=Paper=
{{Paper
|id=Vol-1216/paper1
|storemode=property
|title=Sustainability and Longevity: Two Sides of the Same Quality?
|pdfUrl=https://ceur-ws.org/Vol-1216/paper1.pdf
|volume=Vol-1216
|dblpUrl=https://dblp.org/rec/conf/re/Becker14
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==Sustainability and Longevity: Two Sides of the Same Quality?==
https://ceur-ws.org/Vol-1216/paper1.pdf
Sustainability and Longevity:
Two Sides of the Same Quality?
Christoph Becker
Faculty of Information
University of Toronto
Ontario, Canada
Email: christoph.becker@utoronto.ca
Abstract—This paper attempts to shed light on the relation- Software aging has been one of the first terms used to de-
ships between the concerns of sustainability and longevity in scribe one aspect of this phenomenon, the perceived brevity of
software and requirements engineering. Disciplines related to useful system lifespans. In the last decade, increasing attention
longevity of information and of systems can bring interesting
ideas and perspectives to the discussion of sustainability. At the has been paid to the lack of longevity of the information assets,
same time, sustainability clearly is a crucial component and and the emerging fields of digital preservation and digital
critical success factor in determining an actual system’s longevity. curation focus on the set of processes necessary to sustain
While many isolated techniques exist, the various definitions digital information across social and technical boundaries.
of sustainability are not all aligned, and clarity on the concepts These fields have increasingly moved from focusing on the
is needed to move forward. We argue that it is crucial to
consider sustainability not just in the sense of lean software, digital information objects to a broader systems perspective.
green computing and functional requirements for improving In Software Engineering, sustainability is a comparably new
environmental sustainability, but also consider how it applies to topic with several connotations [6]. On one side it relates to en-
the systems under design in a holistic perspective. We discuss vironmental sustainability with a focus on environmental infor-
possible relationships and synergies and outline a set of research matics, green computing, and systems to support sustainability
questions for sustainability as a design concern.
in the environment. On the other side it relates to sustainable
I. I NTRODUCTION systems design. Here, the perspective has focused on software
The lack of long-term thinking in software and systems architecture and systems evolution (see for example [7]).
design has been a concern for at least two decades, since Disciplines such as preservation and curation provide in-
Parnas lamented the costs of aging software [1]. However, teresting angles of thought, experiences, and perspectives on
it is recently coming into increased focus from different sustainability, since they are by their nature taking a long-term
angles [2]. The trade-off between short-term interest and long- perspective. These fields have started to conceptualize and
term benefits manifests in a lack of sustainability with a variety articulate changes needed in software engineering to improve
of different symptoms and names - software aging [1], the the sustainability of information and computation ecosystems.
digital dark ages [3], technical debt [4], lifecycle costs, but also Their arguments mirror recent complaints about the lack of
negative impact on the environment of the system under design long-term thinking in software engineering [2].
or outside the (budget planning) time horizon. The latter is the This article tries to connect the dots in an attempt to
core aspect of what we commonly understand as sustainability: identify synergies and possible paths forward. The purpose
meeting ‘the needs of the present without compromising the is to contribute to the emerging discussion on sustainability in
ability of future generations to satisfy their own needs’ [5]. requirements engineering and systems design with a perspec-
Neumann emphasizes that ‘there is much to be gained tive on long-term sustainability of systems that is informed by
from farsighted thinking that also enables short-term achieve- a closely related domain that sustainability research has not
ments.’ [2]. However, in practice, aspects concerning end- yet been connected to.
of-lifecycle aspects, system durability, information security • We emphasize the similarities between conceptions of
and sustainability are often considered as an afterthought longevity and sustainability in recent literature, and clar-
or a low-priority requirement that can be sacrificed in the ify the distinctive relationships between the two.
heat of the race towards deadlines. This leads not only to • We shed some light on the sustainability of systems from
cost overruns and high lifecycle costs in software, but also a long-term information perspective.
