Why do we need to differentiate the roles played by XI and ALE? We all are aware of what SAP Exchange Infrastructure has to offer in various scenarios involving different stake-holders. But as I was going through some of the forums on SDN there is some confusion with how XI plays a key role in certain business scenarios over ALE. Moreover many a times we face this question from our customers that why there is a need for SAP XI when we have an existing concept for integration known as ALE. Both ALE and XI have almost the similar functionality but they have their own pros and cons depending upon the business scenario where they are used. So I thought of briefing out these differences in this blog. An Overview of Exchange Infrastructure. Let me first give you an overview of what XI is all about. The goal of XI is to provide a single point of integration for all systems, SAP, Non-SAP, inside and outside the corporate boundary. Now what is single point of integration? ….well I will be explaining that with a help of an example below. XI supports B2B (i.e. Business to business), A2A (i.e. application to application) scenarios as well as asynchronous and synchronous messages exchange. B2B scenarios are those scenarios which exist between two different business partners whereas A2A scenarios are those which exist within an enterprise. In a nutshell, XI enables you to connect systems from different vendors (non-SAP and SAP) in different versions and implemented in different programming languages (Java, ABAP, and so on) to each other. Thus XI holds on an open architecture with open standards and can be implemented in a complex system landscape. What is ALE? ALE stands for Application Linking and Enabling. As the name suggests ALE is an interface which is a part of SAP’s Business Framework Architecture (BFA). It enables integration and asynchronous data transfer between two or more SAP systems or SAP and non-SAP systems. IDOCS (intermediate document) are used for data transfer between the systems. Comparison between XI and ALE. The main difference between XI and ALE is that XI is a middleware whereas ALE is an interface. Now although XI and ALE have similar functionality there are few additional benefits XI has to offer. I have already mentioned that XI provides single point of integration for all systems while in case of ALE there is point-to-point integration between each pair of systems. Let me give an example. Suppose there is a complex landscape where there are 10 different systems and we need to integrate these systems. So each system has to be connected to every other system in the landscape. For that purpose we need to do point-to point integration using ALE. This becomes slightly tedious for the consultants and what happens if one of the interfaces fails? SAP XI is the solution .Our job becomes much easier by using XI as a middleware. XI brings with itself something called as centralized integration platform. In other words it avoids hard coded settings. In case of ALE both sender and the receiver should be able to identify each other in order to integrate. But using XI sender and the receiver need not identify each other as it becomes XI’s role to do that and whatever changes are to be done, it can be done in XI and both sender and the receiver need not be disturbed. That means there are separate mappings for each sender-receiver pair but all of them are centralized at one place. In this way, XI is more flexible as compared to ALE. Of course in a scenario where only two systems (one of them is SAP) are involved then in that case customers can choose ALE as there is only single point-to-point integration. Another important point is that XI is an EAI (Enterprise Application Integration) tool and it brings the concept of SOA (Service Oriented Architecture) whereas ALE is a part of BFA. XI clearly abstracts the integration logic with application logic. Since integration logic resides in one system it reduces the cost of maintenance. As per my knowledge 60% of the IT services’ cost goes into maintaining the systems. With introduction of XI, companies have observed a drastic reduction in the maintenance cost. Besides all these, there is an added functionality of XI – BPM which stands for Business Process Management. Using BPM one can collect or split messages and receive or send them to multiple systems. For e.g. you need to send material master data to 5 systems you don’t have to create one IDOC per system unlike ALE. All you need to do is to create one single IDOC and send it to XI which in turn will distribute it to 5 different systems across the network. Similarly BPM can be used whenever there is stateful message processing. SAP XI coupled with IDOC has an added advantage. No doubt that despite the new ways of exchanging business data via Web Services (SOAP), XML files, etc. IDOCs (Intermediate Documents) exchange is still the most popular integration technology since we can use them with SAP Exchange Infrastructure. One can expose an IDOC interface via a Web Service or map a JDBC call to an IDOC interface and also one can post the data from the IDOC to a Web Service call. In this way, maintaining and understanding the integration in a complex customer landscape becomes relatively easier using SAP’s Exchange Infrastructure. SummaryWhy XI is better than ALE? 1. XI acts as a middleware and provides single point of integration for all the systems while ALE is an interface which provides point-to-point integration. 2. XI provides pre-defined content unlike ALE. 3. XI has open architecture and uses open standards like XML. 4. It introduces the concept of BPM which enables message splitting in a complex scenario. 5. Reduces the maintenance cost in case of complex business landscapes. Why ALE is better than XI? 1. In a scenario where only two systems are involved one can use ALE. There is no need of XI as the scenario is not complex. Thus it reduces the additional cost of using XI. 2. If one doesn’t have to implement a business logic in the middleware and simply pass an IDOC in that case only ALE can be used you need not couple it with XI. I hope through this blog I am able to do some justice to the topic. In case there are any corrections or comments you are free to post them.