=Paper=
{{Paper
|id=Vol-2220/08_CONFWS18_paper_10
|storemode=property
|title=Do You Read Me? On the Limits of Manufacturing Part Numbers for Communicating Product Variety
|pdfUrl=https://ceur-ws.org/Vol-2220/08_CONFWS18_paper_10.pdf
|volume=Vol-2220
|authors=Aleksander Lubarski,Frank Dylla,Holger Schultheis,Thorsten Krebs
|dblpUrl=https://dblp.org/rec/conf/confws/LubarskiDSK18
}}
==Do You Read Me? On the Limits of Manufacturing Part Numbers for Communicating Product Variety==
https://ceur-ws.org/Vol-2220/08_CONFWS18_paper_10.pdf
Do You Read Me? On the Limits of Manufacturing Part
Numbers for Communicating Product Variety
Aleksander Lubarski1,2 and Frank Dylla2,3 and Holger Schultheis3 and Thorsten Krebs2
Abstract. Manufacturing part numbers (MPNs) are used to In this context, alphanumeric strings have been used to
communicate product variety both for internal purposes and for communicate product variety both for internal purposes and for
external representation to customers. To simplify this external representation to customers [4]. For referring to these
communication, MPNs have been originally developed as human- strings various denominators are common practice, e.g., type code,
readable abbreviations of those characteristics that uniquely identify order code or ID, part ID or number. For reasons of simplicity, we
a product variant out of a modular system, thus acting both as an will use the term manufacturing part number (MPN, see Section 2.3)
identifier and a description. However, the increasing complexity of throughout this paper. MPNs are codifications of product
customer requests forces component manufacturers to expand their
product portfolios, thus pushing the descriptive character of a classic
MPN to its limits. Ongoing digitalization drives product
identification towards fully-digital possibilities. Nevertheless, in
reality component manufacturers still rely on MPNs. Against this
background, the purpose of this paper is to analyze the cognitive and Figure 1. Exemplary MPN structure for a rotor system (Lautner GmbH)
systemic characteristics of the MPN with regard to the underlying
product structure (PS). As a result, we derive evaluation criteria for characteristics or functions (e.g., information on its structure,
the quality of mappings from PS to MPN and apply them to typical
material composition, production process) and act as a distinct
business use cases. In doing so, we provide the first systematic
identifier of a certain product combination (Figure 1). Typical use
overview and discussion of factors that determine MPN’s utility and
usability as well as give practical guidelines for component cases for MPNs range from initial product search to reordering or
manufacturers regarding the selection of appropriate MPN types. 1 23 maintenance of a particular machine. Within this paper, we focus on
the appropriateness of such numbers for the purpose of
communicating product variety, i.e., visible features. In practice,
1 INTRODUCTION oftentimes the corresponding stakeholder is provided with relevant
supplementary documents that explain the structure and the logic of
With the growing trend of customization and the overall direction
the MPN and accelerate the process of “deciphering” its information
towards a lot size of one, manufacturers are facing new requirements
(e.g., tables, graphs, dictionaries). However, although originally
of representing their product portfolio in a clear and structured way,
developed to be human-readable in order to simplify the customer-
as well as understanding their customers’ demands. This is a concern
supplier communication, we ask the following questions, since
particularly in the business-to-business (B2B) markets, where
many things have changed:
complex machines (and even machine parts) consist of numerous
• Is it still necessary and monetarily reasonable to use MPNs that
modular elements, thus offering almost unlimited configuration
are human-readable 4?
possibilities to the customers. For example, compared to a BMW • Where are the limits of different MPN types and what should
series 7 who offer as many as 1017 possible variants [1], Lenze AG the selection of the appropriate MPN depend on?
claims to have up to 1030 configuration possibilities just for their In particular, there exist various reasons to switch to a completely
gear motor, each of which resulting into a separate identifier. digital MPN. First, the descriptive character within any human
However, if not structured properly, an unnecessarily high product interaction works only as long as a certain length and complexity of
variety can become counter-productive, since customers can get the MPN is not exceeded [5]. For products with a rich variety the
confused about the differentiation among product variants [2]. In number of product characteristics and, consequently, configuration
this way, while a modular product structure promises a compromise possibilities, is very high. In this way, at some point, the MPN may
between customer-driven customization and manufacturer- become too complex and confusing for involved stakeholders. In
motivated standardization [3], the structuring and the case a customer is not able to fully understand how a specific MPN
communication of “what’s possible and at what price” is a very relates to the corresponding product may result in delays or incorrect
important, but also a challenging task. orders, potentially damaging the customer-supplier relationship.
