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Software Factories - Part 1

Embracing product lines, model-driven development, and developer guidance

There is a lot of commotion and hope around Software Factories in the community today, which was originally sparked by the Software Factories book of Jack Greenfield and Keith Short. The promise is that Software Factories will streamline and automate software development to become more efficient and produce higher quality software. However, at the same time there is a lot of confusion about what Software Factories really are and how to implement them.

In the first part of our Software Factory series we start with working out the problems we face in software development today, which are the motivation for Software Factories. We will explain the basic concepts, the theory behind it, as well as the basic building blocks.

Part II will then give an introduction to the actual implementation of Software Factories. For a good part these two articles are based on our findings while writing the book Practical Software Factories in .NET.

Problems in Software Development Today
Today's software development is mostly based on craftsmanship and most software system are unique pieces of "art" that require plenty of manual effort and skills. At the same time, a large part of software projects is not completed on time or within budget, is lacking features, delivers the wrong functionality, or in the worst case, completely fails [3]. Jack Greenfield and Keith Short identify the following factors as the main reasons for the unpredictability we see in today's software development projects:

  • One-off development: Each system is virtually created from scratch. Reuse is very often ad-hock, on very low granularity level (e.g. source code) and not in a systematic and planned way.
  • Monolithic systems and increasing systems complexity: Many systems are very tightly coupled; changes in one part require changes to many other parts because of dependencies. In addition software systems be-come more and more complex.
  • Working at low levels of abstraction: While the size of software systems and their complexity increased dramatically over the last few years, we only saw a comparatively very low increase in productivity e.g. by the move from C to C++, Java or C#.
  • Process immaturity: Either a very formal approach is used, which often lacks the ability to react to changes in requirements in an efficient way, or an agile approach is used which usually does not scale very well.
  • Rapidly growing demand for software systems: Over the last decade we saw a dramatic increase in demand for software. This increase in demand will continue over the next years. With the tools and techniques used today it will be very hard to meet this increasing demand.
The goal of Software Factories is to industrialize software development by exploiting economies of scope that occurs when we build many similar, but yet distinct software systems. Let's now look how Software Factories try to improve these problem areas.

Basic concepts of Software Factories
The Software Factories paradigm is a fairly new concept but it builds on many well known and proven concepts, extends them and bundles them into a coherent paradigm. These four basic concepts are:

  1. Product line development: Product lines allow us to deliver mass-customized software systems where each customer gets a similar but yet individual system [4]. The four main concepts supporting Product Lines are scope, commonality, variability and extensibility. The scope defines and limits the functionality that is provided by a product line. Commonality describes the features that all product line members (applications that are produced using a product line) have in common. Variability refers to the supported differences functionality between the products that we can produce with a product line (product variations). Extensibility allows for additional functionality that gets plugged in or connected in a prescribed way. Figure 1 shows how scope, variability and extensibility relate using a product line approach.
  2. Architectural Frameworks: Provide a baseline architecture that all product line members (products of a product line) have in common. Frameworks also incorporate best practices and patterns for a particular application type, which enables more efficient development with higher quality and a uniform architecture.
  3. Guidance in Context: When applied in the context of a product line, guidance in context helps application developers implementing the variabilities in a particular application. By instructing the developer when to do what and how to do it, many mistakes can potentially be prevented and will eventually lead to more efficient development.
  4. Model-driven development (MDD) and development automation: Allows for modeling software at a much higher abstraction level, using business domain concepts such as workflow, activity or message, rather than developing on a low technical level, e.g. with using terms like class, event, library. Code generators fill the gap between the high-level modeling language and "low-level" code. These specialized modeling languages are also called Domain-Specific Languages (DSL). Software development not only becomes more efficient but it also enables stakeholders without programming experience to participate and contribute to the development cycle.
These concepts build the theoretical foundation of Software Factories. The power of Software Factories comes from combining and interweaving each one of them, as displayed in Figure 2. For example an architecture framework can provide extensibility points required for product line development. Another example would be a DSL that is used to guide the developer through implementing variable aspects of a product line member using domain concepts on a higher level of abstraction than code.

