CASoft Blog     CASoft Blog

         Communication Aspects in Software Engineering

12 September 2009

The under-estimated benefits of components

Filed under: UML — Tags: , , , — admin @ 18:02

Components Based Architecture has been formalised and publicised by UML-RUP more than 10 years ago, and the benefits of this approach are still unknown or under-estimated by most.

It escapes me how, in the 21st century, enterprises can ignore the return on investment (ROI) that can be achieved with components.

The most commonly missing piece in the software engineering puzzle today is the architecture document. I keep seeing projects after projects documenting detailed designs after gathering the requirements and no architecture.

When no components based architecture exists, Managers are reduced to finding and selecting solutions at project level.
With well documented components, encapsulating meaningful functionality, it is for example possible to:

  • Find Commercial-Of-The-Shelf (COSTS) solutions for one or several components.
  • Outsource the development of low added-value components.
  • Reuse components from other applications within the company.

Components are however a science and there is more to it than what meets the eye…
See previous article RUP – Component Based Architecture

11 May 2009

RUP – Software Component Architecture

Filed under: RUP,UML — Tags: , , , — admin @ 09:11

What is Architecture?

  • In computer science, Architecture is the nature and structure of a system that determines the way it operates.

What Architecture is not:

  • Architecture is not a Framework: While an architecture can take into account the use of a framework, the definition of a framework is not sufficient! A framework is just one component.

The Technical Architecture (or Model of Architecture) is the nature of the system. For instance, it could be:

  • Monolitic
  • Client Server
  • Distributed
  • N-tier

Paradigms can be integrated, such as:

  • Model-View-Controller
  • Software Components
  • Design patterns

A framework can be defined, as part of the technical architecture.

The business architecture defines the structure of the system.
It should outline the different parts of the system, their role and their relationships, as for instance:

What Does Component Architecture Mean for RUP?

  • Components are cohesive groups of code, in source or executable form, with well-defined interfaces and behaviours that provide strong encapsulation of their contents, and are therefore replaceable.
  • Architectures based around components tend to reduce the effective size and complexity of the solution, and so are more robust and resilient.
  • In the examples below, there is the same number of objects, but a different level of complexity:

Definition for Software Component

  • A Software Component is an independent portion of code that is accessed through a defined interface.
  • Software Components may be just imaginary, and can always be defined whatever the technology used!
  • Software Components may also be physical entities, such as a library (e.g. DLL) or a distributed component (e.g. EJB, CORBA, DCOM, Web Services, etc.)… but not necessarily… and it is not because EJB are used that it is a well-thought Software Component Architecture.
  • Physical Software Components may be reused, purchased and/or replaced.

Business components are those that implement the functionality specific to a business.
A “Computation Engine”, which provides specific computation services, is an example of a business component.
Business components are more difficult to reuse than technical components, due to their specific nature.

Technical components are those that implement generic functionality.
An example of a technical component is “Document Printing”.
Technical components can be designed in order to be reused. They can be part of a technical framework.

Why using Software Components?

  • They usually manage to reduce the complexity of a software, by identifying well defined interfaces and independent portions of code.
  • While it is rather inefficient to give Use Cases to develop to Programmers directly, it is much more effective to give components to implement. ==> Would you envisage to outsource the development of a use case? It is easy to outsource the development of a component, or to buy an existing one.
  • This approach eases and improves workload estimations, planning & task assignment.
  • To reuse components is an efficient way because they are already developed and tested.

Components can be developed in order to be reusable, especially the components that provide common solutions to a wide range of common problems.
These reusable components, which may be larger than just collections of utilities or class libraries, form the basis of reuse within an organization, increasing overall software productivity and quality.
Before promoting furious reusability however, ensure that great experience and knowledge has been acquired in the domain of software components.

Because they are well defined, Components can be refactored with less pain than in a not-so-well structured / organised Architecture.
The interface of the component may be mostly unchanged, while the implementation is entirely reviewed.
Even if the interface is changed, finding the impacted code will be easier than finding what is using the multiple classes and methods that compose the component.

In the beginning of Software Development, documentation and system integration were usually poorly undertook, the Architect was often asked to contribute to the development effort, and the Customer would get to perform most of the testing.

RUP recommends to implement “Use Case Packages” as components for requirements, in order to gather requirements by type of functionality.
Indeed this approach will ease the following analysis and design of the application with software components.

Identifying components may be performed this way:

  • Identify different modules, packages, subsystems and layers, e.g. Billing and Subscription modules.
  • Try to find common features, e.g. printing out.
  • Split modules, define interfaces and relationships with other modules.
  • Iterate and go deeper to find as many components as possible. Use top-down approach, from Graphical Interface towards Data, and bottom-up approach at the same time.
  • Then apply patterns such as Model-View-Controller.

The Components specification will provide a brief description of the components and their relationships.
The result is usually described with Composite Structure or Component Diagrams and accompanying text, providing a high-level description for each component.