1 4
Industrial Services Group, University of Bremen, lubarski@uni-bremen.de In this publication we define “human-readable” as the code feature to be
2
encoway GmbH, {aleksander.lubarski, frank.dylla, krebs}@encoway.de read and comprehended by the human, while “machine-readable” or
3
Bremen Spatial Cognition Center, University of Bremen, “digital” can be processed solely by a digital medium
{dylla, schulth}@informatik.uni-bremen.de
Second, since B2B customers have to deal with dozens of such PS mapping are explained in Section 3. The evaluation criteria are
structures a day from different suppliers, they are no longer willing then applied to the typical business use cases in Section 4. The paper
to invest their time in understanding the internal product structure of concludes with a summary of the results, possible limitations as well
each of their partners [6]. This leads to the overall decline of the as future research opportunities.
technical know-how in the market, thus making human-readable
MPNs containing these technical details rather obsolete. Third,
company mergers and acquisitions may result in inconsistencies and 2 THEORETICAL BACKGROUND
redundancies in the data management 5 [7]. On the one hand, both
companies could have similar nomenclatures (or even same serial 2.1 Code Function and Code Word
numbers for different products), thus causing confusion for the
future product handling. On the other hand, the customers of the In general, a code is an agreement on sets of meaningful symbols for
company would get an additional structure to deal with, thus the purpose of information exchange between a sender and single or
increasing the complexity of variant management and multiple recipients (e.g., [10], [11]). For this purpose, the sender
communication. encodes the information, which needs to be decoded by the recipient
Nevertheless, despite all advantages mentioned above, it would with the same coding schema. From a mathematical perspective, a
be narrow-minded to claim that a digital (i.e., only machine- code is an injective mapping from a domain element (𝑥𝑥 ∈ 𝐷𝐷) to an
readable) MPN is a universal solution for the efficient element of an image set (𝑦𝑦 ∈ 𝐼𝐼). Furthermore, the resulting image
communication of the product variety for every manufacturer. The must not be empty:
most obvious argument against the abolishment of human-readable 𝑓𝑓: 𝐷𝐷 → 𝐼𝐼 +
MPNs is the complete dependency on a digital device (e.g., QR code In the context of codes 𝐷𝐷 and 𝐼𝐼 are considered finite alphabets, i.e.
reader, barcode scanner) to read and understand the MPN. Examples arbitrary sets of symbols with a limited number of elements. In
of situations when this could be problematic include product general, codes can be applied for abstracting or abbreviating
manufacturing, where a person using an MPN as a guideline for information and its dependencies. In that sense, not only the Morse
assembly would have to interrupt the production process, or general code or the internet acronym LOL (“laughing out loud”) is a code,
network coverage problems leading to the inability to use a central but also traffic lights.
referral database. As for other non-functional requirements, the From a communication perspective, a code is a translation from
transition to the digital MPN would result in additional hardware- the sender’s original information or message to some
related costs as well as general efforts for restructuring. Moreover, communication means (encoding or encryption), e.g., digital
such an initiative could also meet the opposition of the users impulses, sound or flags. If the code function is known to the
themselves, who are generally reluctant to any structural changes, recipient, the original information becomes easily decodable
since they are used to the way the things are currently handled [8]. (decoding). Otherwise, the recipient is not able to restore the
Finally, since a digital MPN has all the freedom regarding how much information at all (no decryption possible). Each code word (a
information it can hold and thus communicate, product sequence of symbols), which is derivable by the code function, is
manufacturers might get tempted to put too much information (if not called a valid code word. Following these definitions, the transfer
all of it) in one single digital ID, e.g., a QR-code, thus overwhelming from a product structure (PS), i.e., simplified a set of product
their customers, who would spend additional time for finding the characteristics with certain values, to some part number, e.g. an
relevant information [9]. MPN. The code function is the schema which characteristics are
Overall, while digital identifiers such as RFID integrated into considered and how the corresponding values are represented in the
ERP systems have been proposed more than a decade ago, the reality resulting code word, i.e., a product-specific MPN. In the remainder
shows that product and part manufacturers are still far away from of the paper, in general, we will not distinguish between the code
the best practice, which calls to find out why. Motivated by the function and the resulting code word and use the term ‘code’
heterogeneity of the involved stakeholders and an overall specificity synonymously.
of product configuration in the B2B markets, we believe that The application of codes is closely related to efficiency, which is
different MPN structures are needed depending on respective achieved by reducing complexity regarding the original information,
application scenarios. Therefore, by applying methods from i.e. by abstraction, abbreviation, or compression. As it takes the
information theory and insights from cognitive science we analyze effort to design a code, a code gets more efficient the more often it
relevant characteristics of MPN as well as define evaluation criteria is used. Additionally, some codes use a modular architecture (i.e.
for how well the MPN can map the underlying product structure decomposition of a complex system in separate functional units) for
(PS). By showing that there exist five typical business use cases and reasons of efficiency.
thus no universal MPN we contribute to the theoretical discussion With this theoretical background in mind, we consider the
on knowledge representation and pave the ground for further relation between code functions and MPN generation from a
research. In addition, as current pragmatic solutions of the psychological perspective in more detail in Section 3.
practitioners are rather narrow-minded without considering their
efficiency, we give practical guidelines for the selection of an
appropriate MPN. 2.2 Variant Management
The remainder of this paper is organized as follows. After giving Due to a high level of heterogeneity and a tight customer
a short overview of the theoretical background in Section 2, the involvement both in the product design and manufacturing [12],
aspects of MPN and PS, as well as evaluation criteria of the MPN-
5
Project experience of the authors shows that these kinds of problems may
arise even between units of the same company.
