8 22 2005-02-15T08:51:32-05:00 $Date: 2005-09-11 10:27:02 -0400 (Sun, 11 Sep 2005) $ NormanWalsh 2005Norman Walsh If I'm ever going to understand Web Services, I'm going to have to build one. Herewith, a sketch of a service I plan to build. Thomas. H. Huxley If a little knowledge is dangerous, where is the man who has so much as to be out of danger? I don't think it will surprise any of my colleagues if I reveal that I just don't “get” web services. I mean, I think I understand what “web services” means at a conceptual level: We've got this nifty XML thing that allows us to markup our data. We've got this nifty internet thing that let's a whole bunch of computers talk to each other. We think there's money to be made from getting computers to talk to each other in a way that is unambiguous and conforms to business contracts. We'd like to make it easy for programmers to write applications that use web services because that helps drive the whole enterprise (and there's probably money to be made in selling tools to programmers, too). So let's combine them! Let's use XML to send data between computers on the internet (which we'll call the web) so that they can accomplish tasks (which we'll call services). Ok so far? To do this, we'll need REST and SOAP and XML-RPC and WSDL and WS-X, WS-Y, and WS-Z. That looks like a whole lot of acronyms for a concept that seems not too hard to grok. I must be missing something. Like most things, I don't think I'm really going to understand this stuff until I use it, so I'm going to build a web service. I've even figured out what it's going to be.

My web service is going to be called “Where In The World” (WITW) and it's going to expose two methods (addresses? service endpoints?): you'll be able to tell it “where I am” and you'll be able to ask it “where is someone”. I'll open the whole thing up so that anyone who's interested can play with it. The “where I am” service for a given user will accept either a latitude and longitude or the name of a known landmark. (Eventually, there will have to be another method to add landmarks, but let's not worry about that now.) It'll remember where they said they were and when they said they were there. The “where is someone” service will return the last known location of a given user. Optionally, it will provide a list of other users and landmarks that are or were nearby. That seems like a not quite entirely trivial set of services that provides a read-only “get information” service (method? endpoint?) and a writeable “put information” service. My plan is to support a RESTful API, a SOAP XML-RPC-style API, and a SOAP document-style API to the services (if I get ambitious, I may even provide an email API and a Fast Infoset or some other binary API). At least to the extent that I currently understand what those acronyms mean. I expect that I'll need to build at least one WSDL file to describe the services. Whether I'll need any of the other WS-mumble specifications remains to be seen. Web service greasemonkeys, tell me, am I in the right ballpark? Have I outlined reasonable services? Do you think there's enough richness there to learn anything?