uses them?
Where are web services being used?
What issues are there with web services?
What are the standards relating to Web Services?
What are the implementation issues?
Other sources of information
What are Web Services?
The web has grown massively over the past decade and now features heavily in our daily use of
computers. During this period we have seen significant advancements in how web pages are
designed and viewed. Despite these developments, however, our use of the web remains quite
static and labour intensive.
For example, a person wishing to buy stationery over the web still has to search different
stationery suppliers’ web sites and, in most cases, manually compare the prices before ordering
from one chosen supplier and arranging for delivery.
Web services (WS) are concerned with enabling systematic application-to-application
interactions over the web and with integrating existing network computer infrastructure into the
web. Using the example of stationery suppliers, web services technology would allow the same
person to compare the prices of stationery on one site and enable him/her to order from the
chosen supplier dynamically.
How do web services work and who uses them?
Before discussing how web services work it is worth defining the different types of users. Note
that the following definitions are not necessarily industry standard terms but are used here to aid
with the understanding of WS.

The web service provider: writes the code and applications for other WS users.

The web service consumer: uses the applications and code produced by the WS
provider. There could be two types of WS consumer:

© Becta 2004
o
The web service broker: consumers that provide a brokerage for the day-today web user. For example, a travel agency allowing different holidays and
flights to be compared and then booked all on the same web site.
o
The independent web service consumer: has a direct relationship with the
WS provider. The relationship between the WS provider and independent
WS consumer is perhaps the major relationship that will be seen for WS use
in the next few years. Most likely to be between two or more commercial
organisations rather than home web users.
The web service end user: although the end user is not using a WS directly,
he/she is part of the WS chain of events. Someone booking a holiday on the
travel agency web site, for example, would be using a Web Service, though they
are unlikely to notice any difference in their use of the web.
Valid at September 2004
Review at December 2004 – Archived in April 2006
page 1 of 5
Becta | Technical paper | Web services
Web Service
Providers
Web Service
Consumers
Company A
Company B
Independent
user
Broker
Web Service
end users
Figure 1: Associations between different users of Web Services
The interactions that take place between a WS provider and WS consumer are standardized
using eXtensible Mark-up Language (XML)-based messages.
In brief, a WS consumer sends a message over the Internet to a WS provider with whom he/she
wants to interact.
From a WS provider’s point of view some development work will need to be done either to design
a new WS or expose an internal legacy service as a WS.
From the consumer’s point of view, tools are being developed that will be able to create WS
messages. This will keep the underlying technical aspects hidden from the consumer.
Directories of Web Services are beginning to appear in which providers store details of their
service and how to interact with it, however they are not particularly advanced as yet. The idea is
that consumers will be able to find a service by searching the directory in a similar way to
electronic yellow pages services.
© Becta 2004
Valid at September 2004
Review at December 2004 – Archived in April 2006
page 2 of 5
Becta | Technical paper | Web services
The following diagram shows, at a high level, the interactions that need to take place in order to
use a WS.
Web Service Provider
Web Service Directory
Uses the web service
(knows already how to
interact with it)
Result from
the web service
x
es it
do with
t
a t
th c
e era
vic int
r
se to
b ow
we h
a ow
nd h
Fi d s
an
Web Service Consumer
For future
development
Figure 2: Basic interactions between a Web Service consumer and a Web Service provider
Major software providers are building platforms and application software that should make the
development and consumption of WS relatively simple. There are currently two main
implementation platforms for WS – Microsoft's .NET and Sun's J2EE.
Microsoft’s .NET solution aims to have built-in applications allowing users to interact seamlessly
with WS. Other suppliers, such as Oracle, are basing their WS software on J2EE.
As WS messages are based on defined standards, the theory is that any platform and WS
application should be able to interact with another manufacturer’s platform and software. It
remains unclear, however, how interoperable the different WS solutions will be.
Where are web services being used?
In general, WS using the full range of technology, including directory services, are not yet being
used. However, some commercial web sites are starting to use a scaled-down version of the
services.
One example is the on line retailer Amazon [http://www.amazon.com/]. This company (as the WS
provider) now allows other suppliers to access its databases of goods from their own web sites
(as WS consumers). In this way, one supplier could use their web page to check Amazon and
another book supplier for the best price on a book, saving the WS end user the trouble of having
to do the same process manually.
Although these types of services are starting to appear, WS has not yet made an impact on
individual schools. WS will become most prevalent between business organisations, although it is
possible that Local Authorities could offer web services as a means of data gathering from
appropriate institutions and may interact with businesses, such as educational suppliers, offering
a WS.
© Becta 2004
Valid at September 2004
Review at December 2004 – Archived in April 2006
page 3 of 5
Becta | Technical paper | Web services
What issues are there with web services?
As already mentioned, WS architecture and software are really in their infancy. As such, there are
many issues concerning their use and implementation that accompany the advantages. Below is
a list of some of the positive and negative aspects of WS:

WS can save time doing tasks which usually require a lot of manual inputting, for
example comparing prices from a number of suppliers using their web sites and
then inputting contact details each time an order is placed.

WS will enable systems in different organisations to interact with each other using
defined communication standards.

WS should mean there is no need for complete and costly integration solutions
when an application on one computer needs access to an application on another
computer outside of its network.

An upgrade/change to an application on one computer or a move to another
platform should not affect how a consumer interacts with a particular WS.

Present firewalls cannot filter on a content level ie, look at the XML. Therefore, an
XML firewall application may be needed to increase network security when WS are
developed or consumed.

It will be several years at least before the proposed universal service directory(-ies)
benefits the WS consumer in education.

It is unlikely, at least in the short term, that many WS will be provided for free to
consumers.

A computer that is turned off or suffering problems will not be able to supply a
service; this will affect organisations that rely on the consumption of WS.
What are the standards relating to Web Services?
XML
http://www.w3.org/TR/REC-xml
an extensible web language, far more powerful and versatile than HTML.
SOAP
http://www.w3.org/TR/soap12-part1/
an XML-based message wrapper providing a simple and consistent mechanism for sending a WS
request or reply.
WDSL
http://www.w3.org/TR/wsdl20/
an XML-based standard which describes what functionality a WS offers, how to communicate
with it and where it is accessible.
UDDI
http://www.uddi.org/
an XML-based standard which provides a universally accepted way for WS to be found on the
Internet.
What are the implementation issues?
There are several issues to consider when implementing and consuming WS including:

© Becta 2004
the choice of platform and the applications from which WS are implemented and
consumed
Valid at September 2004
Review at December 2004 – Archived in April 2006
page 4 of 5
Becta | Technical paper | Web services

the interoperability of a particular WS over different platforms may need to be
checked before commitments to a WS or WS platform/application software are
made

to be a regular provider or consumer of a WS the supporting infrastructure, such as
network connections and web servers, needs to be robust and reliable

it is likely that some software expertise will be needed to implement useful and
reliable WS

some consideration will need to be given to whom the WS interaction is with. A
provider will most likely want some way of checking things such as the credit rating
and integrity of a consumer. A consumer may want to perform similar checks in
addition to checking where a provider is hosting their service from in order to
ensure a reliability of service.
Other sources of information
WSDL/SOAP:
Web Services search engine
http://www.salcentral.com
Microsoft .NET:
http://www.microsoft.com/net/
Oracle Technology Network:
new to Web Services
http://otn.oracle.com/tech/webservices/learner.html
SearchWebServices.com:
Web services information resource
http://searchwebservices.techtarget.com/
XML Web Services Directory
http://www.webservicelist.com/
© Becta 2004
Valid at September 2004
Review at December 2004 – Archived in April 2006
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