B2B manufacturers are constantly searching for new ways of universal definitions or terminology. The challenge lies in the
standardization without diminishing their ability to go the last mile applied nature of the topic and its historical development – not only
for their customers [13]. In this context, the introduction of the do the terms and labels differ between companies (especially across
modular product design (i.e. building a complex system out of different domains and fields of operation), but sometimes even
exchangeable modules with a clear function and defined within the same company, depending on the department and the use
connectivity interfaces) has led to a series of organization and case. For example, the term “type code” is often used for the
production changes, thus expanding configuration possibilities description of product groups, even though this term has already
almost exponentially [14]. This resulted in the introduction of such established itself in the context of digital storage media, e.g., DVD
manufacturing concepts as Mass Customization [15] and an overall and Blue-ray [20]. Other misleading terms for the same purpose
higher interdependence of the supply chain partners. include “Product Key” or “Type Designation Key”, which are used
However, while a modular product structure promises a either when installing software programs or when describing
compromise between customer-driven customization and specifications and configurations of computer drives [21]. The fact
manufacturer-motivated standardization [16], the variant that there exists no standard (international) specification or central
management throughout the whole product lifecycle becomes point of reference makes it even more confusing for the
increasingly challenging. A good overview of the sources of communication with partners and customers.
complexity in engineering design and manufacturing is given in [5], Irrespective of the use case, each product or service needs a
where complexity is considered as a multi-faceted measurement that certain description for the purpose of identification and explanation,
is influenced both by endogenous and exogenous drivers. containing compressed information in the form of characteristics.
ElMaraghy et al. [17] define variety as “a number or collection Oxford Dictionary defines Identifier (ID) as a sequence of characters
of different things of a particular class of the same general kind”, used to identify or refer to an element, such as a variable set of data.
with a variant being an instance of a class that exhibits (slight) Such an ID can refer either to a unique class of objects with a certain
differences from the common type. The overall goal of modular level of abstraction (i.e. products that are grouped based on a certain
product structures is the minimization of inner variety while set of characteristics while, possibly, ignoring further details), or be
maximizing outer variety. In other words – to offer customers as used for an identification of a specific physical object. A typical
many individualized products as possible with as few parts in example of the object identification is a serial code or Serial Number
production as possible [16]. Additionally, when talking about (SN), which is usually comprised of numerals even though other
variant management it is reasonable to differentiate between its two typographical symbols are also possible. In most cases, the SN is
levels – strategic and operative. While the strategic level built with no particular logic or predefined structure, as it is assigned
concentrates on “determining and mastering the variety of the incrementally or sequentially to an item in the production [22] and
product portfolio in such a way that it is aligned with the competitive thus cannot be read or interpreted by any of the stakeholders. On the
and the product strategy”, the operative level implements and contrary, Manufacturer’s Model Number (MMN) is a solely
secures the overall variant strategy [18]. This publication focuses on marketing-driven succinct and catchy description with the purpose
the operative level since MPNs are used for the identification and of evoking certain associations and interpretations when being
representation of a certain product instance or a category of product communicated to the customers. However, the inevitable problem
combinations, thus supporting the actual implementation of variant with the MMN is its necessary level of abstraction – driven by either
management. At this point, we assume that a modularization process customer’s cognitive capacity (e.g., the ability to remember a certain
has already been conducted and a modular product structure is string) or system limitations (e.g., input fields of ERP systems are
already given as an input. More information on these steps can be often limited in length), the MMN has to concentrate only on the
found in [16]. most important product characteristics (e.g., iPhone SE 64 GB
The challenge of operative variant management resulted in the black) thus neglecting other valuable product information [4].
emergence of a specific market for so-called CPQ-systems [19], Against this background, a compromise between production-
which can be integrated into existing enterprise software. CPQ driven machine readability and marketing-driven human-readability
software enables product configuration (C), its respective pricing (P) can be reached by using the term Manufacturer’s Part Number
and creation of a unified quote containing all necessary information (MPN) [23], which is the focus of our publication (Figure 2). While
of the offer (Q). While these quotation documents contain all the also being an identifier for a unique class of objects just like MMN,
details about the desired machine or its component, MPNs are a the MPN contains much more information and is historically built
more compact information representation used for internal and upon a certain predefined structure, which is often sent directly to
external communication of the product variants and variant the customer. 6 Here, an SN is a particular instantiation of an MPN
identification. As of today, both the topics of CPQ-systems and acting as an identifier within a certain context. Therefore, an SN
MPNs have not been devoted enough academic attention, even alone cannot be used as a unique identifier (UID), i.e., guaranteed to
though they are used in practice on an everyday basis. be unique among all identifiers used for those objects and for a
specific purpose, as companies may have identical serial number
systems for different products within their product portfolio. Instead,
2.3 Product Identifiers a UID can be created by combining both the MPN and its particular
Since the topic of variant management and product identification instantiation SN, e.g., “Model X” and “Serial Number 238912”.
involves different research disciplines such as engineering, From a mathematical point of view, an MPN is a code word, which
marketing, information systems or even psychology, there exist no
6
For example, the manufacturing company SEW has a 15-page document
showing the structure of their MPN.
the MPN. In this way, it was possible to show that there exists no
universal MPN, but rather that its selection depends on certain
industrial, company, and customer characteristics (Result D).