manifests itself in systems that have negative impacts on their • We highlight the crucial nature of early-phase under-
environment, be it in the social dimension (such as security standing of such concerns and the role of requirements
flaws and privacy breaches), in the environmental dimension engineering in longevity and sustainability; and
(such as high energy and other resource consumption) or in • we pose a set of research questions that should contribute
the technical dimension, where this often becomes manifest to the larger picture of sustainability research in require-
as a lack of resilience, adaptability, durability, longevity, or ments engineering and information systems design.
system sustainability. In doing so, we will focus for the most part on the
sustainability of software and information systems, but also Recently, the question has been raised whether obsolescence
emphasize how this is closely related to the ‘other side’ is a real threat in an increasingly networked ecosystem [14].
of sustainability, the outward view of a system’s impact on There is no conclusive evidence [15], [16], and a better
the environment, and that these facets can be successfully understanding of the ecosystem is needed.
considered only in conjunction.
B. Sustainable infrastructure
The article is structured as follows. The next section will
introduce notions of information longevity and information From their origins in cultural heritage and eScience – in
systems longevity and discuss sustainability in digital curation particular archives, museums and libraries and the space data
and preservation. Section III discusses the implications of such and high energy physics domains – the concerns of digital
sustainability perspectives on requirements engineering, and longevity have become a major topic in fields ranging from
Section IV attempts to bring these perspectives together and eGovernment [17], [18] to digital libraries2 [19] or environ-
outline possible avenues of research and practice that appear mental sciences [20], [21].
promising. A particularly interesting application domain in this context
is the one of digital scholarship, research infrastructures, and
II. S USTAINABILITY OR LONGEVITY ? data science. This emerging ‘fourth paradigm’ of science
The perspective of this article is influenced by a field as ‘data-intensive scientific discovery’ [21] holds tremendous
whose very existence is built on the premise of sustainability: promises, most visibly maybe in the environmental sciences
Digital curation and preservation emerged as disciplines to where long-running data collections hold explanations for how
address the need to carry digital information into the future the human presence impacts life on our planet, and what can
in authentic form, in reliable and trustworthy environments, still be done to avoid the worst [22]. From a number of core
to be accessible and understandable for a community of users disciplines that have embraced this paradigm more openly than
- which is sometimes very narrow, but often as broad as the others, the word of open data and data sharing is spreading
general public [8], [9]. Hence, their focus by definition is on rapidly, as evidenced by the recent success of the Research
future rather than present needs. Data Alliance3 and its manifold interest and working groups.
The next sections thus introduce key aspects of these The sustainability of the emerging global research infras-
domains with a focus on sustainability. tructures, which are as much social infrastructures as tech-
nical ones, should be a key concern. Speaking about the
A. Information Longevity and Sustainability socio-technical nature of cyberinfrastructure, Edwards et al.
The emergence of digital curation and preservation as fields argue that one cannot design such infrastructure top-down,
was initially motivated by cases of information loss including that it grows in a bottom-up process instead. As such, the
satellite and census data stored on tapes [10] and expensive sustainability of dynamic ecosystems is a complex subject that
recovery projects such as the BBC Domesday disc [11]. As may elude intentional design to some degree: ‘Better, then, to
interdisciplinary fields, they are connected to digital archiving deploy a vocabulary of growing, fostering, or encouraging in
and records management, research data mangement, computer the evolutionary sense when analyzing cyberinfrastructure’ (
science and software engineering, information and knowledge [23], p.12). These thoughts certainly have relevance when con-
management, and digital libraries, to name a few. sidering external sustainability as a design goal for systems.
