[xliff] Extensibility methods

["Estreen, Fredrik" <Fredrik.Estreen@lionbridge.com>]

Hi All,

I would like to follow up on yesterday's discussion on the <metaHolder> and namespaces to facilitate extensibility. 

The first thing is a point which I don't think has been discussed before, and that is how easy it would be for a tool to make meaningful use of unknown extension data. At first it might sound like a nonworking or bad idea but I think there are cases where it would add value. In many cases metadata could be made useful even if the tools do not know the exact meaning of it, the problem is finding a good way to present it to the user. Here I believe that <metaHolder> as a grouped key/value store is much simpler to work with than arbitrary XML in a namespace. I also think it would make it simpler to extract the metadata for storage/retrieval in a database.

Specific things that I can see a use for is filtering the document on translation units with a specific key/value pair, or providing URL links to other information (or applications). Generically it would be possible to display (and possibly modify) the unknown data as a grouped property grid allowing the user to interpret the meaning of the data. Creating a query builder interface for a database would also be straight forward. To make the filtering / querying as useful as possible I would recommend to also provide a "datatype" for the "value" so that range queries can be used and appropriate input controls created. I think it makes sense to keep the list short and also allow "unknown" as the default type. So unknown, string, number, url and date feels like a good set to me, but I'm sure there are a few more that other would like to see. Another option if we do not want to specify the list we could use some other standard list like the XML primitive types http://www.w3.org/TR/xmlschema-2/#built-in-primitive-datatypes and use anySimpleType as the default / unknown.

All of this is possible with XML namespace extensions, but in my opinion it is much more difficult to create user friendly access to the data. A simple but not so user friendly way here is of course to just use XPATH for search and filtering and somehow display the XML fragments to the user.

Second thing is that I like the process/votes suggested David Filip and think we should start down this path to resolve the issue. First one where we simply vote if we want extensibility at all: 
 * 'Yes' for extensibility by some means
 * 'No' for no extensibility at all
 * 'Abstain' for need of more discussion
            
Second one where we vote on how, using 'Elements', 'Namespaces', 'Elements and Namespaces', 'Abstain' to select how to implement the extensibility, if the 'Yes' votes won the first vote:
 * 'Elements' for extensibility by elements and attributes defined in the XLIFF specification. An example of this method is the proposed <metaHolder> feature.
 * 'Namespaces' for extensibility by allowing third party namespaces at defined locations in the XLIFF documents. As we do in XLIFF 1.2 possibly with additional requirements for conformance and processing expectations.
 * 'Elements and Namespaces' to use both of the above methods to facilitate extensibility.
 * 'Abstain' for need of more discussion

If we choose to allow extensibility and the preferred way(s) to do it we can start looking at the implementation details.

Regards,
Fredrik Estreen