3.2 Formal definition
Figure 2. Different identifiers and their interrelationship While it may seem that an MPN is just a string of characters, it has
numerous systemic and cognitive aspects, which influence its
is derived by a code function from the product structure taking a
communication and variant management in general. In this context,
subset of characteristics into account (cf. Section 2.1).
MPN generation can be seen as a specific mapping ℳ that is used
to represent a given (fixed) product structure in an understandable
3 MPN-PS MAPPING EVALUATION way (cf. Section 2.1), aiming to be both complete and easy to use
(Figure 4). With different product structures and company’s
specificities, there are many ways to approach such a mapping,
3.1 Methodology ranging from a mere enumeration of all possibilities up to the
complex nested configurable structure, meaning that the quality of
For the purpose or transparency and traceability of our results, we
the mapping can be evaluated for a specific context. We define such
first give an overview of the methodology used in this paper (Figure
an evaluation function ℰ of mapping ℳ with respect to a specific
3). It consists of the metaphases Orientation and Application of the
need or application of the generated MPN, defined by a set of
MPN, each containing two consecutive steps along with the applied
evaluation criteria 𝒄𝒄 = [𝑐𝑐1 , … , 𝑐𝑐𝑚𝑚 ] and corresponding outcomes 𝒙𝒙 =
technique (textual description) and preliminary results (rectangles).
[𝑥𝑥1 , … , 𝑥𝑥𝑚𝑚 ]:
ℰ(ℳ, 𝒄𝒄) = 𝒙𝒙 𝑤𝑤𝑤𝑤𝑤𝑤ℎ 𝑥𝑥𝑖𝑖 ∈ [0. .1]
Based on the insights from the expert interviews (Figure 3, Step 1)
and literature review (Figure 3, Step 2), in this publication, we
concentrate on the general mapping ℳ and the definition of the
corresponding evaluation criteria as well as their testing for different
use cases. The subsequent optimization problem, i.e. finding an
optimal MPN with respect to a given set of criteria, is beyond the
scope of the publication and is left for the future research.
Figure 3. Overall paper methodology
Due to the applied nature of our research, first, we contacted the 3.3 Product and MPN structure
practitioners in order to identify current problems in variant
When talking about the evaluation of the MPN it is important to
management and product configuration (Step 1). For this, we
differentiate between two different types of structure (Figure 4).
cooperated with one German consulting company, which specializes
The Product Structure is a rigid arrangement of elements that is
in CPQ-Software for complexity reduction and simplification of the
used to depict product compositions and configuration possibilities.
quotation process. By conducting semi-structured expert interviews
Unlike the MPN structure, the actual product structure (i.e. what
[24] with eight of its previous customers, we were able to gather first
elements a complex machine consists of, what possible
insights on the challenges concerning MPN and confirm that
combinations are there, etc.) states the core of the value proposition
different use cases require different types of MPN (Result A).
and thus cannot be changed. In this regard, the Number of Product
As a second part of the orientation phase, we then conducted a
Characteristics shows which parts of a complex product can be
systematic literature review (Step 2). Sadly, despite its practical
substituted or exchanged if desired. Similarly, such a modular
importance, the topic of MPN structure and its deployment has not
product composition and interface specifications determine the
received enough academic attention yet. Therefore, in order to place
Configurable Variety, thus enabling satisfaction of customer
our research within an ongoing theoretical discussion, we also
heterogeneous requirements. However, as mentioned earlier, a
looked at the adjacent topics of variant management, complexity in
manufacturing, and production identifiers. In this way, we were able
to identify various MPN aspects, which are relevant for the
communication of the product variants (Result B).
The second phase dealt with the application of the MPN in the
real-life context. For instance, based on the results from the
orientation phase we were able to derive systemic and cognitive
evaluation criteria for the MPN-PS mapping in Step 3 (Result C).
Since this publication is meant to open a discussion on the topic, we
did not provide any specific metrics but remained merely on a
conceptual level. Finally, with the help of the conducted expert
interviews and based on our own experience from previous projects
in Step 4 we defined five business use cases for the MPN
deployment, including stakeholder description and requirements for Figure 4. Depiction of the product structure with the use of MPN
higher configurable variety does not necessarily mean a better preferences, the human user should be able to map the MPN to a
portfolio, since an excessively high variety can even be counter- corresponding product 1) quickly, 2) with acceptable accuracy, and
productive, as customers can get confused about the differentiation 3) without extensive learning. A prerequisite for achieving this is
among product variants. Finally, the actual Composition of the MPN that the MPN and the mapping realized by it are conducive to the
along with the sequential arrangement of the characteristics within way in which humans process information. For example, consider
is influenced by the product structure. In other words, the the acronym "TDI" to characterize a property of car motors. If
stakeholder is able to read and understand the information encoded confronted with this acronym in the context of cars, people may
in the MPN only as long as he/she knows what symbol is responsible already "know" that the car being under consideration has a diesel
for what characteristics. motor with "Turbocharged Direct Injection". 7 At this point, the
The MPN structure, on the other hand, is flexible and can be question arises: how or why do people know this? If observed
adjusted according to the company’s preferences. A cleverly picked separately, these three letters "TDI" could also stand for something
MPN can enhance human understanding and thus its overall else, e.g., "Total Dream Interior", thus describing some arbitrary
manageability and understandability, whereas a bad MPN may aspect of the car. The only source for this knowledge is the memory
confuse both the company employees as well as their customers. of the person having to deal with the acronym. In other words – the
This includes the Length of the MPN, which may sometimes be working and usability of MPNs for human users relies critically on
challenging, since many ERP systems (e.g., SAP) have an integrated the memory capacity of the human user.