Graduating from preserving static bits of data stored on C. Economically sustainable information
media to preserving the dynamic processes that provide mean- The discourse surrounding digital preservation and curation
ingful information and interaction, the emerging conception of has increasingly moved from an ex-post treatment to empha-
digital preservation as enabling computation [12], in particular sizing the fundamental importance of sustainability both on
across ecosystem boundaries, puts the notion of sustainability the levels of infrastructure, organizations, and ecosystems [24]
center stage. In that, it concurs with the notion of sustainable and on the levels of software systems [12].
software as being designed to be ‘long-lasting’1 . The notion of An influential report on sustainable digital information [24]
‘long’ is necessarily a relative one and can last from 7 years (a analyzed the specific nature of digital information assets from
typical time horizon in legal compliance) to 5000 or more (a an economic perspective and highlighted structural challenges.
nuclear waste information management time horizon). In the The authors point to a number of phenomena of wider rele-
standard reference model for long-term digital preservation, vance to the sustainability perspective, including the following.
long-term is defined as ‘long enough to be concerned with the
• Misalignment of demand is a particular concern in
impacts of changing technologies ... or with a changing user
a field whose existence is derived from future demand
community.’ [13].
for access. Without preservation, there is no access; but
Research and practice in digital longevity has initially
without access, there is no need for preservation. Since
focused on mitigation actions, techniques, and controls to
most of the need occurs outside of most organization’s
address technological and socio-economic change and discon-
tinuity, in particular the perceived threat of obsolescence [8]. 2 Ross and Hedstrom explicitly use the term sustainability, although they
do not define it.
1 https://sustainability.wiki.tum.de/Sustainable+Software 3 https://rd-alliance.org/node
planning horizon, there is little incentive for investment; note the usage of the term preservation for defining sustainabil-
and it is often difficult, if not impossible, to calculate the ity. However, the question arises if sustainability requires the
net present value of digital assets. Whereas for digital exact notion of preservation – if a system evolves continuously
curation and preservation, the primary separator is time, to better provide its function and values to the environment
for other areas it is social structure that separates sustain- without negative impact, that seems to be a very sustainable
ability stakeholders from system designers and decision system without necessarily preserving its function in full.
makers. On the other hand, it seems that the narrow interpretation of
• Market failure is a common effect of this misalignment: technical sustainability in [25] misses the wider social ecosys-
It often makes no economical sense for agents to engage tem facet of system sustainability, where technical system
in sustainable activities, since their short-term interests qualities can only be seen as co-determinants of sustainability.
outweigh possible long-term benefits given their business The exit point addressed above corresponds to what Milic-
drivers and the market structures they operate in. Frayling calls the explicit consideration of end-of-life aspects
• Incentives and mechanisms. Taking a broader perspec- of system design: Besides established software quality at-
tive on sustainable information ecosystems, the report tributes, ‘we need to include properties that pertain to the end-
raises the question whether one can ‘design institutions of-life of computing systems. These should include provisions
that create incentives for private individuals, acting in for minimizing the expected effort and cost of sustaining
their own interests, to make choices and take actions digital assets produced by the system.’ [12].
that achieve the desired public purpose’. ( [24], p. 94)
It identifies a need for research into how mechanism E. Synthesis
design approaches employing game-theoretic concepts
can provide a deeper understanding of the subject. So what can digital curation, archiving and preservation
– or digital stewardship, as it is sometimes called [33]–
D. Information Systems Longevity and Sustainability bring to the sustainability debate in requirements and software
Increasingly, the perspective of research on digital longevity engineering?
has shifted towards addressing the root causes and establish Since curation and preservation by their nature take a long-
longevity as a design concern upstream in the systems lifecy- term perspective, they can offer insights into the role that
cle. We articulated this explicitly in [25], where we observed the longevity of information assets play in the sustainability
that many approaches and techniques exist in isolated per- and longevity of the system which they are part of. As
spectives that contribute to increase both information longevity such, advocates of sustainability in software and requirements
and system longevity (and sustainability), but that there are no engineering can find a natural ally in the domains of digital
accepted perspectives on longevity as an overarching concern curation and preservation.
that would integrate and drive such techniques. We argued for We noted that the conceptualizations of sustainability in
interdisciplinary research efforts dedicated towards long-term software and requirements engineering are very similar in
perspectives on systems design from the inception onwards. In nature to the conceptualization of longevity as outlined above.
