Aili Biriita Bertnum
email: aili.b.bertnum@ntnu.no

Marco Semini
email: marco.semini@ntnu.no

Jan Ola Strandhagen
email: ola.strandhagen@ntnu.no

Planning environments of hospital laboratories: An exploratory study

Keywords: Planning Environment, Service Operations, Hospital Laboratories

Hospital laboratories are facing challenges of increasing demand and limited budgets. Planning and control can improve resource utilization, reduce work-in-progress and shorten throughput times, but to achieve such benefits, there is a need for a strategic fit between the planning and control system and the unique planning environment of the hospital laboratory. Existing research on planning environments focuses mainly on manufacturing companies, whereas hospital laboratory planning environment research is scarce. The aim of the study is to characterize a hospital laboratory's planning environment based on an exploratory case study. The findings indicate an overall strategic fit of the case laboratory's planning environment, but a lack of strategic fit between large batch sizes and low set-up times. Hospital laboratory planning environment research must be further developed through multiple case studies, as hospital laboratories are different in service provision and organizational structure. This study increases knowledge on planning environments in hospital laboratories, and suggests topics for future research.

Introduction

Test results from hospital laboratories are a vital support for physicians in decision making regarding a patient's health. Thus, hospital laboratory throughput time, also called turnaround time, is crucial to prevent delays in patient treatment [START_REF] Dolci | Total laboratory automation: Do stat tests still matter?[END_REF]. With continuously increasing demand and limited budgets, hospital laboratories are facing a challenging future. They need to improve utilization of existing resources, while at the same time reduce work-in-progress and shorten throughput times. An appropriate planning and control system can support these objectives, but it requires the planning and control system to be aligned with the characteristics of the planning environment [START_REF] Berry | Linking systems to strategy[END_REF].

A lack of such a strategic fit will negatively affect performance [START_REF] Berry | Linking systems to strategy[END_REF].

Planning environments are company-specific, and its characterizing variables are typically related to the product, market and manufacturing of the specific company [START_REF] Hayes | Restoring our Competitive Edge: Competing Through Manufacturing[END_REF][START_REF] Jonsson | The implications of fit between planning environments and manufacturing planning and control methods[END_REF][START_REF] Buer | Strategic Fit of Planning Environments: Towards an Integrated Framework[END_REF]. Most research related to planning environment and strategic fit takes a manufacturing point-of-view. Planning environment research in hospital laboratories, however, is scarce. The aim of the study is, therefore, to characterize the planning environment of a hospital laboratory, which provides a starting point for the generation of knowledge on how to plan and control hospital laboratories.

A single and exploratory case study of a hospital laboratory department at a Scandinavian hospital was performed to achieve an in-depth understanding of its planning environment. The control model methodology has been used as a systematic approach to visualize and analyze the hospital laboratory's current production and logistics system [START_REF] Strandhagen | A Manufacturing Business Process Reengineering Method: Design and Redesign of a Production Control Model[END_REF]. Furthermore, Buer et al. [START_REF] Buer | Strategic Fit of Planning Environments: Towards an Integrated Framework[END_REF] compiled existing manufacturing planning environment research into a framework for mapping planning environments, which has been used in this study to map the planning environment of the hospital laboratory.

The paper has the following structure. In section 2, relevant literature on planning environments is reviewed and common hospital laboratory planning and control challenges are introduced. In section 3, the hospital laboratory is described by the control model methodology and Buer et al. [START_REF] Buer | Strategic Fit of Planning Environments: Towards an Integrated Framework[END_REF]'s planning environment mapping framework. The planning environment's strategic fit and its planning and control challenges is discussed in Section 4. The paper ends with suggestions for future research in Section 5.

Planning environments

Numerous authors have investigated manufacturing planning environment variables and categorizations. Hayes and Wheelwright [START_REF] Hayes | Restoring our Competitive Edge: Competing Through Manufacturing[END_REF] developed the product-process matrix, which is probably one of the most recognized frameworks for choosing manufacturing processes based on product and market characteristics. Manufacturing planning environment research is often based on the customer order decoupling point (CODP). E.g., Jonsson and Mattsson [START_REF] Jonsson | The implications of fit between planning environments and manufacturing planning and control methods[END_REF]'s four generic planning environments categorizations and Stavrulaki and Davis [START_REF] Stavrulaki | Aligning products with supply chain processes and strategy[END_REF]'s further development of the product-process matrix, were based on the well-known CODPs: engineer to order (ETO), make to order (MTO), assemble to order (ATO) and make to stock (MTS). Buer et al. [START_REF] Buer | Strategic Fit of Planning Environments: Towards an Integrated Framework[END_REF] identified 30 planning environment variables from relevant literature and developed a framework for mapping planning environments in manufacturing companies. In the framework, the variables are grouped into three categories: product, market and manufacturing. Ranges of values are defined to each variable, which are sorted based on the CODPs. The framework reveals the company profiling, which can be used to assess the strategic fit of the product, market and manufacturing variables, where a lack of strategic fit provides the basis to evaluate planning and control related changes.

The different functions in healthcare systems, such as hospital laboratories, provide various healthcare services. To the best of our knowledge, there exists no planning environment framework from a service operations-perspective, such as Buer et al. [START_REF] Buer | Strategic Fit of Planning Environments: Towards an Integrated Framework[END_REF]. However, Wikner et al. [START_REF] Wikner | Decoupling thinking in service operations: a case in healthcare delivery system design[END_REF] introduced two additional service operations decoupling points. The customer adaptation decoupling point (CADP) marks where the service is adapted to a specific customer. The customer contact decoupling point (CCDP) refers to the type of customer contact, either front-office, back-office or a combination.