limit on the string length, thus indirectly forcing product The human cognitive system is commonly conceived as
manufacturers to use shorter codes [4]. Another important MPN consisting of several different types of memory stores [25]. For
characteristic is an average Characteristics Richness showing how reasons explained in the following, the two types of stores most
many variants are encoded inside single characteristics. This aspect relevant for our considerations with regard to MPNs are working
is especially important if the MPN is human-readable and a person memory (WM) and long-term memory (LTM). Information recently
operating it has to remember all the variants of every characteristic having or currently being processed resides in WM. As such, WM is
by heart. Finally, the amount of configurable feasible solutions is assumed to be limited in capacity as well as in the duration that
limited by the applicable logical rules (e.g., IF, XOR, AND), which content will remain accessible. Although exact estimations vary it
can be summarized by the aspect Dependency Density. Although seems clear that no more than 10 items of information can be
acting as a limitation to the possible solution space, dependency maintained simultaneously [26, 27]. If the information in WM is not
density increases the complexity of the MPN and thus its used, it will be lost within a few seconds [28]. Human LTM, on the
applicability by a human stakeholder. Looking at the long-term life- other hand, can store vast amounts of information (see [29] for
cycle of products, another central aspect is the Extensibility of the estimates) over very long time spans (just think of old people telling
MPN. This is particularly important for products, which are still in stories from their childhood). In fact, depending on the usage
the development and it is foreseeable that new characteristics may frequency, information from LTM can be retrieved into WM and
be added according to customer’s preferences or market’s information residing in WM may be transferred to LTM for more
development, e.g., by adding functionality by software updates. The permanent storage. Going back to the "TDI" example, it seems most
level of extensibility can hereby range from practically impossible likely that knowing that "TDI" signifies "Turbocharged Direct
(e.g., rules defining the MPN structure prohibit any further Injection" is retrieved from LTM. If it was not the case, it would
extension) or cost-inefficient (e.g., requiring database connectivity) have had to be maintained in WM since first learning what "TDI"
to complete freedom (e.g., no limitations within a digital MPN). means. This may be the case when someone first tells you what
Finally, the choice of MPN Representation type predefines how it "TDI" means in the domain of car motors, but on later encounters, it
will be used between the involved actors. Three possible types of seems unlikely that the meaning of the acronym has been constantly
MPN representation can be differentiated, each with its advantage maintained in working memory for the whole time. Given that LTM
and limitation: (i) human understandable MPN that can be read and plays a central role in the human use of MPNs, it is instrumental to
assessed without any additional help, meaning that human operator consider some of the properties of how information is represented
needs to know the MPN structure and characteristic meaning by and organized in LTM. Two properties seem particularly
heart; (ii) human readable MPN that can be read and assessed using noteworthy.
a certain (analog or digital) code translator or additive requiring a First, human LTM is associative [30]. Certain concepts/pieces
certain level of know-how of the user; (iii) machine-readable MPN of information are associated with each other such as, for example,
that can contain almost unlimited amount of coded information the concept of "fire" is associated with the concept of "heat". In
within product characteristics, without any know-how requirements particular, these associations are a major means of retrieving
for the user, but with a high dependency on a digital scanner.
information from LTM. If a current item in WM is sufficiently
strongly associated with some other piece of information in the
3.4 Mapping evaluation criteria LTM, retrieval of this other information is greatly facilitated. If, for
instance, "TDI" is sufficiently strongly associated with
Once an appropriate MPN and a clear mapping of the product
"Turbocharged Direct Injection" in the context of cars, seeing the
structure to the MPN is created, the question arises how well a
human can employ it, with or without any auxiliary means, i.e. how acronym will allow retrieving the desired information.
complex the code function is w.r.t. human processing (cf. Section
2.1). If we abstract from specific company restrictions or personal
7
Due to its direct connection to the fuel type Diesel it is also considered as
“Turbocharged Diesel Injection”.
Second, knowledge organization in human LTM is hierarchical • The more easily (parts of) the MPN can be maintained in
[31, 32]. This means that human LTM has a tendency to be working memory,
organized into categories, subcategories, and concrete instances. If • The fewer associations have to be memorized,
asked to enumerate properties/instances in a certain domain, people • The more previous knowledge can be drawn on, and
will often enumerate aspects (sub)category after (sub)category. Vice • The clearer it can be structured hierarchically.
versa, if people are asked to memorize a (large) list of properties, the
ability to memorize the given information increases considerably, if
3.4.2 Processing speed
the material can be (and is) organized hierarchically. Having
expounded the crucial characteristics of human memory, we now Processing speed can be assumed to be directly related to the length
relate them to the readability, learnability, and processing speed of and the complexity of the MPN: The shorter the MPN and the less
MPNs. complex (i.e., the fewer associations) the faster the human user will
be able to map the MPN to the product. Direct mappings can be
assumed to be faster than hierarchical mappings, because each level
3.4.1 Readability / Learnability in the hierarchy requires a separate mapping, while a direct mapping
– once sufficiently learned – involves only a single mapping process.
