SOA Integration: Functional View
The business community is not concerned with IMS, VSAM, CICS, IMS-TM, 3270, and other legacy technologies. Business users think in terms of the applications they use, the business processes they execute, and the information they need access to. Their view of the world looks like this:
The business community sees the business processes/services as a cloud, something they can see but is far from their world, and not something they can touch or feel. The information they need is like a mysterious 'black box'. It resides somewhere in a dark corner of the IT department.
The business community's functional view of the world consists of four things:
- Applications — This is their interface with the legacy systems. These applications are typically accessed via archaic 3270 (IBM mainframe), 7561 (Fujitisu mainframe), UTS, T27 (Unisys mainframe), and 5250 (IBM iSeries/AS400) 'green screen' terminals. The users don't necessarily like these interfaces, but this is what they deal with today. They would prefer to get access to information like they do at home, through web browsers and cell phones. They wonder why they can do online banking at home from a nice browser interface, but when they go to work they must use a 'green screen' to look up account information for a client.
- Legacy business processes/services they access — Create new account, check account status, check payment information, submit purchase order, and so on. These are some of the business processes and services the user community executes every day. Most of these transactions ultimately take place on a legacy system.
- Legacy information they need — The user does not care where the information resides. It may be in relational databases on mainframes, hierarchical database, network database, flat files, and so forth. They just want access to the data now and in a fashion that is flexible, adaptable, and easy.
- To an IT person, the business community's view of the world is way too abstract. The IT community will look at SOA Integration in a more technical context and include things like transformation services, legacy connectors/adapters, and types of legacy artifacts. The functional view from the technical perspective looks like this:
The view consists of four basic components:
- User Interface —In the legacy world, these are most likely to be CICS transactions that are executed from COBOL applications and rendered on character-based 'green screens'. The most widely used mainframe 'green screen' is a 3270 device that was manufactured by IBM. These devices have long gone the way of the dinosaur. However, there are many software packages that emulate the 3270 device protocol on modern hardware such as the PCs.
In the modern world of IT, the user interface could be a PC-based web browser, Java, or .NET application, a browser enabled PDA or cell phone, or any device that understands HTTP.
- Legacy Service Bus (LSB) — LSBs have existed for decades. Traditionally, they have taken the form of FTP, mainframe CICS to CICS calls, custom COBOL applications, TCP/IP and/or SNA socket communication, messaging queues, and the list goes on. IBM has done an incredible job of getting IBM MQSeries to be the backbone of most legacy service buses. Most mainframe shops use MQSeries to integrate legacy systems with open systems, internal systems, and packaged applications.
The world of IT service bus integration moved to RPC, DCE, Corba and others in the late 1980s. Most of the technology has still not become commonplace with FTP and queuing still ruling the legacy world, even today.
Today,Enterprise Service Bus (ESB) products have become the common means to integrate systems. LSB is a specialized ESB that allows you to expose the mainframe artifacts. The component that makes the LSB a superset of an ESB is the legacy connectivity software.
- Legacy Services Engine (LSE) — Business users don't see this piece of the architecture and really don't care about it. But it is central to the legacy SOA integration architecture. This technology/software stack is where the magic happens. The magic is making legacy hierarchical and network data stores appear as relational data (and mainframe DB2 accessible from open systems), legacy business transactions look like Java or .NET transactions, and legacy interfaces as accessible as just another Web service. The LSE also provides features such as governance and security that the business users are concerned about. There are other features such as scalability and performance that are transparent to the business user, but are expected to be in the platform. Lastly, features like adaptability, flexibility, auditing, and management are not the domains of business users, but are an IT management concern. Adaptability and flexibility could be argued as transparent business user features, but we put them in IT domain features because business users don't care how rigid or nonrigid that infrastructure is, they just want what they want right away.
- Legacy Artifacts —These are the data, application processes, and the user interface. Application processes could be actual COBOL modules, transactions, stored procedures, or even dynamic SQL. To the user, they just want to see the information that is important to them. To you as the IT person, the decision, which legacy artifacts to base your Legacy SOA Integration platform on, is a very crucial one. In most cases, a hybrid, or a combination of the above is what your architecture will require. Typically, IT will not have a comprehensive or corporate SOA plan, let alone a plan for their LSB. So they will take the 'easy path' and expose legacy 'green screens' as Web services. As we will learn later in this chapter, this may not be the best approach.
Note
Keeping It Real: It is possible to call legacy services directly from a script, Java application, or an HTML page. However, your overall SOA architecture becomes even more chaotic than your legacy 'Accidental Architecture' was earlier. A complete Legacy SOA Integration platform provides services such as orchestration, messaging, presentation and data access services, service management, central control, transformation, security, and monitoring in one easy to use solution stack.