Discussion

Just to mention some of the several definitions, Hölttä-Otto (2005) defines a module in the context of modular product platforms as “an independent building block of a larger system with a specific function and well-defined interfaces”. Baldwin and Clark (2000) define a module as “a unit whose structural elements are powerfully connected among themselves and relatively weakly connected to elements in other units”. The latter definition has been referenced frequently in the literature since then (Schilling and Steensma, 2001; Ernst, 2005; Arnheiter and Harren, 2005 and 2006; Fredriksson, 2006; Lau et al., 2007). Baldwin and Clark (1997 and 2000) also claim that modularization requires making a distinction

between visible design rules and hidden design parameters; the hidden parameters are encapsulated in the modules, but the visible rules are shared between companies.

Table 3 presents a list of contexts, characteristics and definitions related to modularity mentioned in the earlier literature.

The difficulties of defining the concept of modularity result at least partly from the fact that several research fields have defined and applied the concept for their own purposes. Thus, the concept has been used in many contexts (Campagnolo and Camuffo, 2010; Starr, 2010), at different levels of abstraction, and in different disciplinary areas (Salvador, 2007). Based on his thorough analysis, Salvador (2007) even questions the existence of a single concept of modularity, and concludes that the concept may encompass a number of different, but interrelated, concepts.

Campagnolo and Camuffo (2010) summarized 125 research contributions on modularity in the current literature, and found three main streams of literature. They clustered these around three units of analysis, that is (1) product design modularity, (2) production system modularity, and (3) organizational design modularity. In the literature on product-related modularity, the concept of modularity has been discussed at three levels:

the product, production process, and organizational levels. (Pekkarinen and Ulkuniemi, 2008; Bask et al., 2010a).

Another observation made in the literature is that the definition of a module has often been linked to, and confused with, the benefits sought from modularity (Hölttä-Otto, 2005). The benefits of modularity identified in the literature include managing complexity, enabling parallel processes, and reducing uncertainty (Fine, 2000; Baldwin and Clark, 2000), enhancing customization, product postponement, and outsourcing (Voss and Hsuan, 2009), and a wider variety of products, flexibility, and cost savings (van Liere et al., 2004; Jose and Tollenaere, 2005; Pekkarinen and Ulkuniemi, 2008). Some of the benefits mentioned in the literature are presented in the Appendix.

Literature review

Table 3. Features and definitions presented in the earlier literature on modularity.

Author

"Modular" or "combinatorial" productive capacities are capacities to design and manufacture parts which can be combined in numerous ways

In a modular architecture, interfaces between components are de-coupled and there is a one-to-one mapping between physical components and functional elements

The visible design rules consist of three dimensions: architecture specifies what modules will be part of the system and what their functions will be; interfaces describe in detail how the modules will interact, including how they fit together and communicate;

and standards test a module’s conformity to design rules and measure its performance relative to other modules.

Modularization involves the partitioning of information into visible design rules and hidden design parameters. The visible information is widely shared and communicated whereas the hidden parameters are encapsulated within the modules and need not be communicated beyond the boundaries of the module.

A module is an independent building block of a larger system with a specific function and well-defined interfaces

Mikkola

Four key elements should be considered when assessing the degree of modularity in physical product systems: 1) types of components (ranging from standard to unique), 2) interfaces (whether they are well specified and standardized or not), 3) degree of coupling (i.e. the tightness of coupling among components), and 4) substitutability (i.e. the extent the unique components can be substituted across product families).

Voordijk

In a modular product architecture, components are interchangeable, autonomous, loosely coupled, individually upgradeable and interfaces are standardized. There is clear mapping between functions and components. For a modular product, two factors are thus of major importance: independence of components and interfaces.

Voordijk et al.

(2006)

Process Loose coupling in

time and place Low coupling between the process components in time (production spread over multiple time intervals) Low coupling between the process components in place (production takes place at dispersed locations) Voordijk

et al.

(2006)

Supply

chain Non-proximity

Substitutability High degree of non-proximity of elements (geographical, organizational, cultural, electronic); modular supply chains permit “substitution” of different versions of

functional components for the purpose of creating supply chain variations with different functionalities or performance levels.

Jacobs et al.

(2007)

Product Disaggregation Re-combinability

Modularity is a systems concept defining the degree to which components may be disaggregated and recombined into new configurations

Product modularity is a continuum, describing separateness, specificity and transferability of product components in a product system: 1) “Separateness” = degree to which a product can be disassembled and recombined into new product configurations without loss of functionality. 2)“Specificity”= degree to which a product component has a clear, unique and definite product function with its interfaces in the product system. 3)

“Transferability” = degree to which product components in a product system can be handed over and reused by another system.

Perspectives of modularity: 1) “Component commonality”:a standard kit of components to be used in a number of applications; modular product design consists of using standard parts and subassemblies in a variety of products. 2) “Component combinability” (probably the most commonly understood meaning of product modularity): different product configurations can be obtained by mixing and matching components taken from a given set. 3) “Function binding”: product modules embed the capacity to perform specific functions. 4) “Interface standardization”: focuses on the interface, a set of design parameters describing how two objects mutually interact. 5)

“Loose coupling”: a modular system can be broken down into smaller units, or modules. Remarks: none of the past researchers dealing with product modularity has combined in a single framework all of these perspectives.

Voss and Hsuan (2009)

Service Standardized

interfaces There are five important dimensions associated with the study of modularity: interfaces, degree of coupling, components and systems, commonality sharing, and platform.

With modular services are final services or service packages that can be combined for customers in many ways from one or several distinct components. In this way, customization takes place.

Starr

(2010) General Substitutability, interchangeability of parts

Generic modularity is easy substitution of one thing for another;

services built into goods can be viewed in the same light as modular parts.

Section 2.2. below discusses the relationship between modularity and customization. This issue is also discussed in papers 3 and 5 – from the theoretical and framework building perspective in paper 3, and empirically applying the framework in five cases in paper 5. Sections 2.3-2.6 analyze product, process, organizational and service modularity in order to identify the central issues of modularity. These concepts are also discussed in papers 1 and 2 – paper 1 being theoretical and paper 2 empirical, based on interviews of Finnish LSPs. The following section 2.7 deals with the connections between strategy, business models and modularity at the product, process and organizational levels. These issues are under observation in papers 4, 5 and 6. Finally, section 2.8. presents a summary and concluding remarks on the literature review.