In the context of this publication, we consider an MPN readable, if If a hierarchical MPN is employed, the order in which MPN parts
a human user can map each MPN to the corresponding product (a) signifying different (sub)categories appear in the MPN will have an
virtually without error and (b) without any supporting material (e.g., influence in processing speed. At least in western culture languages,
tables, software). Thus, the following requirements have to be met: representing highest to lowest (sub)categories by MPN parts ordered
• The MPN has to be short enough to be held in WM completely from left to right (the predominant reading direction) will likely lead
or it has to consist of several meaningfully separable parts, each to faster MPN processing than other orderings. Consequently, the
of which is short enough to be held completely in WM. processing speed of MPN increases
• The MPN or its meaningful parts have to be sufficiently • The shorter the MPN,
strongly associated in LTM with the product aspects they • The fewer associations are involved,
represent. • The fewer hierarchical levels are involved, and
The first requirement seems comparatively easy to achieve. A ten- • The more the ordering of the hierarchy levels in the MPN
arity code using letters and ciphers is able to represent about 3510 corresponds to the reading direction.
different product variants. The second requirement is tightly related
to the learnability of the MPN, that is, to the feasibility of acquiring 4 USE CASES
all necessary associations and the speed with which they can be Motivated by the diversity of the customer requirements and
acquired. As a result, the second requirement is much harder to specificity of product configuration in the B2B markets, we propose
satisfy as soon as we are dealing with large-scale variant spaces. five different application scenarios also referred to as “use cases” in
There seems to be an upper limit of only around 5000 arbitrary the context of business modeling [34]. The use cases are based on
associations that human LTM can store, while learning a good 3000 the expert interviews and insights from the previous projects (Figure
arbitrary associations took a whole year (incremental training with 3). To ensure comparability, we describe each of the use cases using
three sessions each day) [33]. If the human user is supposed to go following characteristics: (i) role of the involved actor, (ii) his/her
aim and objective, (iii) current know-how level in the field, as well
beyond such limitations, the code either needs to build on and reuse
as (iv) what is expected from the desired solution. Consequently,
existing associations or the code has to be organized hierarchically
with the help of the previously introduced evaluation criteria, we
or both. The simplest form of reuse is to employ non-arbitrary derive individual MPN requirements for each of the use cases (Table
mappings. For example, in the case of "TDI" the acronym is much 1). For simplicity reasons, the costs relating to the implementation
easier to memorize than arbitrary acronyms (e.g., "XYZ"), because and maintenance of a specific type of MPN (e.g., establishing the
the letters in the acronym are the starting letters of the crucial words new MPN structure, employee training, structure maintenance) is
in the product description and, thus, the letters are already associated beyond the scope of this paper but should be considered in future
with the target words. More elaborate forms of reuse may involve research.
exploiting more domain-specific knowledge of the human users. A Starting with the customer side, one particular type of users is a
hierarchical organization of the code would allow reducing the Rare Guest, who is characterized by a low frequency of MPN use
number of associations that need to be stored at each level of the and the need for a specific (one-time) solution. These customers
hierarchy, while still allowing to cover a large variant space with the have little to none expert knowledge on the topic, either because of
MPN. For example, the first digit of the MPN may signify whether the involvement in various supply chains or due to the overall
the product is a car or a motorbike with the remainder of the key then unwillingness to deal in detail with the product structure of the
being specific to the type of vehicle (car or motorbike). The upper particular manufacturer. Their expectation towards the
limit of possible associations that can be stored when drawing on communication of product variety is a mere satisfaction of their
existing knowledge and hierarchical organization is hard to predict request with as little effort as possible. In this way, the rare guest
and will probably also depend on the individual user. Nevertheless, would not appreciate the efficiency of the MPN (e.g., through the
it is clear that the readability/learnability of the MPN increases: digitalization), but would be disappointed if standard functionalities
are not functioning properly. At the other end of the spectrum, there
is a Power User. Unlike the rare guest, the power user deals with the
respective MPN on a regular basis. Due to the high level of know- Finally, the employees working in the internal Production
how both regarding the operating industry and the MPN structure, department of the company are looking for an MPN, which would
the power user is interested in a fast interaction and comparability of both contain information on the internal structure of the product and
different variants within this particular manufacturer, in order to have a high level of learnability. Their daily usage of the MPN
involves the identification of the required parts and their assembling
attain the optimal solution for a specific situation. Typically, power
sequence. With a highly specific background knowledge and fast
users are established via long-term cooperation between companies
production processes, production employees would appreciate a
and would be interested in a high learnability of the MPN. Moreover, digital MPN only if it can assure a low error rate and not obstruct or
they personally would even get averse to switch to a purely machine- slow them down in their daily activities.
readable MPN, since this would make their own know-how obsolete.
