Re: [bdbxml] xmldb like collections?

George Feinberg wrote:
> 
> It'd be N index lookups vs 1, where N is the number of containers.
> However, index lookups are quite fast.
> The trickier part is rewriting a query to reference the containers  
> themselves.

Understandable.

> There is no "query all known/open containers" concept.  That would have
> to be built into the implementation of the XML:DB API.
> You could either rewrite the query to include hard-coded paths, or
> write it to use a variable for the collection/container name, and
> put a loop into the query.

Either way it sounds like a fairly complex customization. Currently we 
are evaluating xmldb's for their capability before selecting one, this 
is something I would add to my list of trade offs from the other xmldb's 
we've been looking at.

Currently, express this trade off list as

1.) useful standard API's.

eXist and Xindice:
xmldb, webdav, xml-rpc, REST

bdbxml:
xml-rpc, bdbxml api

2.) database performance:

eXist and Xindice:
poor scalability in terms of document size.

bdbxml:
better scalability in terms of document size.

3.) Contextual XQuerying and Collection Hierarchy.

eXist:
good capability within db for collection context based XQuerying.

Xindice:
good capability in contextual querying across collections and multiple 
databases.

bdbxml:
no concept of Collection Hierarchy

> 
> You mentioned in an earlier message this:
> 
>> This is much different than in xmldb, the concept of collection is  
>> within the database instance itself, there is 1 to many  relationship 
>> between the db instance and its collections in xmldb.
>>
>> The challenge I see in equating containers to collections is that  in 
>> xmldb an index spans all collections in a db. In bdbxml, it  doesn't 
>> seem you could have an index that spans containers.
> 

I would add to this that Xindice and eXist handle the implementation of 
xmldb slightly differently. Currently eXist works solely on "1 - many" 
relationship between a Database and its Collections, while Xindice 
actually supports a "Many - Many" relationship where the API can access 
multiple db instances on different url paths while working with many 
collections in each db.

> 
> Can you please provide an API reference for Indexes and their scope,  as 
> well as query scope in the
> XML:DB interface?
> 

In eXist here is a javadoc reference to the xmldb API Database and 
Collections API.

http://exist.sourceforge.net/api/org/xmldb/api/base/Database.html
http://exist.sourceforge.net/api/org/xmldb/api/base/Collection.html

Note: eXist is currently considering working on an new version of the 
xmldb API to accomplish some improvements. Now appears to be the time to 
coordinate with other groups/companies to adapt this API to Real World 
cases.

-Mark


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