Nguyen et al. [START_REF] Nguyen | Hospital Planning Environment Variables Applied in Practice: A Multiple Danish Case Study[END_REF] mapped the planning environment of three outpatient departments in Danish hospitals, revealing large differences in patient requirements, patient flow and resource availability. While hospital laboratories have no patient contact, they are, like outpatient departments, highly different in service provision and organizational structure. Laboratories can be centralized with the ability to analyze all incoming samples, or decentralized where each unit is responsible for a specific analysis field [START_REF] Dolci | Total laboratory automation: Do stat tests still matter?[END_REF]. E.g., microbiological laboratories identify microscopic organisms in biological samples, whereas pharmacological laboratories detect the share of drugs and medicine.

Several planning and control challenges are present in hospital laboratories. An unbalanced workload is common due to the unpredictable nature of accidents and illnesses, which makes it challenging to balance demand and supply [START_REF] Leeftink | Predicting turnaround time reductions of the diagnostic track in the histopathology laboratory using mathematical modelling[END_REF]. Batch-based processing is also common in hospital laboratories, due to large material costs, among other. Large batches often cause prolonged processing times, and may lead to a specific operation only being performed once a day. Thus, samples coming in after the operation has been run, would have to wait until the next day to be processed [START_REF] Hewer | Implementation of a 'lean'cytopathology service: towards routine same-day reporting[END_REF]. In addition, machine-based operations with long durations are often being run during the night, which causes a one-day delay for all test results [START_REF] Leeftink | Batch scheduling in the histopathology laboratory[END_REF].

Case study

The case study involves a pharmacological laboratory department at a large Scandinavian hospital, offering analyses of the share of drugs, medicine and other substances in biological samples, such as blood and urine. Emergency preparedness around the clock for samples requiring immediate analysis is also offered, but is usually a negligible disruption due to its low occurrence. The product, market and customers of the case laboratory are described in section 3.1. The production processes and logistics are described in section 3.2, and visualized as an AS-IS control model in Fig. 1.

Product, markets and customers

The case laboratory delivers test results, which contains verified and interpreted information from the analysis of the biological sample. Test results are often used to detect drug and alcohol misuse, or to assess the effect of a medicine in patient treatment. The laboratory is able to analyze almost 300 substances. Several substances can be analyzed by one analysis method, and will be further described in section 3.2. Approximately 200 000 biological samples are delivered to the case laboratory on a yearly basis. More than 40% of the demand concerns drug analysis, which is usually performed in urine samples because of its longer drug tracking time, compared to blood samples. Analysis of Vitamin D and medicine make up approximately 25% and 20% of the demand, respectively. These analyses are usually done in blood and serum samples for higher accuracies of substance share. The remaining 15% of demand concern many specialized and low demand substances, including forensic examinations with higher requirements to quality and traceability.

Seasonal variations are observed, such as an increase in demand in advance of public holidays. In addition, weekly variations in incoming samples are common due to the postal service operating from Monday to Friday. This results in least incoming samples on Monday and most incoming samples on Tuesday. However, the seasonal and weekly variations do not impose a need for extra capacity.

The customers are the health professionals requesting the analysis of one or several substances, and supplying the biological sample. The patient, on the other hand, is both the end customer and the provider of this raw material. There are three main customer types: health professionals from the hospital itself, local healthcare institutions and regional healthcare institutions. They are differentiated by geographical distance, sample transportation mean and ordering system, and will be further described in section 3.2.

Production and logistics

The production and logistics activities are visualized in Fig. 1, and are further described.

Hospital orderlies collect and deliver samples from the hospital and local healthcare institutions twice a day. Samples from regional healthcare institutions are delivered daily by mail due to the geographical distance, which prolongs delivery time with 1-3 days. In the receive process, samples are coupled with the corresponding order. It defines the case laboratory's CODP, best characterized as ATO as chemicals are readymixed, but the analysis is postponed until a sample with an order is in place. Paperbased orders from local and regional healthcare institutions are delivered with the samples, and are manually registered into the laboratory information system (LIS). Electronic orders from the hospital and a few local healthcare institutions are collected from the shared information system (XIS). Samples coming from the hospital are ready-registered, while other samples are manually registered into LIS. Adaptations to customer orders happen already in the registration process and presents the CADP. to the limited sample shelf life. E.g., some samples need to be frozen to prevent the substance from evaporating. Thereafter, the samples are prepared, entailing small operations, such as moving the biological material into the correct tube when delivered in the wrong tube, dividing the biological material into several tubes when several analysis methods are required, and centrifuging blood into serum. The samples are then processed into analyzable tests, entailing pipetting, evaporation, dissolving, adding chemicals, heat-treating, or a combination, specified by the analysis method. Processing takes place in various manual-labored workstations, and semi-automated machines and robots, which require manual sample transportation as well as manual machine refill. The analyzable tests are pipetted onto plates and placed into the analysis machines. The samples are stored for a given period in case there is a need to redo the analysis. The analysis machines are programmed based on the analysis plan at the end of the workday. It takes 5 minutes to analyze a single sample, and the analysis time increases correspondingly with the batch size. The next morning, the analysis machines are emptied and cleaned. Bioengineers verify the analysis by checking if the test results are within the reference values. A doctor is responsible for interpreting the results, and can also give advices regarding adjustments to or change of medicine. Then, the test result is sent to the customer, either electronically through XIS, or paper-based by mail. The CCDP constitute a mix of front-office activities, e.g., test result reporting and consultation, and back-office activities, e.g. procuring materials and preparing for analysis.

The customers place orders based on the cyclic master schedule, which states the analysis methods to be run on a given day. This schedule is based on factors such as historical demand, test result urgency and samples' shelf lives. Around 60 analysis methods are run on a regular basis. Low demand and medium demand analyses are run twice a month and twice a week, respectively, in batches of 10 to 20 samples, and high demand analyses are run daily in 2-3 batches of 100 samples. The workday starts with making a daily analysis plan stating the final schedule of analysis methods. Analyses should be performed to schedule, as test results are used in patient treatment. Yet, for cost reduction reasons, postponement is considered when the batch size requirement for running the analysis is not met, given that the samples' shelf lives allow for it. Analyses can also be run earlier than scheduled if the batch size requirement is met, or if there is a need for a faster delivery of the test result.