The last external stakeholder of the MPN we consider is the
Purchasing department, who already has a particular product 5 CONCLUSION AND OUTLOOK
configuration in mind. Similar to the rare guest, the purchasing With the increasing customer demands for individualization and an
department has little interest in the product itself (or its overall growing complexity of B2B products, part manufacturers are
configuration), but mostly focuses on getting the best price and most facing new problems of communicating their product variety in a
suitable delivery time. In addition, due to the overall desire for transparent and efficient way. In this context, MPNs are used as
comparability across different manufacturers, the purchasing codifications of those characteristics that uniquely identify a product
department seeks understandability and simplicity of the MPN and, variant out of a modular system, thus acting both as an identifier and
if possible, the establishment of an industry-wide standard. a description. While academia has not yet devoted enough attention
Apart from the customer-driven requirements towards the MPN, to the topic of MPN, we believe that a correct deployment of the
manufacturer’s internal departments have their own, often MPN is a key step to efficient variant management. Therefore, in
contradictory expectations. For example, the Sales department uses this publication, we analyzed the main systemic and cognitive
MPN for selling, searching, and configuring product variants in a aspects of the MPN and derived evaluation criteria (i.e. readability,
simple and quick manner. Similar to the purchasing department of learnability, and processing speed) for its mapping on the underlying
the customer, the internal sales department seeks a practical and product structure. We then mapped these evaluation criteria on
catchy MPN structure, which can be used for the external various use cases of the internal and external stakeholders, thus
representation of a large quantity of (homogeneous) products. With showing that there exists no ideal MPN, but instead it should be
the level of know-how varying according to the position and the created depending on the respective application scenario.
seniority of the sales employees, the efficiency of the sales This publication also highlights important topics for future
department is dependent either on the learnability of the human- research endeavors. First, despite a detailed analysis of the existing
readable MPN or on the increase of the processing speed due to its literature on manufacturing complexity combined with personal
digitalization. project experience of the authors, we believe that there exist
additional aspects of the MPN and the product structure. Similarly,
Table 1. Various use cases regarding the deployment of MPNs
External Internal
Role Rare Guest Power User Purchasing Sales Production / Logistics
Goal Identification, Identification, Acquisition, Sale, searching, Overview of the
searching, searching, reorder configuration internal structure
configuration configuration
Use case description
Use Case Solution of an Finding an optimal Best price and Suitable product, Fast identification of
application variant for a delivery time possible large the required parts and
problem specific situation quantity their assembling. Low
error rate
Know- Low background High background Little interest in the Diverse (internal High background
How knowledge knowledge product vs. external sales, knowledge (highly
seniority) specific)
Desired Description of the Fast interaction, Comparability Same description Fast transfer (e.g.,
Solution problem, not comparability of across different of the homogenous location of a product
technical detail the variants manufacturers products part)
Read- No preferences, as Human-understan- Type of readability Catchy type and Human-understandable
ability long as it dable (without any that enables structure that can (without any auxiliary
functions right auxiliary means) supplier be used for means)
MPN requirements
comparability marketing
Learn- Not needed, since High expectations Not needed, since High expectations High expectations
ability no intentions for towards the logic of no intentions for towards the logic towards the logic of
reuse the MPN structure reuse of the MPN the MPN structure
structure
Process- No preferences, as Crucial to the Preference Preference Crucial to the
ing speed long as it efficiency of their direction machine- direction machine- efficiency of their
functions right everyday work readable MPN readable MPN everyday work
future work should differentiate between industries or company- [13] A. Bask, M. Lipponen, M. Rajahonka, und M. Tinnilä, „The concept
specific characteristics. of modularity: diffusion from manufacturing to service production“, J.
Altogether, our publication has no claims to completeness but is Manuf. Technol. Manag., Bd. 21, Nr. 3, S. 355–375, 2010.
intended to serve as a starting point of an academic discussion on the [14] C. Y. Baldwin and K. B. Clark, Design rules: The power of modularity,
MPN and the communication of the product variety in general.
Bd. 1. MIT press, 2000.
Future research should focus more on the differentiation between
[15] B. J. Pine, Mass customization: the new frontier in business
different layers of the company, in particular, the production and the
competition. Harvard Business Press, 1999.
sales layer, which may even lead to different MPNs. Another
research direction is the operationalization of the above-mentioned [16] A. Lubarski und J. Poeppelbuss, „Methods for Service
mapping by introducing a maturity model [35] or some other Modularization–A Systematization Framework“, in Proceedings of the
decision-support framework. This may also include the task on how Pacific Asia conference on information systems (PACIS), Chiayi,
to find optimal MPN for a specific set of criteria. A good opportunity Taiwan, 2016.
for creating such a model would be by following an action research, [17] H. ElMaraghy u. a., „Product variety management“, CIRP Ann., Bd.
where the transformation of the company’s MPN structure (e.g., 62, Nr. 2, S. 629–652, 2013.
towards a digital one) is supervised and documented. Finally, the [18] B. Avak, „Variant management of modular product families in the
monetary aspects and the area of cost efficiency in general (e.g., market phase“, ETH Zurich, 2006.
calculation of the possible cost savings, if a certain MPN is
[19] Gartner IT Glossary, „Configure, Price, Quote (CPQ) Application
introduced), which were not considered in this publication, would
Suites“. 16-Apr-2018.
make a major contribution, especially for the practitioners.
