Skip to main content

Notice: this Wiki will be going read only early in 2024 and edits will no longer be possible. Please see: https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/wikis/Wiki-shutdown-plan for the plan.

Jump to: navigation, search

Difference between revisions of "CDOQuery OCL"

m
Line 28: Line 28:
  
 
The most important part in this query is the fact that we are comparing real objects, as <tt>k.belongsTo</tt> refers to an element of type <tt>Patient</tt>. For OCL CDO to evaluate this query correct, we need to pass the context objects <tt>CDOID</tt> object as otherwise we will receive an error. A direct comparison by simply passing <tt>(Patient)p</tt> as context is hence not possible.
 
The most important part in this query is the fact that we are comparing real objects, as <tt>k.belongsTo</tt> refers to an element of type <tt>Patient</tt>. For OCL CDO to evaluate this query correct, we need to pass the context objects <tt>CDOID</tt> object as otherwise we will receive an error. A direct comparison by simply passing <tt>(Patient)p</tt> as context is hence not possible.
 +
 +
==== Query Examples ====
 +
Find all Instances of Patient <pre>Patient.allInstances()</pre>
 +
 +
Get the number of instances of Patient <pre>Patient.allInstances()->size()</pre>

Revision as of 03:24, 19 April 2012

Based on CDO 4.0-SR2

For some basic references to OCL please find http://atlanmod.emn.fr/atldemo/oclturorial/ or http://cs.ulb.ac.be/public/_media/teaching/infoh302/oclnotes.pdf

Model

We have the following, deliberately trivial, model:

TrivialModel.png

We have the entities Patient and Konsultation (Consultation), which hold some generic attributes resp. features. The enumeration Geschlecht (sex) is self explaining. Each Konsultation belongsTo exactly one Patient, it is however not contained by the patient but exists as independent entity.

Queries

This section documents some queries based on the aforementioned model. It is work in progress.

Finding object references

The following OCL query finds all Konsultation entries in the entire repository, that belong to a certain Patient p, "injected" by the context. The element provided by the context is refered as self within the query.

CDOTransaction cdoTransaction = Activator.openSession("demo")
	.openTransaction();
 
CDOQuery cqo = cdoTransaction.createQuery("ocl",
		"Konsultation.allInstances()->select(k:Konsultation|k.belongsTo=self)",
		((Patient)p).cdoID(), false);
 
List<Konsultation> lre = cqo.getResult(Konsultation.class);

The most important part in this query is the fact that we are comparing real objects, as k.belongsTo refers to an element of type Patient. For OCL CDO to evaluate this query correct, we need to pass the context objects CDOID object as otherwise we will receive an error. A direct comparison by simply passing (Patient)p as context is hence not possible.

Query Examples

Find all Instances of Patient
Patient.allInstances()
Get the number of instances of Patient
Patient.allInstances()->size()

Back to the top