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The database is the
connective link between pdr and pdx. Normally the
user has no need to bother about it's internal structure. Utilizing pdr
and pdx
he works almost exclusively with so called collections
(series of measurements). This is the concept: A collection
saves all values of a concrete series of measuring, each value together
with a
unique timestamp: [...]
2008-12-17 21:45:00 5.9 2008-12-18 05:00:00 6.1 2008-12-18 12:45:00 5.3 2008-12-18 18:45:00 5.3 2008-12-18 21:45:00 4.7 2008-12-19 05:00:00 5.2 2008-12-19 12:45:00 5.4 2008-12-19 18:45:00 4.7 2008-12-19 21:45:00 5.7 [...] If there are five parameters to get measured there are also five collections needed. The user can with pdr list, create and delete such collections at any time. Every collection has a unique name. This name is a combination from the following characters: A...Z
a...z
_
*
+
!
?
^
°
§
$
/
&
[
]
{
}
=
~
The name is case sensitive. The number of the collections and the length of their names are unlimited. Note:
Because of the use of these names in expressions
what happens quite often the names of
collections should be short. There's no argument against the use of
single characters (especially letters).
Two collections have fix names: * and #. The first one is the so called default collection which is always numeric. The second one is the comment collection which is text. These two collections don't have to be created explicitly, they always do exist. The reason for this is their special (nameless) use in expressions. You should use both these collections for the most important use case. Collections have each a concrete type for all of their data values. This type has to be declared during the creation of a collection. Mixed collections are not thinkable at all. There are three possible types of collections:
|
expression | During data input over e-mail
mailboxes, the command line
or text files pdr
interpretes so called expressions.
Every
text
line
is
an
expression.
An
expression
can
contain
several
values,
so
we
have
to
declare
which
value
should
get
into
which
collection.
For
doing
this
we
use
a
simple
syntax
-
the name of the collection is
used as suffix: [date]
[time]
(value[collection])* [; comment]
This definition means:
Note:
if there are two values for the same collection in the same expression
only the latter will be used, there can be only one value per timestamp
in a collection because the timestamp is the unique key.
Date and time have a concrete, not localized syntax: [CCYY-]MM-DD
and
hh:mm[:ss]
ExamplesGiven that we have the following collections in the database: l, m, n (all numeric) and anyway * and #. The following expressions would be correct:5.2
(implicit use of default
collection)
5.2* (explicit use of default collection) 5.2 8l 7n 1m 75/123 (collection /) "This is a string"z 2009-08-16 12:34 5.3 9n ; this is my comment 23:45 15l ; comment only We see that simple data input is a primary design goal even if these expressions seem to be a bit cryptic on the first view. They (look at the first three lines) can easily be entered also with the limited capabilities of mobile phones. They have to be read again only by a machine. You can also, if there's no other opportunity to transmit, put these data into a text file or write them on a sheet of paper and enter them later. |
rejection |
pdr: it can happen that expressions can't be parsed because
of incorrect spelling or other errors, for example in e-mails this
leads to the problem that such a message will be processed again and
again which leads to the same problem, for this reason such incorrect expressions get into the rejections, a
special table in the database containing rejected data, but they can be
corrected later |
selection | pdx: a variaty of values of a collection useable for further
calculations, the selection
is based upon timewise criteria and can contain gaps |
timespan, time duration |
a time span with any length, the
smallest unit is 1s |
timestamp | a concrete point in history with
the precision of a second, contains always date and time |
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