[20] S. Tsukatani, T. Inokuchi, and H. Ito, „Multi-session disc-shaped for
recording audio and computer data having disc type code area located
REFERENCES in each session for recording common and particular disc type code“,
Juli-1998.
[1] S. J. Hu, X. Zhu, H. Wang, and Y. Koren, „Product variety and
[21] D. E. Denning and D. K. Branstad, „A taxonomy for key escrow
manufacturing complexity in assembly systems and supply chains“,
encryption systems“, Commun. ACM, Bd. 39, Nr. 3, S. 34–40, 1996.
CIRP Ann.-Manuf. Technol., Bd. 57, Nr. 1, S. 45–48, 2008.
[22] R. Elz, „Serial number arithmetic“, 1996.
[2] C. Huffman and B. E. Kahn, „Variety for sale: Mass customization or
[23] J. Schickler, „Parts search system“, Aug-2004.
mass confusion?“, J. Retail., Bd. 74, Nr. 4, S. 491–513, 1998.
[24] R. K. Yin, Case study research and applications: Design and methods.
[3] C. Y. Baldwin and K. B. Clark, Design Rules: The Power of
Sage publications, 2017.
Modularity Volume 1. Cambridge, MA, USA: MIT Press, 1999.
[25] B. J. Baars and N. M. Gage, Fundamentals of cognitive neuroscience:
[4] T. Blecker, N. Abdelkafi, B. Kaluza, G. Kreutler, „Mass customization
a beginner’s guide. Academic Press, 2013.
vs. complexity: a Gordian knot?", Munich Personal RePEc Archive,
[26] N. Cowan, „The magical number 4 in short-term memory: A
890-903, 2004.
reconsideration of mental storage capacity“, Behav. Brain Sci., Bd. 24,
[5] W. ElMaraghy, H. ElMaraghy, T. Tomiyama, and L. Monostori,
Nr. 1, S. 87–114, Feb. 2001.
„Complexity in engineering design and manufacturing“, CIRP Ann.,
[27] G. A. Miller, „The magical number seven, plus or minus two: Some
Bd. 61, Nr. 2, S. 793–814, 2012.
limits on our capacity for processing information.“, Psychol. Rev., Bd.
[6] C. Forza and F. Salvador, „Managing for variety in the order
63, Nr. 2, S. 81, 1956.
acquisition and fulfilment process: The contribution of product
[28] A. Baddeley, „Working memory: theories, models, and controversies“,
configuration systems“, Int. J. Prod. Econ., Bd. 76, Nr. 1, S. 87–98,
Annu. Rev. Psychol., Bd. 63, S. 1–29, 2012.
März 2002.
[29] Y. Dudai, „How big is human memory, or on being just useful
[7] P. Mishra and T. Chandra, „Mergers, Acquisitions and Firms
enough.“, Learn. Mem., Bd. 3, Nr. 5, S. 341–365, 1997.
Performance: Experience of Indian Pharmaceutical Industry“,
[30] J. R. Anderson, Cognitive psychology and its implications. Macmillan,
Eurasian J. Bus. Econ., Bd. 3, Nr. 5, S. 111–126, 2010.
2005.
[8] V. Venkatesh and F. D. Davis, „A theoretical extension of the
[31] T. P. McNamara, „Mental representations of spatial relations“, Cognit.
technology acceptance model: Four longitudinal field studies“, Manag.
Psychol., Bd. 18, Nr. 1, S. 87–121, 1986.
Sci., Bd. 46, Nr. 2, S. 186–204, 2000.
[32] A. M. Collins and M. R. Quillian, „Retrieval time from semantic
[9] F. Piller, M. Koch, K. Moeslein, and P. Schubert, „Managing high
memory“, J. Verbal Learn. Verbal Behav., Bd. 8, Nr. 2, S. 240–247,
variety: how to overcome the mass confusion phenomenon of customer
1969.
co-design“, in Proceedings of the Proc. 3rd Annual Conf. of the
[33] J. L. Voss, „Long-term associative memory capacity in man“, Psychon.
European Academy of Management (EURAM 2003), Milan, Italy,
Bull. Rev., Bd. 16, Nr. 6, S. 1076–1081, 2009.
2003.
[34] H.-E. Eriksson and M. Penker, „Business modeling with UML“, N. Y.,
[10] D. W. Hoffmann, Einführung in die Informations-und
S. 1–12, 2000.
Codierungstheorie. Springer, 2014.
[35] M. C. Paulk, The capability maturity model: Guidelines for improving
[11] W. Heise und P. Quattrocchi, Informations-und Codierungstheorie:
the software process. Addison-Wesley Professional, 1995.
mathematische Grundlagen der Daten-Kompression und-Sicherung in
diskreten Kommunikationssystemen. Springer-Verlag, 2013.
[12] F. Piller and C. Berger, „Customers as co-designers“, Manuf. Eng., Bd.
82, Nr. 4, S. 42–45, Aug. 2003.