After you run the sample, you can study the source files to learn how the sample
works.
How this sample works
The entities, attributes, and events are defined in the file
trainBOM/bom/train/BusinessModel.bmd. Each shared aggregate is an attribute of
an entity type in the business model definitions and is specified with a data type of
number or
numeric. The shared aggregate definitions are on the
Statements tab. For example, the aggregate named
total amount
reimbursed LY is defined as an attribute of the
train
entity:
a train is a business entity identified by a train id.
a train has a departure station.
a train has a theoric amount reimbursed (numeric).
a train has a total amount reimbursed LY (numeric).
a train has a total amount reimbursed (numeric).
a train has an average delay (numeric).
a train has a 'number of delay more than 3h' (numeric).
a train has an maximum delay LM (numeric).
a train has an maximum delay LMLY (numeric).
The sample demonstrates the following aggregation operators: maximum, minimum, average, total,
and number of. It also shows different ways to define the shared aggregates.
If you always want to query the event-related aggregate over the same time period of a day or a
week, for example, you can limit the events to a specified period or time point by using the
during construct or a
where statement in the shared aggregate
definition. For
example:
the total amount reimbursed LY of a train is aggregated from train delays ,
where this train comes from the train of each train delay
as the total amount reimbursed of all train delays during the calendar year of 1 year before now ,
where each train delay is before 1 year before now
available for 5 years .
If you want to query the event-related aggregate over different time periods, use rules to
specify the time period and the number of events from which to calculate the result. For example,
consider the following aggregate
definition:
the number of delay more than 3h of a train is aggregated from train delays ,
where this train comes from the train of each train delay
as the number of delays of all train delays ,
where the delay of each train delay is more than 180
and it is not true that each train delay is on Saturday
available for 1 years
with a resolution of 1 hours .
In this example, the resolution of the aggregate is set to 1 hour, and the available period is 1
year. A resolution combines the data of multiple events over its specified period. You can specify a
temporal resolution in the aggregation definition to improve the performance of the engine. The
default resolution is 1 second. The available period defines the period during which the aggregate
value can be queried.
You can define the period to be queried in the following
rule:
when a train delay occurs
if
the number of delay more than 3h of 'the train' over the current year equals 5
then
emit a new alert where
the message is "The number of delays that exceed 3 hours this year is 20% higher than the yearly maximum acceptable target. " ;
This is an aggregate definition that doesn't contain a reference to now. When
the aggregate statement contains no conditions, a rule can specify a time period from which to
retrieve a calculation.
