Linux Network Programming, Part 3
CORBA is an example of what is termed “middleware”--a technology that enables the separation of applications into three distinct sections (see Figure 5):
The presentation, or user interface, tier
The business logic, or control, tier
The data storage tier
The presentation layer could be an HTML form or a Java applet (as in Figure 5). Extracting the control logic from the presentation allows you to network-enable the presentation of your application.
It also allows the end user to use less expensive hardware to interact with the application, since their equipment is now responsible only for rendering the information supplied to it by the control logic. In addition, the presentation system does not need to have any knowledge of where the data originally came from or in what format it is stored in the database—all it needs is the interface to the middle layer.
The control logic can perform access management, alter the view of the information as required to enable different users to view different subsets of the same data—perhaps for security reasons. For example, a doctor in a hospital may want to see the patient's medical history, whereas someone from the finance department should only be able to see billing information. In Figure 5, either Java or CORBA performs the role of the business logic.
By separating the control logic from the data store, you gain the benefits of distributed computing. Your logic can encapsulate database access, providing you with scalability and fault-tolerance for mission-critical data. All sources of corporate information can be integrated via the control logic to achieve what is termed a “data warehouse”--allowing all the information to be accessed via a single interface (depending, of course, on security clearance).
Legacy systems can be encapsulated, thereby protecting your existing investments. By standardizing the interface between the business logic and the data, you can more easily replace or upgrade database systems. The desktop machines (responsible for presentation) do not need to be modified. The task of replacing a database becomes solely concerned with that action—moving data from one database to another, without affecting the other components of the system.
The control logic can also augment the capabilities of the data storage system, performing additional features, such as searching the information for non-obvious trends (a process called “data-mining”).
The separation of application systems into a number of distinct tiers, and standardizing the interfaces between these tiers, ensures that when you make a modification to one layer, the effect of this change on your entire architecture is localized.
In this article, we introduced the Common Object Request Broker Architecture, a developer's tool in implementing applications based on distributed object technology. We also discussed the benefits of an object-oriented approach to network programming over traditional functional approaches, such as the use of RPCs. Finally, we introduced one of the main interests in CORBA technology—enabling the deployment of business applications on a network using a multi-tiered approach.
The next article will discuss the various ORBs available for Linux and how to begin programming with CORBA.
Mark Donnelly is also a postgraduate student in the ECE department at the University of Limerick, Ireland. Mark is interested in Aikido, Linux, CORBA, Distributed Agents and Alpha World. His e-mail address is firstname.lastname@example.org.
Dr. John Nelson is a senior lecturer in Computer Engineering at the University of Limerick, Ireland. His research interests include telecommunications (mobile/broadband), VLSI design, and software engineering. His e-mail address is email@example.com.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide