Big Lever Software, Inc.


At the Edge of the Product Line Engineering Envelope
Part 1: Introduction

Greetings from Dr. Charles Krueger, BigLever CEO:

Systems and Software Product Line Engineering (PLE) is a broad, deep and dynamic field. This is true across the spectrum, from applied research to commercial practice. Although the field has been actively expanding since the early days 30 years ago – when we talked about primordial things like application generators and (in my dissertation) modeling and simulating a software architecture design space – at any point in time it has never been clear whether the field was approaching its plateau or whether the envelope of concepts, knowledge, tools, methods, techniques, benefits, and experiences would continue on its ascending trajectory.

Yet year after year we continue to see the envelope expand, where PLE science becomes routine practice, PLE art becomes well understood science, and heretofore unknowns emerge as compelling new art at the leading edge of the PLE envelope. Many of the new advances at the leading edge of practice are visible only to those who are actively engaged in new or expanding PLE deployments, so to increase visibility to the broader PLE community we are kicking off a newsletter series that spotlights some of the compelling new art at the leading edge of PLE.

This newsletter is the first installment in the series, At the Edge of the PLE Envelope.

Multistage Configuration for Product Family Trees

Many of the latest PLE innovations are occurring at the interface between engineering and the larger enterprise, in support of strategic business operations such as product marketing and portfolio planning. In BigLever's 3-tiered PLE Methodology, shown in the illustration, this is the interface between the middle and top tiers. [Click image to enlarge.]

Feature-based methods, using PLE constructs and tools that were traditionally confined to the engineering organization, are proving to be highly effective for product portfolio planning, resource and capacity analysis, and other business facets that need to be explored well before engineering begins.

Multistage Configuration for Product Family Trees1 is a new development at the top (business) tier of the PLE methodology, in direct response to customer needs that only came into clear focus over the last year. It is a good example of emerging practice at the edge of the PLE envelope. Multistage configuration trees support complex product family trees, where feature decisions are incrementally staged throughout the nodes in a product family tree. Feature decisions made at any node are inherited by all descendants of that node, thereby defining a product family subtree.

In successful commercial product line organizations, the number and diversity of products delivered can grow to be extremely large, partially due to the efficiencies made available by the latest generation of PLE tools and methods. In market segments ranging from automobiles to industrial systems, it is not unusual for companies to manufacture millions of products every year, in thousands of different "flavors". This extreme product line diversity creates major challenges for engineers implementing the product line, product marketers defining the space of available products, and customers selecting from the array of available products. To provide order and clarity about their product groupings and offerings within this type of complex product space, enterprises often organize their products into a product family tree.

Multistage configuration trees is a result of applying the product family tree concept to feature management in PLE. A systems architect from a customer made an insightful comment that illustrates how this represents a different way of thinking: "We are more focused on identifying the features that we don't want in a particular [subfamily] than we are on specifying the features we do want on any particular product." In other words, the internal nodes in a product family tree are more important than the product nodes at the leaves of the tree. Contrast this to the traditional PLE focus on techniques for selecting and solving for features in a product instance.

In multistage configuration trees, a traditional feature model (the full collection of feature choices available in a product line) serves as the root of the tree and fully bound feature profiles (feature choices made for each particular product instance) are found at the leaves of the tree. A new construct is introduced for the internal nodes of the tree – the partially bound feature profile – where some feature decisions have been made or restricted and other feature choices remain available.

A partial profile is more than just a partially filled out feature profile. There are special semantics for unbound and downselected feature decisions.

  • Unbound means that the modeler has explicitly made their decision to leave a decision open, so that other descendants in the multistage configuration tree can make their own decision – possibly different in different subfamilies – about this feature choice.
  • Downselection reduces the available diversity for a feature, while still leaving some diversity open in an unbound decision.

For example, this screen shot provides a view of an expanded feature-based product family tree -- including feature downselection, selection and inheritance -- for a home heating and cooling system. [Click image to enlarge.]

Any connected path from the root node to a leaf node must be a monotonically non-increasing sequence in the space of available feature choices. That is, children must honor the feature decisions made by their ancestors and may optionally decide to make additional feature decisions that further constrain the space of available feature choices.

Multistage configuration for product family trees has broad applicability for scenarios across different systems and software engineering domains, including:

  • In aerospace and defense, defining subfamilies for exportable versus legally restricted, non-exportable feature content
  • In automotive, organizing the millions of product instances that need to be produced each year into a tree of manufacturing platforms, models, regional configurations, trim packages, and user offerings
  • In consumer electronics, structuring different product levels, from low-end to high-end
  • For OEMs, maintaining strict separation among customer-specific proprietary intellectual property

Multistage configuration for product family trees is one of the most influential new concepts to emerge at the leading edge of the PLE envelope. It is being adopted by new and strategically important organizational roles for PLE – by people who analyze, plan and define product portfolios. These roles have traditionally been dealing with their complex product family tree issues using things like large and intricate spreadsheets, so adopting formal PLE concepts, languages and tools provides significant enhancements to the way they work. One organization is starting their PLE transition here, moving the typical PLE adoption beachhead one step upstream from the engineering organization.

Stay tuned for more installments in the series, At the Edge of the PLE Envelope.

Best Regards,

Charles W. Krueger
BigLever Software CEO

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Patent Pending