The Components Analysis will provide a brief definition of each component, and a detailed definition of its interfaces and relationships.
At this stage, Components are black boxes.
The result is usually obtained and described with Sequence Diagrams and/or Collaboration Diagrams. Class Diagrams can be used to describe the interfaces.

The Components Design will provide the detailed description of what is inside each component / inside the box.
The result is usually obtained and described with Sequence Diagrams, Collaboration Diagrams, Class Diagrams, State Diagrams, etc.

The implementation of the components can now easily be performed by a Developer or a Team.
The team will be responsible for maintaining the design of the component and for unit testing the component.
The team might be the supplier and/or the customer for another component/team.

Components can be individually tested and gradually integrated to form the whole system.When performing unit tests of a component, moke components (giving fake answers) can be used to form the test-bench of the component to test.

Note also that Service Oriented Architectures (SOA) are necessarily based on Software Components Architectures. Components are then implemented as services (Web-services, CORBA, RMI, etc.), which provide the benefit of being loosely coupled.

23 April 2009

Describe Business Processes with UML

Filed under: UML — Tags: , — admin @ 08:32

When describing requirements using UML, any attempt to order use cases or provide sequence information amongst use cases is bad practice, and can only lead to misuse of the UML use case diagrams.

One need to describe the Business Processes for the system under study, as this will provide the order in which things shall happen in much details.
Business Process can be documented in the Overview/Context section of a Product Requirements document.
OMG defines a BPMN notation to describe Business Processes (see, which is basically based on a UML 2.0 activity diagram with a number of additional icons / features. This notation however doesn’t add much other than confusion for the non-expert. I am indeed very much in favour of self-explanatory / unambiguous diagrams, as in my experience UML diagrams must be reviewed and approved by subject-matter-experts who usually are not UML experts. So, unless you have a very good reason for using BPMN, just use activity diagrams to describe Business Processes.
BPMN, while based on UML 2.0, is still in need for a consolidation with UML notations.

Otherwise, it is important not to undertake UML without a methodology. In order to be highly successful in documenting a system of any complexity, it is important to follow a formal methodology.
I personally like to use a methodology based on RUP, especially for the documentation of the requirements and the architecture, while agile approach principals can be used for the design and the development…

31 March 2009

Unambiguous and understandable UML

Filed under: UML — Tags: , — admin @ 17:59

The original and fundamental phylosophy of UML is to be unambiguous and understable by most, without requiring an in-depth knowledge of a complex semantique.
This phylosophy had for objective to facilitate the communication in between the different stakeholders of Software Engineering projects and to federate the notations to promote common understanding and shared vision.
It is obvious to me that the original phylosophy is getting diluted progressively amongst the different additions that have been made to the standard over the years.

I do find myself very much in tune with this presentation umlbooch.ppt made by Grady Booch, and which promotes the need to address the increasing complexity of the systems to develop.
My personal vision is to try to keep UML unambiguous and understandable by most, in order to get as many people on board as possible and to address the problematic of the increasing complexity.

9 March 2009

Initiation to UML

Filed under: UML — Tags: , — admin @ 16:38

I organise several Initiation to UML courses, which include hands-on exercises, such as:

  • Requirements Analysis using UML
  • Software Architecture Analysis using UML
  • Software Design Analysis using UML

These 3 courses are usually intended for Software Developers, Architects and System Analysts, and form one entity that provides a coherent overview of UML and a methodology based on RUP.

A complete UML course will normally take 5 days, but I like to taylor the presentations and exercises to the client’s needs.

When people start learning UML, they want to know and usually focus on the syntax. I believe the philosophy and approach are far more important, and the syntax can readily be found on the Internet or in books.

Believing in UML and its capacity to improve communication, robutness and predictability in the Software Engineering industry, I am always keen to promote it.

I also provide coaching and mentoring.

I would be delighted to have a brainstorming session or chit-chat with you on the subject any time. Contact me at

8 March 2009

Why UML?

Filed under: UML — Tags: , — admin @ 16:15

The Unified Modelling Language (UML) was published in 1995 as a merge of several older notations and approaches, including in particular OMT (Object Modelling Technique), Booch method and OOSE.

The objective of UML was to put together a common syntax, which would be simple enough to be readable by about anybody, while being unambiguous, along with methodology guidelines (which came in force years later with RUP).

The challenge in Software Engineering today is to describe a sometimes complex system in simple terms, without ambiguity and without omitting major concepts… So that everyone on a project has the same understanding, from the Junior Developer to the Project Manager and the Customer.

Why undertaking UML?
–The UML is an OMG standard,
–The UML has a wide acceptance in industry,
–There are a lot of tools which support the UML,
–Use of the UML is independent of software development processes,
–Object-oriented design has become very popular in software development projects,
–There also is a lot of textbooks about UML.

I give UML courses. Contact me at

Powered by WordPress and