[Lazarus] Web development and XML database (Mattias)

[Juha Manninen]

2011/11/17 Mattias Gaertner <nc-gaertnma at netcologne.de>

> **
>
>   XML was invented to markup texts. Later programmers noticed that it is
> also nice for config files.
>
> A few hundred MB of XML does not sound much compared to some big SQL
> databases. But because it is "not that much" we want to search them in real
> time (multiple queries taking less than half a second). That is not a
> trivial task, not in a XML database, nor in a SQL database.
>
>
>
> Another important point is, that our data is hierarchical, has lots of
> optional elements and attributes, the data model changes often and the data
> is inconsistent. Using a SQL database for that would be stupid.
>
> After a year of programming with hierarchical structures I came to the
> conclusion, that hierarchical databases are greatly underestimated. If your
> SQL tables are not filled dense and/or if you have a lot of parent-child
> relationships you should try them out.
>

In 1990's there was hype about object DBs which would replace relational
DBs. For some reason they disappeared.
Now the existing object DBs are built on top of a relational DB, like the
eMatrix I mentioned.

I understood that XML is only the input data format for your DB. It is
parsed into a memory structure and searches are done there. Then it could
be called in-memory DB as well because the XML format is not the essential
part.

Juha
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