TTP protocol. Taking into consideration the portability, the ease of configuration, and the performance, we have chosen Apache Web Server. The version of the Apache Web Server used in this implementation is 2.0.63. Web Service Layer: The Web service layer is responsible for processing the SOAP requests received from the client, executing the required Web service operation, and sending back the response to the client. All the business logic for the Web service operation is implemented at this level. Web Server layer Web Service layer Graphical interface NI-Visa Agilent Visa Figure 12.40 Web server architectural solution. Service Delivery Platforms Because we have an Apache Web Server and we decided to build the software in C ++, the best solution for the Web service layer is Axis C ++. One major advantage of Axis C ++ is the possibility to install it as an Apache Web Server Module. VISA Instrument Access Layer: The instrument access and communication will be made using a VISA implementation library and the VISA Server. There are two major implementations of the VISA standard: NI-VISA the implementation provided by National Instruments Agilent VISA an implementation provided by Agilent For this implementation, we will use the NI-VISA. This implementation is distributed by National Instruments for both Windows and Linux platforms. 12.3.2.1.2 Implementation of the Web Service Next, we will present the operations that are implemented by the VeLab Web service. Each operation will be presented focusing on the response and request messages and implementation details. The VeLab Web service offers the following operations: VeLabService executeCommand getInstrumentList getInstrumentStatus executeCommand: operation to execute a VISA command on a specified resource getInstrumentList: operation to obtain the list of all available VISA resources getInstrumentStatus: operation to query the status of a specified Visa instrument The implementation of the service operations relies on the NI-VISA library that provides functions for 