Page 206 - DCAP312_WEB_TECHNOLOGIES_II

Web Technologies-II

Notes cel=trim(replace(Celsius, “,”, “.”))
if cel= ““ or IsNumeric(cel)=false then return “Error “
return ((((cel) * 9) / 5) + 32)
End function
End class
This document is saved as an .asmx file. This is the ASP.NET file extension for XML Web Services.
The term web service can mean a number of different things:

1. In the broadest sense a web service is any service available via the web.
2. More commonly a web service is any service which is based on web technologies, which
is intended for use by computer programs rather than people.
3. In some cases web service is specifically used to refer to services which use specific web
services technologies (e.g. SOAP or REST).

Throughout this guide the term Web Service will be used to refer to services intended for use
by programs.

While many bioinformatics resources are available on the web, they are usually only available via
web interfaces which are targeted directly at users. This limits their utility in applications which
require systematic access to a resource, where the local resources are not available to install and
maintain the data and software required. Or in cases where a data resource or analytical tool
needs to be integrated into a web portal or workbench application. In these cases Web Services
offer a method for accessing the resource remotely. This has the advantage of delegating the
maintenance costs for the resource to the service provider, rather than having to absorb these
costs locally, and significantly reduces the development and deployment costs for applications
which need to consume data or results from the resource.

Client/Server Model
Web Services use the traditional client server model: a, possibly remote, server provides resources
which are requested and consumed by a client whom the user interacts with. A simple example
of this is browsing the web where the web browser is a client which displays pages and allows
the user to intact with the pages, and the web server(s) provide the data for the pages (HTML,
images, etc.) when it is requested by the client.

Synchronous and Asynchronous Access
While many resources will return a result almost immediately and thus are suitable for
synchronous requests, where the client makes the request and waits for the server to send the
response containing the result, some types of analysis take longer. In these cases a synchronous
request will have issues with timeouts and may make the client unresponsive. To address
these issues services which provide access to such resources provide a mechanism for making
asynchronous requests. This usually takes the form of a collection of methods which allow the
client to:

1. Submit a job and get a job identifier.
2. Get the status of a job. Typically return a status code indicating if the job is pending,
running, finished or gave an error.
3. Get the results of a finished job.

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