[Erp5-dev] new business template model

[Yoshinori Okuji]

Hello,

Thanks to Aurélien's work, we now have a fine-grained control over business 
templates. I'd like to describe new features and a proposal for the future 
maintenance of business templates.

Until now, Business Templates are maintained in the form of an XML file, which 
is merely an exported form of a Zope object. This form is monolithic, that 
is, all objects are packed into one XML file, and this was very inconvenient 
when we wanted to examine a difference between two business templates or even 
merge two versions of a business template. In the CVS repository, each 
business template has one file entry.

The idea behind Aurélien's work is to split the exported representation into 
multiple parts in a per-object basis. This way, we can compare, for example, 
only one object between two versions easily. Since the XML file corresponding 
to one object is very small, it is feasible for human to look at a diff (at 
least, when you know how an object looks like).

This new approach has pros and cons. Having multiple files is convenient for 
the development, but not convenient for file transfers (such as download, 
send by e-mail). So the Template Tool supports two different forms of 
business templates: plain format and archived format.

The plain format is a directory and its subdirectories and files. For example, 
the template "erp5_core" has a top directory "erp5_core", and has more 
directories and files under the top directory.

The archived format is just an archived form of the plain format. Currently 
only tar+gzip is supported, but it is not difficult to support more, if 
required. In this format, all files are compacted into one file, so it is 
easy to distribute business templates in this format. However, this format is 
not for human at all, because it is a binary format.

Now, about the maintenance of business templates. To utilize the advantage of 
the new form, we should turn the business templates in the CVS to the plain 
format gradually. Once this is finished, we won't have to share the same 
server for development any longer, because it is so easy to merge changes.

When you commit business templates in this form, what you must take care of is 
to check differences between the repository and your local one before 
committing (i.e. cvs update, cvs diff, then cvs commit). Even with this 
format, if you skip the checking, you would easily overwrite others' changes 
mistakenly. Not all human mistakes can be covered by computers.

YO
-- 
Yoshinori Okuji, Nexedi Research Director
Nexedi: Consulting and Development of Free / Open Source Software
http://www.nexedi.com
ERP5: Free / Open Source ERP Software for small and medium companies
http://www.erp5.org
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