Proposal for a Sitemap <-> Java API contract for Lenya

(originally started by TorstenSchlabach - please add your comments with name)

Background

There is a high level of agreement amoung Lenya comitters that

This relates to these two threads on the dev mailing list:

Note: Sometimes the threads are not properly linked together, so if you want to catch up what was been dicussed, make sure you find all mails on the subject using the subject search of your favorite archive.

The need for contracts

Contracts are good anyway, but they are most needed when it comes to publications. The impact of changes to Lenya on a publication should be kept minimal. In other words, at least the Lenya <-> Publication contract should be as stable as possible and as upwards compatible as possible to make it easy for users to upgrade to a new version of Lenya once it will be released (or even before!) without having to start a migration project on their publication. Requiring adoption of publications to new Lenya releases will hold people back from upgrading and newer is better!

There is certainly a lot of other contracts involved that should be kept stable if at all possible, for example the contract between the Lenya core and plugins (editor or ressource type). Taking a look at this drawing from one of the emails mentioned above might help to identify other contracts needed. But the purpose of this proposal is to define a contract between the Java and the sitemap layer.

+--------------------------+----------+
|                          | Plugin A | <--> Jackrabbit
|                          +----------+
|                          | Plugin B | <--> SVN
|                          +----------+
|                          | Plugin C | <--> Wiki Resource Type
|                          +----------+
|                          | Plugin E | <--> Link Resource Type
|                          +----------+
|   L e n y a   C o r e    | Plugin F | <--> SVG Editor
|                          +----------+
|                          | Plugin G | <--> RSS Feed Includer
|                          +----------+
|                          | Plugin H | <--> XDoc site.xml editor
|                          +----------+
|                          | Plugin I | <--> CSS Editor
|                          +----------+
|                          | Plugin J | <--> (your wildest phantasies)
|                          +----------+
|                          | Plugin K | <--> OpenOffice Desktop Int.
+-----------------+--------+----------+
| Template A      |        |
+-----------------+        |
| Pub AA | Pub AB | Pub C  |
+--------------------------+

Comment by AndreasHartmann

I see two separate concern areas:

Customization and implementation of CMS functionality

IMO the major concerns in this field are:

  1. hide complexity from the integrator
  2. provide an API which is minimal (reduce the impact of changes) and complete
  3. use Cocoon concepts
  4. provide simple concepts with reduced flexibility
  5. allow complex customization with full flexibility (if appropriate knowledge is possessed)

Approaches:

Presentation of content

Important points:

  1. provide access to all necessary information in sitemaps and XSLTs
  2. define XML-based interfaces for components (e.g., navigation elements)

Approaches:

Proposal: Eliminate all direct file access from Lenya core and publication sitemaps

There should not be any src="xyz" attributes found in any Sitemaps anymore, where xyz means any URIs without a specific protocol mentioned which means the SourceResolver will default to the file resolver and and use the URI provided as a file system location which is interpreted relative to the sitemap location in the directory tree.

This includes not to use any src="context:..." sources as well as they basically do the same.

Current Status

The lenya: protocol is a very good example of determining in the Java layer where to look for the actual input. In other words, the lenya: protocol hides all the complexitiy (which belongs into the Java layer) from the sitemap. The sitemap can just go to Lenya and request the document "abc" by using something like src="lenya:/abc.xml". The Java layer will use it's knowledge about the context to determine the actual location of the document. This proofed to work very well.

Open for discussion

The question will be how this might be extended for locating input other than document / content XML files, such as

It comes down to

ProposalSitemap2JavaApiContract (last edited 2009-09-20 23:27:50 by localhost)