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		Subsystem ESI - EAD System Interface
Context Objectives External Stakeholders Internal Stakeholders Oversight Management Stakeholders´ Management Overview Software Concept Consortium Leader Programme Management Safety/Security Management Surveillance Management Training Management Frequentis NedGraphics ISO AviTech SOLITECH MEKON		The ESI subsystem provides a high-level interface to services of other EAD subsystems for external clients of the EAD system. ESI is mainly a system-to-system interface which enables EAD's integration with existing AIS infrastructures. The main focus of ESI is to ease integration and, therefore, to enable external clients to use as much information inside EAD as possible. Mainly the ESI Client Interface and the ESI Validation Suite are visible to the external client. ESI Client Interface The ESI Client Interface provides transparent access to the EAD subsystems. Communication is based on XML, a language designed to represent information in a way that is easy to interpret by the communication parties. Both synchronous and asynchronous communication is supported: synchronous requests will be used mainly by client processes that make direct queries about information from inside the EAD subsystems and expect immediate responses; asynchronous requests will be used for batch processing (e.g. uploading or downloading bulk data). ESI Validation Suite The ESI Validation Suite is used to validate that implementers of a new EAD system-to-system client are capable of implementing a connection of their systems to EAD, without compromising data quality and integrity. The EAD expects a new ESI Client to take 'an exam'. A new Client system will not be allowed to use the ESI Client Interface until it has passed this exam, which will consist of making an application using a number of typical messages, as specified in the ESI Validation Suite documentation.