hHow do i recognise a web service ??

Discussion in 'XML' started by Liza, Jul 3, 2003.

  1. Liza

    Liza Guest

    hi guys,

    call me dumb but

    how do i recognise a webservice ?? if i go to a web site and the
    information i put into some fields are sent to a database? is that
    database itself a webservice?

    what are webservices clients.........websites? or other webservices?
    or both?

    can a stand alone application such as microsoft word be a webservice
    client or does a webservice client have to be built specialy as a
    webservise client?

    if i want to build a website that can collect information from
    interested clients and save them to a database..........how will i
    access my databse as the owner of the service, do i need to build a
    special client application that only i would have access to ? how
    would i retrieve the stored information?


    thanks a lot guys
    Liza
    Liza, Jul 3, 2003
    #1
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  2. Liza

    Andy Dingley Guest

    On 3 Jul 2003 13:31:35 -0700, (Liza) wrote:

    >how do i recognise a webservice ??


    It's a service you get at over the web.

    But to be useful, it must also be "a webservice built out of
    commonplace protocols", so that it's easy for other groups to build
    clients for it. It's not essential to be open in all cases, but it is
    for many and it's useful for all of them.

    Web services (broadly) have been around since the early '90s, but
    weren't any use. You took protocols like CORBA, DCOM or RPC and ran
    them over lashed-up session layers built on IP. Every site did it
    their own way, and nothing would inter-communicate.

    The gimmick now is that there are a handful of common protocols (SOAP
    - also .NET, XML-RPC and some older ones based on HTTP). These
    protocols are easily understood by all competent developers, because
    they're a simple addition to a well-known pre-existing protocol, like
    TCP/IP, UDP, HTTP etc.


    If you ask, "What is a web service ?", then it would have to be a
    paper definiton of a protocol for people to write them.


    > if i go to a web site and the
    >information i put into some fields are sent to a database? is that
    >database itself a webservice?


    A database should never be a web service. Build your web service as a
    service that's _application_ oriented, offering some useful service to
    your customers, at a level of description and abstraction that they
    can understand. Sell them "Store your birthday reminders list on our
    site and have your PDA sync automatically", not "create a table in our
    database and query it".

    A web service that exposes the raw database has two faults; it's not
    robust against switching to a new database to run the old service on,
    and it's also not secure again the all-too-common database attacks (go
    to The Register and search for "SQL Injection Attack")


    >can a stand alone application such as microsoft word be a webservice
    >client


    Could be - but Word is a little unusual, because it contains a
    powerful programming language and the ability to conect to ActiveX
    controls. With the XMLHTTP object of the MSXML control (M$oft's XML
    control for everything) then you can write SOAP clients in JScript or
    VBScript..

    This isn't a good approach though - too complex. And when programmers
    have to do complex things, they get it wrong.

    A better approach is to use a SOAP control (I've no idea if such a
    thing exists). This would build the SOAP layer into the control and
    give a higher-level interface (thus simpler to use) to the JScript /
    Word coder.

    In the world of Java middleware (WebSphere, WebLogic etc.) it;s even
    easier. You find a web service that offers an automatic description
    via WSDL, and it build your code for you. Or else you show it the code
    for your service, and it builds the WSDL for you.

    >if i want to build a website that can collect information from
    >interested clients and save them to a database..........how will i
    >access my databse as the owner of the service,


    However you damn well please. This simply doesn't matter - your
    clients will use another route.

    >how would i retrieve the stored information?


    Simplest explanation article I saw on this (on SOAP) was a demo client
    written in IE 5 JScript by Aaron Skonnard a few years back. It was
    absolutely minimal, but it showed what just a DHTML page in a browser
    could achieve or could connect to.
    Andy Dingley, Jul 4, 2003
    #2
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