the conception of longevity as an information systems design If sustainability is defined as ‘preserving the function of a
concern brought forward in [25], longevity as a systems design system over a defined time span’ [27], is there a difference
concern is composed of three major concerns. at all between longevity, preservation, and sustainability of an
• Information longevity relates to the ”ability to govern information system?
information independently of and across systems”. For one, preservation may not be an adequate term to define
• The ”ability to sustain the information system, across an sustainability, as it implies fixing an entity over time, whereas
unstable organizational and technological context, for as sustainability is a more open-ended and relational concept
long as a defined set of conditions holds” is further linked that refers to how systems influence each other. Longevity
to the qualities of system evolution and system resilience as an effect manifests only in time. As a design concern, it
as key quality concerns. emphasizes the durability of the system itself and the crucial
• Finally, the existence of an exit point enables the system importance of thinking beyond that duration, recognizing the
owner to ”move the information base and the defined importance of external relationships. Sustainability is by nature
valid state changes.... to .. another system” when this is of its origin concerned with contextual factors, but emphasizes
beneficial. [25] the long-term aspects this perspective entails. The observed
We note that these observations and arguments show striking effect of long-living systems that have no negative impact on
parallels to those voiced by [26], [27] from the perspective of the environment is similar for both perspectives.
software engineering for sustainability: The notion of sustain- Long-term sustainability of information about a system is
ability corresponds to relative sustainability defined in [27] – fundamental for understanding the sustainability of the system
the expectation that the organization context surrounding the itself. The fundamental importance of designing sustainability
solution space artifacts will be able to sustain the system for into the infrastructure, organizations, and systems for digital
as long as needed, ‘preserving the function of a system over a curation and preservation makes these fields an interesting test
defined time span’ [27]. It is in this context very interesting to case for approaches to sustainability.
It becomes clear that it would be counterproductive to focus Assessing the real gaps of engineering techniques in the
definitions of sustainability on the external view alone, i.e. light of sustainability requirements requires a solid understand-
the absence of negative impact on the environment. A holistic ing of sustainability concerns. This needs to build on solid con-
perspective including both sides of the coin, as suggested for ceptual foundations. Future studies need to go beyond claiming
example by [27], is much more representative of the very that sustainability is a relevant quality and clearly translate the
nature of sustainability itself. concern in specific instances into relevant qualities to enable
designers to address these concerns systematically. Initial
III. I MPLICATIONS FOR SUSTAINABILITY IN studies such as by Mahaux [31] demonstrated the feasibility
REQUIREMENTS RESEARCH
of addressing concrete sustainability concerns with existing
There is ample awareness of the need to address sustainabil- requirements concepts and techniques. Penzenstadler argued
ity in academic literature, as evidenced recently for example in that models from the sustainability domain can provide useful
Special Issues of IEEE Software on Architecture Sustainability assistance in requirements engineering activities [32]. Larger
and on Green Software. However, this does not translate efforts and a shared knowledge base are needed to establish
into practical success. As Neumann points out, ‘We should common terminology, identify patterns, and deepen the un-
anticipate the long-term needs that a system or network of derstanding of the complex relationships between the design
systems must satisfy, and plan the development to overcome concerns, stakeholders, system capabilities and qualities, and
potential obstacles that might arise, even if the initial focus possible patterns of addressing them.
is on only short-term needs. This might seem to be common
IV. C ONCLUSION AND O UTLOOK
wisdom, but is in reality quite rare. Common requirements
for ... adaptability, human safety, interoperability, long-term A. Summary
evolvability, trustworthiness, and assurance evaluations are We have attempted to highlight new relationships between
generally much too weak.’ [2] Why is this the case? digital longevity and sustainability, illustrating the relevance
A crucial distinction has to be made between a solution- of sustainability in disciplines such as digital curation and
oriented system quality and a (problem-oriented) concern, preservation and highlighting approaches to sustainability in
i.e. an ‘interest in a system relevant to one or more of its these disciplines.