Inventory levels of consumables and equipment are manually checked once a week. The order frequency is controlled by a reorder point and order-up-to system, given the demand, delivery lead-time and storage capacity of each item. Consumables and equipment constitute 50% of the total material supply, delivered from the hospital's central warehouse with a lead-time of 1-3 days. Chemicals constitute the other half of material supply, and are controlled by an automatic stock replenishment system tracking the actual usage of each chemical. Chemicals are delivered from chemical suppliers all over the world, with a lead-time of 3-10 days. High consumption materials have deliveries weekly, e.g. disposable gloves, pipettes and certain gas types. Materials with a very low consumption, such as machine parts can be ordered as seldom as every second year.

The summary of the product, market and manufacturing variables of the case laboratory's planning environment is provided in Table 1. The planning environment is characterized based on Buer et al. [START_REF] Buer | Strategic Fit of Planning Environments: Towards an Integrated Framework[END_REF]'s mapping framework for manufacturing companies.

Discussion

The planning environment of companies often falls rather homogeneously within one of the four CODPs, which indicates a strategic fit between product, market, and manufacturing variables [START_REF] Buer | Strategic Fit of Planning Environments: Towards an Integrated Framework[END_REF]. The case laboratory resembles manufacturing companies, with functional entities performing specific tasks that combined make up the final product.

Its planning environment has many values within ATO, the case laboratory's CODP, and MTS (see Table 1), indicating an overall strategic fit. However, some variables deviate as well, which can have a negative effect on performance [START_REF] Dolci | Total laboratory automation: Do stat tests still matter?[END_REF]. E.g., low set-up times and high capacity flexibility are usually associated with ETO or MTO companies. The case study is in agreement with the literature inasmuch as unpredictable demand and unbalanced workload present hospital laboratory-related planning and control challenges. The case study further points out large varieties of both incoming raw materials and analysis methods, as well as limited sample shelf lives. However, a mismatch is identified between the case study's batch sizes and batch-based part flow on one hand, and low set-up times and high capacity flexibility on the other hand (see Table 1). Large batch sizes give longer processing times, which is especially true for the analysis process in the case study. A single sample takes 5 minutes to analyze, whereas a batch of 100 samples will correspondingly take more than 8 hours to analyze. Nighttime analysis itself delays the test result delivery with one day [START_REF] Leeftink | Batch scheduling in the histopathology laboratory[END_REF].

According to a recent study of a hospital laboratory, reducing nighttime analysis, balancing the workload, and increasing the number of batches can result in a 20% reduction of throughput time [START_REF] Leeftink | Batch scheduling in the histopathology laboratory[END_REF]. It is also found that increasing the frequency of operations, even from once to twice a day, can largely reduce throughput times [START_REF] Hewer | Implementation of a 'lean'cytopathology service: towards routine same-day reporting[END_REF]. The case laboratory runs large batch sizes due to high fixed batch-related costs, such as expensive materials. However, the low set-up times should make it possible to reduce the batch sizes, as well as increase the number of batches and analysis frequency. It will result in a more balanced workload, and have a large impact on the case laboratory's throughput time and performance.

Conclusion

Planning and control can improve resource utilization, reduce work-in-progress and shorten throughput times in hospital laboratories, but it is important to have a strategic fit with the planning environment. Existing research on hospital laboratory planning environment is scarce, and there exists no known service operations framework for mapping planning environments. Therefore, this study characterized a hospital laboratory's planning environment with a mapping framework for manufacturing companies.

The findings indicate an overall strategic fit of the case laboratory's planning environment, but a lack of strategic fit between large batch sizes and low set-up times. The low set-up times present an improvement possibility inasmuch as they allow processing in small batches.

A limitation of this study is the use of a single case, which makes it difficult to generalize the findings to other hospital laboratory types. We suggest executing multiple case studies to compare planning environments of different hospital laboratory types. This study also revealed a lack of a framework for mapping planning environments in service operations, which also presents a future research topic.

Fig. 1 .

 1 Fig. 1. AS-IS control model of the hospital laboratory department

Table 1 .

 1 The planning environment of the pharmacological laboratory department

		Variables			Values
		CODP	ETO	MTO	ATO	MTS
		Level of customi-zation	Fully customer specific	Allows some specifications	None
	Product	Product variety BOM complexity	High <5 levels	Medium 1-2 levels, 3-5 levels several items	Low 1-2 levels, few items
		Data accuracy	Low		Medium	High
		Level of process planning	None	Partial process plan-ning	Fully designed pro-cess
		P/D ratio	<1		1		>1
		Demand type	Customer order allo-cation	Calculated require-ments	Forecast
		Demand source	Customer order		Stock replenishment order
				Several cus-	Large number	Frequent call-
		Volume/fre-	Few large cus-	tomer orders	of customer or-	offs based on
		quency (per year)	tomer orders	with large	ders with me-	delivery sched-
	Market	Customer de-mand frequency	Unique	quantities Block-wise or sporadic	dium quantities Regular	ules Steady (continuous)
		Time distributed demand	Annual figure		Time distributed
		Demand charac-teristics	Dependent			Independent
		Type of procure-ment ordering	Order by order procurement	Order releases from a delivery agreement
		Inventory accur.	Low		Medium	High
		Mfg. mix	Mixed products		Homogenous products
		Shop floor layout Fixed-position	Functional	Cell	Product
		Production type	Single unit pro-duction	Small series	Serial production	Mass production
		Throughput time	Years	Months	Weeks	Days	Hours
		Major operations	High		Medium	Low
			Equal to cus-
		Batch size	tomer order
	Manufacturing		quantities

Small, equal to one week of demand Medium, equal to a few weeks of demand

						Large, equal to
						a month's de-
						mand or more
	Production order	Non-repetitive pro-	Production with in-	Production with fre-
	repetition freq.	duction		frequent repetition	quent repetition
	Fluctuations of capacity req.	High		Medium		Low
	Planning points	High		Medium	Low
	Set-up times	Low		Medium		High
	Sequencing de-pendency	None		Low	Medium	High
	Part flow	One-piece flow	Overlapped	Lot-wise	Bulk (batch)
	Material flow complexity	High		Medium	Low
	Capacity flex.	High		Medium		Low
	Load flexibility	High		Medium	Low

Acknowledgements. This research received funding from the strategic research area NTNU Health in 2020 at NTNU, Norwegian University of Science and Technology. We also want to acknowledge the case hospital laboratory taking part in this study.


