Last month we discussed the general architecture of most e-commerce systems and examined the crucial issues of security, extending enterprise capabilities to the Web and the fundamentals of transactional processing (TP). Now let's take a closer look at two other major categories of TP management: the Microsoft environment and managing e-commerce in an object broker environment.
Microsoft Corporation introduced its on-line transaction product as part of its comprehensive Windows NT environment. Microsoft Transaction Server (MTS) manages the COM objects that contain business logic necessary to support your e-commerce system. These objects are typically custom developed and, perhaps, provide an accessible wrapper to your legacy systems. Microsoft utilizes active server pages (identified by their .asp extensions) as a superset of HTML, to provide an easy way to develop Web applications that gain access to these COM objects. The COM objects can provide both transactional and non-transactional access to the RDBMSs that are supporting your environment. MTS does support the two-phase commit process that is vital to distributed transactions, but only when all the business logic runs in the Microsoft COM environment. Because MTS is managing COM objects, business logic running on a UNIX machine updating an Oracle or Sybase database cannot be included in an MTS managed two-phase commit process. This limitation could go away as COM is ported to the UNIX environment.
When the Microsoft Web Server receives a request for an active server page, it resolves all the references to COM objects managed by MTS and converts all the commands on the active server page to HTTP so any browser accessing the page is capable of displaying the output. While MTS offers all the fundamental OLTP elements, it does not at this time deliver the flexibility or capabilities available from traditional TP monitors (Tuxedo or Encina). Because MTS does not provide "location transparency," the developers must know which machine each object is on a weakness that can be challenging if your e-commerce system, like most, is rapidly evolving. If you run a Windows-only shop, MTS is a good way to erect a very basic e-commerce system quickly and easily, and MTS is currently bundled as a freebie with Microsoft NT. But if you operate a heterogeneous multi-platform operation or if your Web-based business demands a fully robust and scalable OLTP solution, Microsoft's current release comes with some substantial limitations.
Most observers view object request brokers (ORBs) as the wave of the computing future, and ORBs are rapidly evolving to fill the growing on-line transactional niche.
Depending on the application and the sophistication of the server, object brokers use Java applets or servlets to launch transactions from the browser to the enterprise. Applets are comparatively smaller Java applications that are downloaded to and reside at the client and are executed in the browser's Java Virtual Machine. In an on-line transaction, a Java applet establishes a connection through the server to the ORB and requests one or more objects, such as a specific inventory or customer-related database activity. Depending on the ORB vendor, IIOP (Internet interoperability protocol) is used to connect Web-located clients to enterprise objects and to support seamless communication between multiple ORBs.
Servlets may be somewhat larger or more computing-intense Java applications that reside, as the name implies, at the server level. Servlets are themselves activated by browser applets and can, in turn, act as clients requesting objects served up by the ORB.
ORB-driven e-commerce systems offer their own unique set of benefits and challenges. ORBs take full advantage of the flexibility and resource efficiencies made possible by the Java approach but are similarly constrained by the limited penetration and version creep of the Java programming language. ORBs, via the object transaction service (OTS), provide reliable two-phase commit performance and the site autonomy needed to support the smooth and rapid evolution of a Web-based e-commerce system. Objects can be written in C, C++ and Java, giving developers the option of wrapping and leveraging existing mainframe code.
ORB vendors are currently working to overcome several architectural and functional challenges. Direct client-to-object links create obvious security concerns, and most vendors now deploy various firewall and gateway products that let clients tunnel safely straight to the ORB. Many ORBs now use multithreading, connection pooling or multiplexing strategies to handle single-client to multiple-object scalability. And, of course, because ORBs were not originally designed to handle the millions of hits typical to a high-volume e-commerce system, developers are working to refine and improve ORB resource management.
The management of transactional processing is one of the keys to a successful on-line business strategy. By understanding the basics of how Web-driven transactions work, organizations can build more productive and profitable e-commerce systems.
J.D. Hicks co-founded Virtual Solutions, a Metamor Worldwide, Inc. company, in 1993. As chief technology officer for Virtual Solutions, Hicks is responsible for directing the research and development of the company's concepts, specifications and applications. For more than a decade, he has been involved in the design, development and support of UNIX database systems. He is knowledgeable about leading data- structures, database design methodologies and the practical use of popular file handlers.
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