stakeholders’ [28]. The latter does not simply translate into the It becomes clear that it is crucial to apply sustainability not
former. For example, the sustainability of a system architecture just in the sense of lean software and functional requirements
as defined by Koziolek et al [29], [30], is clearly a system to support sustainability outside the system, but also consider
quality. However, sustainability of a complex socio-technical how it applies to the systems under design. Not only are these
information system does not translate into a system quality the aspects that are under the control of the designer, they are
easily. Similar to the notion of IS longevity outlined in [25], it also the opportunity to turn concepts onto our own field and
is a design concern that will be relevant to certain stakeholders, evaluate the contributions first-hand. Promising approaches
not all of which are commonly involved directly in the have been brought forward, but a common understanding is
requirements and design stages. It will raise the importance of lacking, and a certain incoherence can be diagnosed between
specific capabilities and qualities in the system under design related, non-competing approaches with potential for synergy.
and will need to be addressed using specific viewpoints, This is of course a normal observation for an emerging field.
methods, concepts and techniques.
It is this observation that emphasizes the crucial role of B. Research questions
requirements engineering in sustainability: For the most part, In the following, we outline some questions that arise from
some techniques required to address sustainability may already the discourse. Instead of providing a comprehensive roadmap,
exist. They include patterns that increase architecture modular- this should be seens as a starting point for a broader discussion
ity and hence facilitate evolution, model-driven approaches to and engagement.
decouple long-living conceptual aspects from short-lived tech- • Trade-off decisions. The different dimensions of sustain-
nical implementation aspects, trade-off analysis methods, and ability (social, technical, human, and environmental) are
many others. By identifying relevant aspects and facilitating interrelated. Real sustainability is only achieved where
prioritization, requirements engineering can bring into focus all areas overlap. This implies that over-investing to
those elements that are most critical; identify stakeholders and extend one aspect of sustainability will be wasteful unless
concerns and their relationships; establish which trade offs excess sustainability from this or another dimension can
have to be considered; and thus ensure a focus on critical be transferred to cover gaps in other dimensions. A
aspects with a real impact on sustainability in specific system typical case is a transfer of economic excess sustainability
scenarios. towards technical sustainability, investing into a software
However, for many systems, the concerns are not sufficiently architecture renovation in order to address technical debt.
identified as relevant and valuable, the implications are not Can early-phase models support robust design decisions
well understood, and the techniques hence often not applied. considering these trade-offs?
Evidence on the effectiveness of these techniques over longer • Digital ecosystems. The focus on early phases and the
timespans is scarce. contextual understanding of a system requires a much
more profound understanding of ecological questions in enabling practitioners to introduce these concepts to their
dynamic ecosystems. For example, how do the life cycles clients. First efforts have started to address this, but
of adjacent and indirectly connected systems and tech- are limited to environmental sustainability features and
nology components affect the sustainability of a system not based on rigorous analysis [38]. Correspondingly,
under design? How do the lifecycles of digital ecosystems design patterns for particular solution schemes in well-
affect their environment? contextualized situations will be a natural future step to
• The role of information longevity and curation. In enable broader takeup of tested solutions. Such patterns
addition to system qualities, the question arises what could likely be identified already in the domains of
role information longevity plays in supporting system preservation and curation.
sustainability, and how this goes beyond what is currently • Practice. As pointed out 15 years ago in a related context,
recognized as data quality in ISO SQUARE [34], [35]. ‘”The real problem”, says computer designer Hillis, ”is
• The impact of long-term preservation. Not only do not technological. We have the technical understanding
many digital objects live much longer than originally to solve problems such as digital degradation. What we
intended today - and in multiple redundant locations - we don’t have yet in our digital culture is the habit of
also do not normally know the potential negative impact long-term thinking that supports preservation...”’ [3] If
of creating or preserving them. It has been possible to that is the case regarding sustainability, what are the
provide an estimate of the carbon footprint of a Google inhibitors that prevent the concern from being succes-
search, but it is much more difficult to provide an estimate fully addressed, and how can requirements engineering
for the footprint of a new piece of digital data to be stored contribute to an increased awareness of the importance
for 10 years or more. and benefits of this concern?
