Web Services

Future applications will be executed by cooperating Web Services.

Applications will NOT be Executables

Future applications will not contain large masses of compiled executable code. Applications will be broken down into a number of smaller individual services that are easier to create and easier to maintain. Individual services will be developed and maintained by smaller groups of people.

Applications will be Services

Services are not the same as executables, or COM-objects, or DLL-files. Services will most often return HTML and/or XML pages as answers to submitted requests.

Services will be developed using the following rules:

• Services will be defined in XML
• Services will not be purpose built
• Services will not contain compiled code
• Services will scale and relocate
• Services will be easy to create and edit
• Services will be self describing
• Services will support other services

Services will be Defined in XML

We believe that services will be described in an Application Markup Language, and that these descriptions will be stored in a database or in XML files.

We also believe that standard service engines will provide application services by interpreting these XML descriptions.

Services will NOT be Purpose Built

Our computers are full of applications that were purpose built. These applications will quickly die, because they cannot manage changes in their requirements.

Creating purpose built applications is a terrible waste of money and time. We (and the people that pay for our applications) want flexible and generalized applications that can gracefully support future changes, without a high additional cost.

Our future applications will have to be created from a set of flexible standard services that can serve a lot of different requests. Future, not even thought about, changes should easily hook into our application without crumbling or destroying it. 

Services will be aware of future changes and gracefully adjust to changes in either the amount of services or in the exchange format. The application and the data exchange format must support both extensions, removed elements and version controls.

Services will NOT contain Compiled Code

Services will not be coded if it can be avoided. If a service has to be coded, a scripting language will be used. Services should not be compiled into executables. That makes services too hard to access and too hard to edit.

Pre-compiled components used in an application will threaten the possibility of creating an application that can move, scale and gracefully support future extensions or changes.

Services will Scale and Relocate

Services must be able to scale from supporting a few to many thousand requests per day. Services must also be able to spread from one server to many, or to move from one server to another without breaking the application. Services will be independent of physical server, and be located by standard Internet Uniform Resource Locators (URL).

Services will be easy to Create and Edit

Since services are described in XML, a standard XML editor can be used to create and edit services. Future services will be created and modified by editing their properties and methods, not by changing executable code.

Services will be Self Describing

Application clients will be able to query a server for a service and to ask for the current server functions.

Clients and servers will also be able to exchange data in a way so that both understand each element in the data.

Applications will use an XML based information vocabulary with a self-describing DTD (Document Type Definition) or Schema, to exchange information and data.

Services will Support other Services

Applications should be able to cooperate with other applications. Future services should be created with the same rules, and be able to connect to each other with standard Internet links.

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