Ali Gharaei

Jinzhi Lu
email: jinzhi.lu@epfl.ch

Oliver Stoll

Xiaochen Zheng

Dimitris Kiritsis

Systems Engineering Approach to Identify Requirements for Digital Twins Development

Keywords: Digital Twin, Systems Engineering, Architecture Design

Digital Twins (DT) are proposed in industries to support the entire lifecycle of services with different perspectives. Lack of systematic analysis of DT concepts leads to various definitions and services which challenges the DT developers for data integration and integrated service delivery. In this paper, a systems engineering approach is proposed to identify the requirements of DT in order to formalize the DT concepts from a systematic perspective. The conceptual architecture of DT is defined based on ISO standard 42010. Several concepts are captured to recognize DT, to define related terminologies, and to identity concerns and viewpoints in order to provide cues for delivering DT services to industry. This approach is evaluated by multiple industrial use-cases under the Innosuisse IMPULSE project, from which one-use case is selected for further elaboration. It contributes to the development of DT associated to the use-case by addressing the requirements of DT using a semi-formal approach.

Introduction

With the rapid advancement of Industry 4.0, Digital Twins (DT) are increasingly gaining attention for their potential to support intelligent decision-making for real-time cyber-physical systems. As an emergent technique, many industries from different domains are developing different DT concepts aimed at establishing cost-effective solutions for product development and maintenance. However, the DT concepts are separately defined by different domains, which leads to challenges defining a unified DT concept. Without unified definitions, stakeholders of DT find it difficult to communicate with the same language and thought structure. This negatively impacts the proper delivery of DT services and decision-making identifications.

The DT is a digital duplication of entities, with real-time two-way communication enabled between the cyber and physical spaces [START_REF] Lu | Cognitive Twins for Supporting Decision-Makings of Internet of Things Systems[END_REF]. As a DT is developed, four main perspectives need to be considered: i. DT domains; ii., DT organizations; iii., DT models; and, iv., DT decision-making. DT domains refers to the disciplines the DT is used for. DT organizations refer to the group and enterprises providing DT concepts. DT models refer to models constructing virtual entities of DT. DT decision-making to the purposes. These perspectives are difficult for DT stakeholders to identify because the systematic view of the DT requires more domain-specific knowledge. Thus, a general architecture description of DT is useful for stakeholders for DT development, implementation and maintenance.

The contribution of this paper is to illustrate a systems engineering approach to formalize architecture descriptions of DT for different domains. Based on ISO standard 42010 as a reference model, DT is defined as a "system" whose architectural entities are formalized including stakeholder concerns and viewpoints. Through these entities, requirements are identified which are used for making decisions about DT service delivery. Finally, an ontology model is developed to visualize the architectural entities from the selected use-case in an Innosuisse project IMPULSE, which aims to provide a unified architecture description of DT.

The rest of the paper is organized as follows. We discuss the related work in Section 2 and introduce the systems engineering approach to identify the architecture description of DT in Section 3. In Section 4, the use case is elaborated to evaluate the approach to identify each requirement of DT development. Finally, we discuss findings and offer our conclusions with a summary in Section 5.

Based on the output of this paper an ontology-based approach will be used as a continuation of this works to formalize the architecture entities of DT and visualize a DT concept. This, however, remains beyond the scope of this paper.

Literature review

The concept of digital twins is an emergent technique aiming at providing a rapid and effective solution for product development [START_REF] Bricogne | Design Processes of Mechatronic Systems[END_REF]. The DT concept consists of physical products in real space, virtual products in virtual space and communications between these two spaces [START_REF] Tao | Digital Twin in Industry: State-of-the-Art[END_REF]. Different domain specialists provide different definitions and technologies to construct digital twins [START_REF]INTERNATIONAL STANDARD ISO / IEC / IEEE Systems and software engineering -Architecture description[END_REF]. This brings a new challenge to define and formalize the architecture of DT so stakeholders can make appreciate decisions when developing DT [START_REF] Lu | Cognitive Twins for Supporting Decision-Makings of Internet of Things Systems[END_REF]. In systems engineering aspects, an international standard ISO/IEC/IEEE 42010 -Systems and software engineeringarchitecture descriptionis officially recommended for describing the system architectures as a reference practice [START_REF] Capilla | 10 years of software architecture knowledge management: Practice and future[END_REF]. As R. Capilla et al., [START_REF] Kavakli | WiP: An architecture for disruption management in smart manufacturing[END_REF] explained, the ISO 42010 has provided meta-models for describing systems and software architectures. The specification concluded that most of the key concepts and meta-models in different architectural knowledge management (AKM) tools are consistent. E. Kavakli et al., [START_REF] Obergfell | Viewpoint-Based Methodology for Adaption of Automotive E/E-Architectures[END_REF] use the proposed architecture model to produce specifications for a smart system for disruption management. They proposed informational, physical and logical viewpoints to frame the stakeholders' concerns. P. Obergfell et al., [START_REF] Terzakis | EARS : The Easy Approach to Requirements Syntax[END_REF] used the reference architecture description to specify functional capabilities of modern automobiles from various aspects including services, software, electronics and electrics. They have applied their so-called Electric/Electronic-architecture (E/E-architecture) description method for identifying the Adaptive Cruise Control (ACC) features.

