| Description | In some domains systems may require a global ordering of interactions. In other domains distributed systems are not requiring that events not dependent on each other happen in a strict order, and often this simply cannot be even assured. Telecom systems are typically such. For example, when X number of SIP users, each represented by a component shall register to _different registrars_ (so not to the same one), the order of registration depends on the order of starting the components in a real implementation of the test, the delay between the client and the registrar, etc.
Current version of TDL supports only a user friendly description of tests for systems requiring strict ordering.
In principle the parallel combined block could be used to specify behavior without the need of global ordering, but it suffers from several problems:
- users in these domains are not used to explicitly identify independent ordering of independent events (i.e. when using MSC or UML SD), it may easily be forgotten;
- as it should be used in each case of independent orders, it complicates the test descriptions;
- when there are more than just a few independent interactions, it makes the description long, inconvenient to create and hard to read;
It is proposed to allow test descriptions without global ordering in the language and add a global (i.e. at the level of TD) attribute identifying that a given description doesn't use global ordering. |