Zope Page Templates
What we have seen so far is very nice for dynamic content generation. But one of the best things about DTML (or any other sophisticated server-side macro language) is the ability to define menus in one document, headers in a second and footers in a third, and then for each page to import them as necessary.
One way to handle this situation is to create three separate templates (menu, header and footer) in the current folder, importing them with TAL expressions such as:
<span tal:replace="container/menu"> menu goes here</span>
TALES looks at the current template's container, retrieves the menu object (which happens to be a page template itself) and inserts its contents into the current document in place of the <span> tag.
Another way to approach DTML's flexibility is with the use of macros. Macros are common in many programming languages and allow us to create functionality that expands at runtime. The ZPT macro language is called METAL, and like TAL and TALES, it is defined and invoked within HTML attributes, placed in the “metal:” XML namespace. METAL macros can define “slots”, or parameters, into which parameter values can be bound. It's easy to imagine how you could create a macro that handles the overall site design, with each document fitting into the slot that this macro provides. Changing the macro definition would effectively change the design of the entire site.
When I first heard about ZPT, I was sure that it was yet another new way to create templates that are incompatible with other techniques and technologies. But over time, I have become convinced that ZPT is indeed a clever and elegant idea, and one that offers advantages to developers and designers alike. Although it is not a complete replacement for DTML, I believe that most of my DTML usage can now be replaced by a combination of TAL, TALES and METAL. I look forward to seeing how these technologies improve over time and how they are integrated more fully into Zope in the coming months and years.
Reuven M. Lerner is a consultant specializing in web/database applications and open-source software. His book, Core Perl, was published in January by Prentice Hall. Reuven lives in Modi'in, Israel, with his wife and daughter.
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.
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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.
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