[Aperture-devel] Re: RDFContainer again...

[Leo S. <sau...@df...>]

Hi Chris,

btw: chris, thx for the tip with the icons, will help us :-)

regarding RDFContaier:
I would suggest we collect the problems and possible solutions on a 
wiki-page, to have a better overview of the older problems.

here is the answer by me:
https://gnowsis.opendfki.de/cgi-bin/trac.cgi/wiki/ApertureRdfContainerProblems

please answer on the wiki page.
cheers
Leo

didn't get all the e-mails from devel, have to check why....

>Some words of warning on the use of RDFContainer, which make me think 
>again of its approach.
>
>When you use a SesameRDFContainer, its Repository typically has its 
>auto-commit mode switched off for performance reasons. However, this 
>breaks the contract of RDFContainer's API. The reason is that statements 
>in the repository are not visible until a commit is performed. So when 
>you do a put() for a certain property and you later do a put() for the 
>same property with a different value, you expect that the latter put() 
>overwrites the former value. However, when the repository hasn't been 
>committed yet, replaceInternal won't see the first value. Likewise, the 
>get methods will not return a value for that property. When you finally 
>commit, you end up with both values being stored, leading to a 
>MultipleValuesException upon retrieval.
>
>My example classes are already crowded with commit's to make sure 
>certain put and get methods work correctly. There is something to say 
>for this as these classes also provide the CrawlerHandler implementation 
>that manage the repository. However, I now had to add Sesame-specific 
>code in WebCrawler as it depends on the overwriting capability of the 
>put method.
>
>This is a problem with the SesameRDFContainer but I can imagine that 
>other implementations working with persistence storage facilities will 
>have similar issues.
>
>Although I still like the simplicity of the RDFContainer API, this is 
>another item on the list of problems I've had with it. Does anyone see a 
>simple solution for this? Other that adding a commit() method to 
>RDFContainer or using the Repository's auto-commit mode (hurts 
>performance badly)?
>
>
>Chris
>