• Modelling. Sustainability clearly calls for holistic per- • Culture. System designers often lack an understanding
spectives. Lankhorst points out the shortage of support for of the cultural and social determinants of sustainability
assessing longer-term change in system architectures be- on organizational, societal, and community levels. A
forehand [36]. Can Enterprise Architecture be leveraged shared understanding of key factors should provide a
effectively for addressing sustainability concerns? Does a useful toolset for requirements analysis. This could first
successful consideration of sustainability in software and on specific highly interested communities such as green
systems design require new viewpoints? computing, research infrastructures, or digital curation.
Recent contributions discussed the sustainability of archi- What are the cultural factors that influence the perception
tectural design decisions [37] and emphasized the role of of relevance of sustainability in organizations? Can a
decision viewpoints to support architectural design [7]. systematic approach towards analyzing and documenting
Do current viewpoints provide adequate support for de- these in an RE process increase the effective considera-
cision making in sustainability? How can requirements tion of sustainability concerns?
engineering support a systematic and traceable consider-
C. A sustainable software design manifesto?
ation of sustainability aspects in architectural design?
• Qualities. How do inwards and outwards sustainability
Neumann, a vocal advocate for long-term thinking, calls
relate to system qualities? How can these relationships for more systematic experimentation and more formality in
be analyzed systematically? While the contribution of design, but also emphasizes the importance of a ‘holistic
performance efficiency to green computing is one obvious balance of human intelligence, experience, memory, ingenuity,
answer, it is clearly not the only connection that can creativity, and collective wisdom, with slow and fast thinking’
be made. When considering longer timeframes, the rela- [2], pointing to Kahnemann [39].
tionships become more complex. We need a much more To facilitate the establishment of a stable and sustainable re-
precise understanding of the relationships between both search agenda, a focal point of reference is needed, synthesiz-
types of sustainability and specific software capabilities ing the diverse aspects and providing an openly accessible, ro-
and qualities, underpinned by empirical studies. bust and clearly delineated reference point clarifying the scope,
Generally, quality is used in a static sense, missing a facets, objectives and challenges of the emerging research
designation of its evolution over the system lifetime. discipline and enabling the setup of interdisciplinary platforms
However, the desired system qualities will inevitably of research and practice. It may be the right moment for a
change over time. How can we anticipate likely changes sustainable design manifesto for requirements engineering (or
with critical impact early? software engineering) as a focal point bundling objectives and
• End-of-life. Under which circumstances should end-of-
perspectives in a coherent message of reference.
life concerns be considered? Can there be a case made for Analogous examples to consider are plentiful, in particular
these that is convincing to decision makers and system in the general area of sustainable design4 , but generally aimed
designers in the initial stages of the system lifecycle? at a non-academic, broad audience. On the software side, they
• Requirements patterns for specific sustainability con-
include the Agile Manifesto5 and the Business Rules mani-
texts and concerns could provide a helpful resource 4 e.g. http://www.core77.com/reactor/04.07 chochinov.asp
for the broader community of requirements engineers, 5 http://agilemanifesto.org/
festo6 , but also the SOA manifesto7 and the Recomputation [15] D. Pearson and C. Webb, “Defining file format obsolescence: A risky
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ACKNOWLEDGMENT “Climate change 2014: Mitigation of climate change,” 2014.
[23] P. Edwards, S. Jackson, G. Bowker, and C. Knobel, Understanding
Part of this work was supported by the Vienna Science and Infrastructure: Dynamics, Tensions, and Design, Report of a Workshop
Technology Fund (WWTF) through the project BenchmarkDP on History & Theory of Infrastructure: Lessons for New Scientific
(ICT12-046). The author would like to thank Birgit Penzen- Cyberinfrastructures, 2007.
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