Introduction to Web Services
Guido L. Geerts, Robert L. Paretta, and Clinton E. White,
service is a software application on a network that has
an interface through which other programs can gain access.
Web services can be as simple as a mortgage calculator or
as complex as software applications made up of component
modules located all over the world. They are currently being
used to help large and small entities get the most from
their IT resources by allowing the integration of diverse
software applications, from desktop programs to large enterprise-wide
systems. Not only is this useful for day-to-day operations,
it is especially helpful in integrating systems after a
merger or acquisition.
and Accounting Web Services
and accounting-oriented web services are proliferating rapidly.
A particularly interesting one can be found at: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnxpwst/html/odc_ofwstrex.asp.
This web service uses the delayed stock quote web service
provided by Xmethods (www.xmethods.net) to download specific
stock quotes directly into a Microsoft Excel spreadsheet.
Finance and accounting professionals often need data about
a company’s financial performance to use for further
analysis. The normal process is to get the required data
either online or from a printed document, manually enter
it into the appropriate cells of a spreadsheet, and run
the analysis. This web service, however, uses an Excel spreadsheet
to “talk” to a database of stock quotes on the
Internet, downloading specific data as requested.
finance and accounting web service is a subscription service
that provides real-time access to the Edgar database of
SEC filings. Created by XigniteEdgar (www.xignite.com),
this web service enables users to monitor the SEC Edgar
database for submissions and then download recent filings.
another is a web service provided by Inkostar, which translates
accounting data in XML (Extensible Markup Language) format
to IIF (Intuit Interchange Format) for input to a QuickBooks
of Web Services
services do not require extensive modification of existing
software. Dun & Bradstreet offers “Tracking Folders,”
a web service that allows subscribers to continually monitor
customer, suppliers, competitors, or business partners,
for credit checks, collection processes, and more. Subscribers
to the Dun & Bradstreet tracking web service maintain
folders on their local computer and automatically receive
information that could affect business decisions. Essentially,
the service plugs various Dun & Bradstreet software
applications into software applications on a subscriber’s
computer. The subscriber pays an ongoing fee for the service,
and can add additional applications or drop them at any
time without modifying or disabling software applications.
Do Web Services Work?
key to making web services work is data, process, and communication
standards. The communication protocol standard is the same
as the Internet, TCP/IP. All computers can “talk”
TCP/IP. The data standard is XML, a set of syntax rules
for adding meaning to data and for building other XML standards.
The process standards are actually a set of evolving XML
standards: SOAP (Simple Object Access Protocol), for packaging
messages from one software application to another; WSDL
(Web Services Description Language), for describing the
web services processes in terms a software application can
understand; and UDDI (Universal Description, Discovery and
Integration), for describing how to find and use an available
actual workings of web services can be described from a
provider’s and a user’s perspective. From a
provider’s perspective, a web service is created by
using the data, process, and communication standards identified
above to create a web interface to one or more software
applications. Most of the web services described above provide
data from a database in response to specific request parameters.
In essence, a web service responds to a “get data”
command by reading the data from a database and sending
it back to a software application on the Internet. To actually
create such a web service, the provider uses WSDL to define
the allowable read access “get data” commands
that the database management software can understand. The
web service also knows how to put the results in a SOAP
envelope addressed to the requesting software application
and how to send it via the Internet.
a user’s perspective, a software application must
be able to issue the appropriate commands, put them in a
SOAP envelope, and send them to the web service interface
for processing. This usually requires downloading the WSDL
and plugging it into a software application. For example,
to use the Xmethods delayed stock quote web service, users
employ a web browser to access the WSDL, plug it into an
Excel spreadsheet, click the “insert stock quotes”
icon that gets added to the Excel tool bar, and fill in
the necessary information in the po-pup window. Because
the Excel spreadsheet knows how to process XML, it packages
the commands in a SOAP envelope addressed to the web service
and sends it. When the return SOAP envelope arrives from
the web service, Excel knows how to process it and insert
the requested data in the appropriate cells. All current
software packages, including Microsoft Office, Internet
Explorer, and Quicken, can understand and process XML and
can therefore interface with web services. General ledger
and other accounting packages should soon become XML-enabled.
objective is to fully automate the process of finding and
using web services. Web service providers will publish the
availability of their applications, using UDDI to describe
their location and available services and WSDL to define
how to use them. When a user logs on to the Internet and
launches a software application, it will be able to identify
available web services by reading the UDDI. The software
application will then “learn” how to use the
web services by accessing their WSDL definitions. When the
desired web service is found, the user will simply tell
the software application to access it by downloading its
WSDL interface instructions. All of the complexity is hidden
behind the interface.
IBM, Microsoft, and a few others have established UDDI repositories
of web services that work similarly to the stock quote example
above. The future holds fully automated web services from
many entities, available by way of UDDI repositories.
L. Geerts, PhD, Robert L. Paretta, PhD, CPA, and
Clinton E. White, Jr., DBA, are all professors
of accounting at the University of Delaware.