Skip to main content

Representing sub-system dependencies

When we start designing a big system we might also think on how to split our solution in sub-systems. We can end-up having a lot of sub-systems with different dependencies.  The same thing will happen if we start splitting a sub-system in components, we will have a lot of components with different dependencies.
How we can represent these dependencies in a simple and clean way?
I saw different solutions where you can end up with complicated schemas or with trees. Both solutions are complicated to read and people with spend some time understand these dependencies. X depends on Y and Z and so on.
This month I read “Software Architecture in Practice” written by L. Bass, P. Clements and R. Kazman.
I discovered a great and simple way to represent all these dependencies. Dependencies can be represented in a simple table where we will have on diagonal our sub-systems, or different components.
Each input resource that is needed by a sub-system will be on columns. Each resource will be placed in the cell of the row that offers these resources. In the same row, around our sub-system we will be able to see the output of our sub-system and what are sub-systems that depend on our sub-system.
In the following example we have 3 sub-systems. Aircraft System Group (ASG), Avionics Group (AG) and Environment Group (EG). We can observe very easily that the EG depends only on the AG and he need the Ownship and Emissions from it. Also the output of this sub-system is used only by the AG that use the Environment and Emitter Data input.
This example is taken from the book.
As we can observed it is very easily to understand how each sub-system and component interact. Based on this table we can see what sub-systems have a lot of dependencies. Also when we want to change a sub-system we can easily identify the sub-systems that may be affected of this change.
I encourage you to try this approach. If you have time, I really recommend to read the book.


  1. Do they explain in the book why a UML package/subsystem diagram is not appropriate in this case?

  2. The link to the book is http://kind.regards :)


Post a Comment

Popular posts from this blog

How to check in AngularJS if a service was register or not

There are cases when you need to check in a service or a controller was register in AngularJS.
For example a valid use case is when you have the same implementation running on multiple application. In this case, you may want to intercept the HTTP provider and add a custom step there. This step don’t needs to run on all the application, only in the one where the service exist and register.
A solution for this case would be to have a flag in the configuration that specify this. In the core you would have an IF that would check the value of this flag.
Another solution is to check if a specific service was register in AngularJS or not. If the service was register that you would execute your own logic.
To check if a service was register or not in AngularJS container you need to call the ‘has’ method of ‘inhector’. It will return TRUE if the service was register.
if ($injector.has('httpInterceptorService')) { $httpProvider.interceptors.push('httpInterceptorService&#…

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

Entity Framework (EF) TransactionScope vs Database.BeginTransaction

In today blog post we will talk a little about a new feature that is available on EF6+ related to Transactions.
Until now, when we had to use transaction we used ‘TransactionScope’. It works great and I would say that is something that is now in our blood.
using (var scope = new TransactionScope(TransactionScopeOption.Required)) { using (SqlConnection conn = new SqlConnection("...")) { conn.Open(); SqlCommand sqlCommand = new SqlCommand(); sqlCommand.Connection = conn; sqlCommand.CommandText = ... sqlCommand.ExecuteNonQuery(); ... } scope.Complete(); } Starting with EF6.0 we have a new way to work with transactions. The new approach is based on Database.BeginTransaction(), Database.Rollback(), Database.Commit(). Yes, no more TransactionScope.
In the followi…