# XML Interface for Network Services

XML Interface for Network Services (XINS) is an open-source technology for definition and implementation of internet applications, which enforces a specification-oriented approach.

## Specification-oriented approach

The specification-oriented approach is at the heart of XINS:
* first specifications need to be written;
* then documentation and code is generated from these specifications;
* then both testing and implementation can start.
From specifications, XINS is able to generate:
* HTML documentation
* test forms
* SOAP-compliant WSDL
* a basic Java web application
* unit test code (in Java)
* stubs (in Java)
* client-side code (in Java)

## Components of the XINS technology

Technically, XINS is composed of the following:
* An XML-based specification format for projects, APIs, functions, types and error codes
* A POX-style RPC protocol (called the XINS Standard Calling Convention), compatible with web browsers (HTTP parameters in, XML out).
* A tool for generating human-readable documentation, from the specifications.
* A tool for generating WSDL, from the specifications.
* A Log4J-based technology for logging (called Logdoc), offering a specification format, internationalization of log messages, generation of HTML documentation and generation of code.
* A Java library for calling XINS functions, the XINS/Java Client Framework; in xins-client.jar.
* A server-side container for Java-based XINS API implementations, the XINS/Java Server Framework; in xins-server.jar. This is like a servlet container for XINS APIs.
* A Java library with some common functionality, used by both the XINS/Java Client Framework and the XINS/Java Server Framework: the XINS/Java Common Library, in xins-common.jar.
An introductory tutorial called the XINS Primer takes the reader by the hand with easy-to-follow steps to perform, with screenshots.
Since version 1.3.0, the XINS/Java Server Framework supports not only POX-style calls, but also SOAP and XML-RPC. And it supports conversion using XSLT. As of version 2.0, it also supports JSON and JSON-RPC.
XINS is open-source and is distributed under the liberal BSD license.

## Specifications

All XINS specification files are Plain Old XML. Compared to SOAP/WSDL/UDDI/etc. the format is extremely simple. There are specifications for projects, environment lists, APIs, functions, types and error codes.
Below is an example of a XINS project definition.
Here is an example of a specification of an environment list:
An example of an API specification file:
An example of a function definition:

## RPC protocol

The XINS Standard Calling Convention is a simple HTTP-based RPC protocol. Input consists of HTTP parameters, while output is an XML document. This approach makes it compatible with plain Web browsers.
Example of a request:
Example of a successful response:

## Competition

There are no known products that provide an integrated approach to specification-oriented development, similar to XINS. However, there are several frameworks and libraries that provide functionality similar to individual parts of XINS, including:
* JWSDP: Collection of various XML and SOAP technologies for the Java programming language.
* Apache Axis: Java-based framework for SOAP implementations.
* Codehaus XFire: Idem.
* Hessian Web Service Protocol: Binary alternative to the XINS Standard Calling Convention.