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Technical System Landscape 
The principle architecture of a NetWeaver process integration landscape is described in the Master Guide – SAP NetWeaver 2004s and in the Technical Infrastructure Guide – SAP NetWeaver 2004s on SAP Service Marketplace at service.sap.com/instguidesNW2004s.
A PI landscape consists of either a full-fledged PI usage type used for communication between various types of back-end application systems (business systems), or of a light-weight Partner Connectivity Kit (PCK) that serves as an endpoint for B2B communication.
A full-fledged PI landscape comprises the following groups of components:
· Messaging components responsible for message processing and protocol handling. These components include the Integration Server (IS) with the central Integration Engine and the central Adapter Engine (AE), optional non-central Adapter Engines, and optional J2SE-based Adapter Engines.
· Tools for design, configuration, administration, and monitoring purposes (Integration Builder, Exchange Profile, System Landscape Directory, Runtime Workbench) that require user interaction and are not directly involved in messaging.
· Backend systems and business partner systems that act as the sender or receiver of messages.
Concerning security, the following components have to be considered in more detail:
· Integration Server
The Integration Server acts as a hub for a set of senders and receivers of messages. Technically, an Integration Server consists of three engines:
¡ Integration Engine
This engine processes XI messages according to the configuration defined with the Integration Builder.
¡ Central Adapter Engine
This engine connects senders and receivers that do not speak the XI message protocol by handing over messages to the Integration Engine and the other way round. Additional non-central Adapter Engines can be installed on an SAP NetWeaver Application Server Java without Integration Engines.
¡ Business Process Engine
This engine is part of the Integration Server, but it is not relevant for security and therefore not depicted in the figure above.
· Non-central Adapter Engines
Technically, there are two different types of Adapter Engines:
¡ J2EE-based Adapter Engine
This type of Adapter Engine runs on the J2EE Engine. There may be any number of non-central Adapter Engines, each associated with exactly one Integration Server with which the Adapter Engine communicates using the XI protocol.
¡ Plain J2SE Adapter Engine
This type of Adapter Engine was already available with XI 2.0. It merely requires a Java Virtual Machine to run.
· Integration Builder
Comprises a set of tools for designing, configuring, administrating and monitoring a PI landscape. The major parts are:
¡ Integration Repository
Contains interfaces and mappings available across several landscapes. The Integration Repository runs on the J2EE Engine.
¡ Integration Directory
Contains meta data for a given landscape, such as routing relations, communication channels, and security settings. The Integration Directory runs on the J2EE Engine.
· Runtime Workbench
Provides tools for monitoring a PI landscape.
· Exchange Profile
Contains the most basic technical configuration data of a PI landscape.
· System Landscape Directory
Describes the components that make up the given landscape.
· Sender and receiver business systems
Depending on the message protocol, there are several types of systems:
¡ SAP business systems residing on SAP Web Application Server 6.40 or higher.
These communicate with the Integration Server by using proxies (ABAP or Java).
¡ SAP business systems residing on SAP Web Application Server 6.20.
These incorporate XI 2.0 proxies which enable them to send and receive XML messages in the XI 2.0 message format. The Integration Server maps between XI 2.0 and XI 3.0 message formats.

XI 3.0 is the XI message format valid for both SAP NetWeaver ´04 and SAP NetWeaver 2004s.
¡ SAP business systems residing on SAP Web AS 6.10 or lower
These do not contain proxies, thus have to communicate with the Integration Server by using RFC and IDoc adapters.
¡ Non-SAP business systems
Any systems that exchange XML messages or other protocols by using the Integration Server. They are connected by using adapters.
The PCK is basically a J2EE-based Adapter Engine that is able to run without an Integration Server, Integration Builder or System Landscape Directory. The PCK targets inter-enterprise communication between business partners where one partner does not employ the full PI usage type, but instead uses the smaller-scale PCK.