From the literature review, we found DT has been widely proposed by different domains with specific definitions and concepts [START_REF] Lu | Cognitive Twins for Supporting Decision-Makings of Internet of Things Systems[END_REF][START_REF] Tao | Digital twin driven smart manufacturing[END_REF]. A general architecture concept for DT is needed to identify domain-specific requirements for DT development. We found ISO 42010 has been widely used to formalize the architectures of complex systems and can potentially support DT architecture descriptions from different perspectives.

3

Systems engineering approach to identify the requirements of a digital twin

In this paper, a systems engineering approach is proposed to formalize the requirements used for making decisions on DT development. DT developers make use of ISO 42010 to identify the architecture of DT and propose questions to represent views of DT. Then based on an Easy Approach to Requirements Syntax (EARS) [START_REF]INTERNATIONAL STANDARD ISO / IEC / IEEE Systems and software engineering -agile environment[END_REF], requirements are formalized referring to answers to the proposed questions. Fig. 1 shows how the requirements are captured in order to make DT development decisions.

DT developers

ISO 42010

Questions

EARS approach

Requirements

Formalize

Answered by Support Decision-makings

Design questions

Fig. 1. Workflow of the proposed systems engineering approach

Identify questions using ISO 42010

From literature reviews, we used the international standard ISO/IEC/IEEE 42010 as the reference model, aiming at defining the key architectural concepts and system boundaries for DT from domain-specific perspectives, particularly for the Swiss Innovation Project IMPULSE.

Fig. 2. Reference Architecture in ISO 42010 [11]

To focus on the DT requirements, we simplified the model to investigate the core conceptual elements of the DT architecture; System-of-interest, Stakeholder, Concern, Architecture Description, Architecture Viewpoint, and Viewas shown in Fig. 2.

The System-of-interest refers to the collection of physical and virtual entities in a DT. Stakeholders interested in the DT (System-of-interest) each have their concerns, for example, DT system developers want to obtain the structure of the physical entities. The architecture description identifies the system-of-interest, the stakeholders and their concerns. It is comprised of more than one architecture view addressing a set of stakeholders' concerns and more than one architecture viewpoint. An architecture viewpoint is a work product that provides a framework for a set of concerns by presenting conventions for constructing, interpreting and using architecture views. An architecture view is a product addressing a (set of) concern(s) raised by the identified stakeholders.

In this paper, the system-of-interest is defined as the collection of physical and virtual entities of the DT which is being developed. The boundary is identified by considering the main stages of the DT system's lifecycle: concept, development, implementation, utilization, support, and retirement [START_REF] David D | For INCOSE member[END_REF]. Stakeholders are identified within that boundary while envisioning the phases of the DT's lifecycle. The term 'actor' (with defined roles) is used within Service Dominant logic [START_REF] Schmitt | First-Order Logic[END_REF]) and 'beneficiary' identifies where value accrues; these terms are complementary to the Systems Engineering term of stakeholder: stakeholders are actors directly involved with, or one-step-removed from the focus. Stakeholders are identified by the classification of different actors (roles). They provide concerns in order to identify the viewpoints and views. The onion diagram of product stakeholders [START_REF] Alexander | A Taxonomy of Stakeholders[END_REF] clearly details the taxonomy of stakeholders and their relationships. The concerns of the Digital Twin's stakeholders can be categorized based on various viewpoints such as performance, asset safety, etc. These viewpoints and views construct an architecture description of DT. Finally, questions for DT development are followed by answers (given by the use case owner) in a semi-formal format and proposed as views to DT developers to identify requirements for DT development.

Define Requirements using an EARS approach

The EARS approach is proposed to formalize the requirement syntax using a semiformal approach. The requirement is defined as a statement as following:

1. What a system must do (Functional Requirements). 2. A known limitation or constraint on resources or design (non-Functional Req.).

How well the system must do what it does (non-Functional Requirements).

The functional requirement is defined as a general syntax for functional requirements:

ReqF={[Trigger], [Precondition], System, System behavior, [Object]} (1)
Where square brackets (e.g., []) refers to the elements which can be removed. Trigger refers to when a System or others implement actions. Precondition refers to the conditions when a System or others implement actions. System refers to the target system implementing some actions (System behavior) to Objects.

In the EARS approach, requirements are defined as:

1. Ubiquitous refers to the system behavior always occurring. 2. Event-driven refers to the requirements for certain system behaviors.

3. Unwanted behaviors refer to the system behaviors under unwanted conditions. 4. State-driven refers to the system behaviors while in its own states. 5. Optional features refer to the system behaviors under specific conditions. 6. Complex refer to requirements constructed by collections of the above.

Table 1. EARS approach for formalizing requirements

Requirement type Format rules Ubiquitous

The <system or component> shall <system behavior> ([Object]).

Event-driven WHEN <trigger> <optional precondition> the <system> shall < system behavior > ([Object]). Unwanted behaviors IF <unwanted condition or event>, THEN the < system or component > shall < system behavior> ([Object]). State-driven WHILE <system statement>, the < system or component > shall < system behavior> ([Object]). Optional features WHERE <feature is included>, the < system or component > shall < system behavior> ([Object]). Complex Combination of the above requirements using first order logic [START_REF] Lu | Cognitive Twins for Supporting Decision-Makings of Internet of Things Systems[END_REF].

Use case

In order to evaluate the proposed approach, an industrial use case is investigated. First, stakeholders across the lifecycle of Digital Twin (from Developer, Implementer, User, and Maintainer/Supporter) are identified. By interviewing them, their concerns are collected. Then, four main architecture viewpoints are proposed to frame those concerns.