Software Factory Instance
Let's now examine what a Software Factory actually looks like. There are two ways how you can look at a Software Factory:

  • For the software factory author (e.g. a product line architect) a SF is a collection of core assets that make up the com-mon and variable features of a product line and provide extension points to add additional functionality.
  • For the software factory consumer (e.g. an application developer) the Software Factory becomes a part of his development environment that now can be used to develop instances of the software product line more effectively and predictably; as illustrated.
In Figure 3 we can see the Software Factory Schema and the Software Factory Template, which are defined and implemented by the Software Factory authors. The assets in the Software Factory Template are used to customize and extend the development environment of the software factory consumer, or in other words, the application developer. The goal is to enable the developer to rapidly develop family members of the product line as defined by the requirements.

Because we did not want to convolute Figure 3 with too many details it does not show the feedback loop from the Application developer to the Software Factory Architect that exists. Developing a Software Factory, as any other software development, should be done in an iterative way and the described feedback loop is therefore an important part of the development process. Let's now look into these concepts in more details.

Software Factory Schema
The Software Factory Schema defines the core assets that make the foundation of a product line. The schema is always organized around architectural descriptions of viewpoints [5], which describe the system from certain perspectives such as the runtime behavior, logical and implementation structure, component packaging, or physical distribution across network nodes.

Each of the viewpoints contains a description of the assets relevant to that viewpoint, relationships between those assets, the development activities consuming those assets and the artifacts (output) produced by those activities. The Software Factory Schema also describes how the artifacts defined by the viewpoints need to be combined in order to build a concrete product with the Software Factory. It is up to the authors of the factory to define the relevant viewpoints for a particular factory under development.

The SF Schema is therefore a description of what and how we will build and how things fit together. It is created throughout the specification and design phase of Software Factory development. In the near future there will be tools available that are built around a SF Schema meta-model and that allow you to capture the necessary information in a formal way. Therefore the schema effectively becomes a model that allows further processing through model-to-model transformations or code generation (code generation in the broadest sense).

Software Factory Template
The Software Factory Template is installed on the application developer's machine. It customizes the IDE with the guidance, tools, automation etc. that is defined in the schema and enables the efficient development of family members of the product line. Application developers primarily perceive a factory as an extension of their development environment that:

  • Provides them with a starting point and continuous support for developing their solutions.
  • Gives them the reusable component blocks to build the solution.
  • Provides them with guidance on how to build the solution and which activities to perform when.

More Stories By Christoph Wienands

Christoph Wienands is software engineer at Siemens Corporate Research, NJ. He received his Diplom-Informatiker (FH) at the University of Applied Sciences in Furtwangen, Germany. His current research activities include software factories, model-driven development, and domain-specific languages. Due to his research activities he is frequent speaker at conferences such as UML World and SD West.

More Stories By Gunther Lenz

Gunther Lenz is a influential Software Solution Architect/Executive, MBA, published author, invited speaker, and strategic technology visionary with 16+ years of achievements to drive successfully drive software innovation projects. Established technology, process, and organizational transformation agent. Recognized expert in software architecture, big data, and cloud computing. Diverse experience in enterprise, high-growth, and incubation environments within a variety of industries. Published two books and numerous novel articles in the area of software engineering and software architecture. Selected Program Committee Member at prestigious international conferences. Awarded Microsoft Most Valuable Professional for Software Architecture (180 worldwide) 2005-2008. Specialties: • Executive Software Organization Management • Agile/Lean transformation • Innovative Software solutions • Cloud Computing • BigData • Technology Strategy • Technology Evangelism • Research & Development • Author

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SYS-CON Brasil News Desk 04/10/06 10:17:11 AM EDT

There is a lot of commotion and hope around Software Factories in the community today, which was originally sparked by the Software Factories book of Jack Greenfield and Keith Short. The promise is that Software Factories will streamline and automate software development to become more efficient and produce higher quality software. However, at the same time there is a lot of confusion about what Software Factories really are and how to implement them.

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