Use Case Overview

Company A seeks to add value to its business by offering new asset condition monitoring with control capabilities to its customer (Company C). Company C owns critical rooms and assets including server equipment where their temperature has to be monitored and controlled with special care. Company A has two partner companies: Company B and Company D; the former supports Company A in developing, implementing, and maintaining the DT and the latter in the support phase of the DT lifecycle. The DT is designed for constant monitoring of temperature profiles in parts of the room as well as the status of specific artifacts such as servers, door/window (being open/closed), HVAC systems, etc. The DT will also be coupled with simulation capabilities to run what-if scenarios and offer potential solutions including control command suggestions to secure proper functioning, and optimal post-failure reaction processes.

Systems Engineering Analysis

Using the systems engineering approach, we interviewed the stakeholders related to the use case. Fig. 3 illustrates the dependencies from stakeholders (blocks in blue) to viewpoints (blocks in green). Blocks in yellow represent categories of stakeholders, and the term 'stakeholder' refers to all the main people/teams involved across the DT lifecycle.

Each stakeholder has their own concern(s). The developed viewpoints frame multiple concerns which are raised by one or more stakeholders. By considering all stages of the Digital Twin from concept to retirement, main stakeholders in the use case are identified, followed by the various concerns they haveas shown in Fig. 3.

Fig. 3. Dependencies between actors, stakeholders, concerns and viewpoints

Based on the concerns in each viewpoint, questions are proposed to identify views, then the answers are formalized using the ERAS approach. Proposed examples of questions and answers are shown in Table 2. They are used to capture the requirements of the DT development in the use case.

Limitations

In the use case, only one service scenario for one customer (Company C) is explored. The stakeholders are identified from actors related to the DT. More stakeholders can be defined in order to capture more complete requirements. However, based on the scope of the IMPULSE project, several key stakeholders were selected to evaluate the approach given in this paper. The whole analysis process demonstrates the systems engineering analysis for the DT required by the use case. More detailed requirements will be analyzed in the future. This paper is limited to the requirements identifications as one of the earliest efforts prior to initiating the DT development phase. Nevertheless, based on the output of this paper, the work is continued further on to identify all the DT's entities in each use case, classify those entities in relation with each other using ontology languages and finally propose a reference architecture for DTs.

Table 2. Questions used for formalizing views

Viewpoints Examples of questions for representing views Business decision 1. Would the DT raise customer satisfaction? WHEN <the DT is operational> the <DT> shall < improve system reliability through failure detection and improving reactions> so that < operations of company C can carry out their core businesses to a high degree of satisfaction>.

Would the DT help Company A reach new customers?

WHEN <DT solution service is offered by the owner> the <DT> shall <provide further benefits to a previously unidentified group of customers, in a way that they are willing to benefit from Company A in exchange>. Organizational 1. How can twin project development and management lead to the execution of a successful DT solution? When <service concept consultants and project managers> guide <the project work, to focus on obtaining the highest value from their activities> the DT solution <shall meet and fulfil the needs of all actors in the ecosystem so that they can execute their own business goals successfully>. 2. In case of a failure and detection by the DT, how should responsibilities be distributed among various actors? When <the DT is operational> various failure alerts shall guide <facility managers through the reaction process> so that <they can deliver their service level agreement to the pipeline operators>. Performance & functionality 1. Would the DT be able to meet the predefined specifications? The <sensors> shall <remain continuously operational and functional>. The <DT> shall <produce automatic periodic reports>. The <DT results> shall <continuously be displaying monitoring data>. The <DT> shall <alert when data exceeds boundaries and assist with that specific reaction process>. 2. How can we be sure the critical assets work continuously and reliably? The <Digital Twin> shall <constantly provide asset operational data to Company A, Company C and facility managers; additionally, routine physical inspections are carried out.> Safety 1. How can this DT system improve asset safety? WHEN <the DT is operational> it shall <improve multiple process of MEBAG, various departments of Company C and Company D> so that <all equipment operates as should that supports the other critical reliant equipment in this system to improve overall asset safety>.

Conclusion

In this paper, we proposed a Systems Engineering approach to identify requirements, in order to support decision-makings of DT development. The systems engineering approach uses ISO 42010 to identify the architectures of DT and provide questions for capturing the requirements. Based on such questions, requirements are formalized using an EARS approach. Finally, a use case from the IMPULSE project is used to evaluate the approach. From the results, we find the requirements are identified to support decision-making for developing the DT with features to monitor and control the temperature in critical areas.

Acknowledgement

The work presented in this paper is supported by the EU H2020 project (869951) FACTLOG-Energy-aware Factory Analytics for Process Industries and EU H2020 project (825030) QU4LITY Digital Reality in Zero Defect Manufacturing and the Innosuisse (Project 35258.1 IP-SBM) IMPULSE project on Digital Twins. The authors also would like to thank the Lucerne University of Applied Sciences and Arts and the Zurich University of Applied Sciences for supporting this work.


Charlotte Wadoux

Which Way to Go from Here? Conference Report on (Neo-)Victorian 'Orientations' in the Twenty-First Century

The sunny seaside city of Málaga, Spain, provided a welcoming atmosphere for the conference (Neo-)Victorian Orientations in the Twenty-First Century. The conference aimed to investigate the concept of orientation as a critical tool to analyse time, space and relations between bodies in (neo-)Victorian fiction and other media.

As the main conference organiser Rosario Arias (University of Málaga) reminded us in her official welcome address, the conference concerns echoed those of the 2007 conference that took place in Exeter, UK, on Neo-Victorianism: The Politics and Aesthetics of Appropriation, showing that the field of neo-Victorian Studies is still expanding and renewing itself. The Málaga conference, Arias emphasised, thus offered an opportunity to "pursue new lines of enquiry, looking back to the past, to appreciate what has been achieved and look to the future". The conference formed part of the 'Orientation: Towards a Dynamic Understanding of Contemporary Fiction and Culture' project funded by the Spanish Ministry of Economy, Industry and Competitiveness (Ref. number FFI2017-86417-P), carried out by Arias and a core and an associate team. 1 As the round-table devoted to the presentation of the project showed, 'Orientation' may be understood in various ways. First of all, it reminds us of Sarah Ahmed's phenomenological study of the concept, to which many contributors referred. For Arias, orientation brings together temporality and space and

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Neo-Victorian Studies 12:1 (2019) DOI: https://doi.org/10.5281/zenodo.3471466

CC BY-NC-ND thus enables her to further her ongoing research on the trace. But Orientation can also be interpreted in relation to retrospection, as Carmen Lara Rallo (University of Málaga) pointed out. The polytemporality of the trace and its application to the study of space allows for a renegotiation of the perception of time both as dynamic and as palimpsestuous. Martyna Bryla (University of Málaga) offered to look at Orientation and Orientalism, putting Edward Said in dialogue with Ahmed. In particular, Bryla drew attention to Said's theories on discourse and dominance, to the way in which the Orient is composed of layers of mental maps and of stereotypes. In terms of Orientation, the focus therefore is on the relation with the 'Other', offering a possible renegotiation of the dichotomy 'Us/Them', which also relies on affect, resulting in emotional cartography. Similarly, Laura Monròs Gaspar (University of Valéncia) considered Orientation in the context of mapping the active role of women in theatrical productions of classics in the nineteenth century. These various contributions shared the underlying concepts of the trace, polytemporality, relationships, connections and intertextuality.

The Keynote Lectures

The first keynote lecture by Susana Onega (University of Zaragoza) offered a new perspective on a staple of intertextuality by renegotiating the concept of the palimpsest. As Onega argued, the palimpsest is not merely a metaphor for intertextuality, but may be used as a way to understand the multiple layers of history. Drawing upon Jacques Derrida's work on the one hand, and Nicolas Abraham and Maria Torok's on the other, Onega suggested that the palimpsest entails a form of spectrality. She brought to the fore the necessary active participation of readers when confronted with intertextuality, identifying "a palimpsestuous relation to the text, a risky relation". Onega offered a queer reading of John Fowles's The French Lieutenant's Woman (1969), showing that access to the past is obtained through the palimpsest, the spectralisation of reality, and the fantasy of the living dead. For her, the encounter between the protagonists Charles and Sarah is marked by "surprisingness" and disorientation, as Charles is not prepared for this queer moment marked by apocalyptic terms. Onega suggests that the novel sheds light on our own post-situatedness, so that our way of engaging with the Victorians parallels our mentality. Therefore, the palimpsest might offer a move away from 'writing back' towards a more transnational view with multiple centres. As Onega claimed, the more critical and peripheral readings we do, the better to bring forth new perspectives. This resonates with a recent effort in Neo-Victorian Studies and elsewhere to look at forms of neo-Victorian fiction/media emerging from other areas than the Anglophone world.

The next keynote lecture was presented by Marie-Luise Kohlke (Swansea University), who looked at neo-Victorian biofictions from the 'periphery', namely Richard Flanagan's novel Wanting (2008) and the mock memoir The Secret Life of Queen Victoria: Her Majesty's Missing Diaries (1979) written and illustrated by Jonathan Routh. Kohlke raised the question of ethics, especially when considering the biographical choices made by the authors. She argued that to some extent biofiction writers can be described as "stealers of souls, making the dead dance anew". For her, the omissions, choices, and supplementations in the re-presentation of the Victorians manipulate readers' feelings and cognitive endorsement, thereby orienting the way they read and interpret the past. In the end, Kohlke argued, neo-Victorian biofictions are haunted by authorial choices made and not made. Kohlke's talk thus calls for further attention to reception as well as production contexts of neo-Victorian fiction, and especially biofiction, as well as to the way such fictions shape our understanding of the global nineteenth century and its inhabitants. She ended her talk with the poem 'Wanting' by Niall Casson (see Still She Dances in this issue), a direct response to Flanagan's novel that refuses the traditional take on Mathinna's story by not reinscribing her as dispossessed.

The third keynote by Patricia Pulham (University of Surrey) also tapped into the way in which the Victorian past is constructed and conveyed to us, opening with an extract of Jacob Rees-Mogg's much criticised new book, The Victorians (2019). Mogg's book makes Pulham following remark even more pressing: "it is time for neo-Victorianism to re-orient its relation with the Victorians and ask 'where do we go from here?'" Pulham stressed the uneasy position of neo-Victorian Studies within the academy, highlighting a tension between literary theory, creative writing, nineteenth-century and contemporary literature studies. Pulham's talk uncovered the various problems that increase this tension: the problem of value and 'authenticity', periodisation, and the prestige of disciplines long associated with difference and separation rather than continuity. Drawing on Pierre Bordieu's work, Pulham pointed out that nineteenth-century "cultural capital" problematically eclipses that of twentiethand twenty-first century writers. Pulham called for a need to think of neo-Victorian Studies as transcritical, thereby emphasising fluidity and continuity in a post-postmodern world rather than fragmentation and separation. This talk clearly contributed to the debate over our role as literary scholars and the way literary teaching and theory shape literature and certain monopolies.

The final keynote lecture was delivered by Ann Heilmann (Cardiff University), who focused on a Pre-Raphaelite icon, Elizabeth Siddal, whose death marked the beginning of her resurrection and rebirth in art and painting, starting with Gabriel Dante Rossetti's Beata Beatrix (1870), described by Heilmann as a "moment frozen in time". Looking at later biofictional neo-Victorian works, Heilmann wondered to what extent contemporary texts can re-orient Siddal with reference to her own work as an artist rather than just as a model to the Pre-Raphaelites. Heilmann articulated the paradox in our relation to Siddal, which stems from the voyeuristic gaze of the Victorians onto her body that finds a reflection in our own gaze, even as we try to recover her as an individual, away from her former objectifications. Siddal has now gained the status of mythical supermodel, and Heilmann looked at the way she is reinvented in neo-Pre-Raphaelitism, whether she is given a voice of her own (or not), and whether she is re-objectified in the process. Heilmann's various case studies problematised the mediation of history, pointing out the importance of the medium used for re-orientation; hence her choice to focus on a wide range of sources such as novels, poetry and TV series. For Heilmann, resistance to the tale of the supermodel can only be achieved through resistance to the commodifying male gaze.

The four keynote lectures raised issues that were complemented by the varied and plentiful talks from international contributors. The following is a non-exhaustive summary of the main topics discussed during the symposium.

2.

Looking at Various Media: Opening New Directions Heilmann's lecture was supplemented by a talk on the series Desperate Romantics (2009) by José María Mesa Villar (Catholic University of Murcia) who discussed the filmmakers' biographical choices in the context of the revival of the Rossetti and Siddal myth. The dialogue between the novel and visual media, such as the photograph, came to the fore in a paper on Helen Humphrey's Afterimage (1992) by Charlotte Boyce (University of Portsmouth). Other, less studied media were also covered. Sarah E. Beyvers (University of Passau) investigated videogames and the new forms of engagement with the Victorian this immersive medium provides its audience with. Charlotte Wadoux (University of Kent / Université Sorbonne Nouvelle Paris 3) explored a French graphic gamebook rewriting Sherlock Holmes, Sherlock Holmes: La BD dont vous êtes le héros (2013), in which readers are themselves turned into a kind of detective. Anna Gutowksa (Linnaeus University) analysed the TV series Penny Dreadful (2014-2016) as a transfictional object, which offers new modes of thinking about intertextuality and our relation to the palimpsest. Jessica Cox (Brunel University London) considered popular fiction by Victoria Holt to demonstrate continuities that blur the still debated boundary between 'Victorian' and 'neo-Victorian', daringly suggesting that "there are no neo-Victorian texts, only neo-Victorian readers".

3.

Re-Orienting Our Relation to the Past A great number of presented papers revolved around historiography, focusing especially on the representation of the Other and on postcolonial neo-Victorian fictions. Both Jaine Chemmachery (Université Paris-Dauphine -PSL) and Susanne Gruss (Friedrich-Alexander-University Erlangen-Nürnberg) showed the ethical problems raised by the turn to 'Victorian subalterns' by looking respectively at Barbara Chase-Riboud's Hottentot Venus (2003) and at biofictions revolving around the figure of the Ethiopian Prince Alemayehu. For Gruss, the problem arises from the fact that 'Victorian' is too often used as a shorthand for 'Empire', but also because writers 'sex up' the Victorian as exotic queer Other. Eulalia Piñero Gil (Autonomous University of Madrid) also looked at Saartje or Sarah Baartman's afterlives and the way in which she functions as a form of revenant that infiltrates our present to tell the stories of marginalised women. As was suggested in the discussions, the numerous appropriations that are being published (be they ethical or not) beg the question of the extent of their capacity to activate a necessary haunting as part of our engagement with the past. Such reflections once again highlighted the problematics of biofiction tackled in Kohlke's lecture.

Papers also engaged with the revision of key historical narratives and events such as the search for the North Pole. In her paper on Richard Flanagan's Wanting, Maria Jesus Cabarcos (University of A. Coruña) drew connections between considerations on the Orientalised Other and North Pole expedition narratives. Cabarcos argued that Flanagan's take on British colonialism is ambiguous, partly re-inscribing the colonial ideologies it supposedly sets out to criticise. In contrast, Ingibjorg Austsdottir (University of Iceland) demonstrated the possibility to truly write back by focusing on popular fiction revisiting Scottish explorations and the narrative of women waiting for the return of their menfolk from expeditions. Austsdottir showed how historical and neo-Victorian novels today constitute platforms for challenging dominant cultural narratives, thereby pointing out how history is always already fictional. Petr Chalupski (Charles University) looked at the way in which novels on Artic exploration, particularly Ian McGuire's The North Water (2016), discuss ethical questions of good and evil by entering a dialogue with Joseph Conrad's Heart of Darkness (1902).

4.

Orientation and Female Voices Numerous papers were devoted to the representation of women in neo-Victorian fiction. Ana Chapman (University of Málaga) and Leopoldina Pedro Mustieles (University of València) both investigated the trope of voice in, respectively, Michel Faber's The Crimson Petal and the White (2002) and Penny Dreadful. While Chapman used Jacques Derrida's concept of hospitality to analyse the immersion process at play in Faber's novel, which articulates the voiceless of the nineteenth century, Mustieles focused on the limitations of the liberation plot in Penny Dreadful. Ashleigh Taylor Sullivan (Swansea University) gave a paper on the haunting persistence of the Victorian Gothic by looking at the impact of Jane Eyre (1847) on Daphne du Maurier's Rebecca (1938) and Sarah Waters's The Little Stranger (2009), showing how the domestication of the Gothic in the Victorian era is incorporated into the neo-Victorian project, in which women and houses are always haunted by preceding women. Sarah Waters's novels provided the focal point for multiple papers during this symposium, with presenters approaching her work in a wide range of ways. Elsa Adán Hernández (University of Zaragoza) focused on Tipping the Velvet (1998) and the way in which the Victorian past is used as a tool to bring marginalised women to the foreground, looking especially at performativity and the process of queering in the novel. Akira Suwa (Cardiff University) discussed Park Chan-wook's The Handmaiden (2016), a Korean film adaptation of Fingersmith (2002), demonstrating the way in which new possibilities for neo-Victorianism open up in a global context, especially through representations of heterotopia and the double colonisation critiqued in the movie. Olga Dzhumaylo (Southern Federal University) also talked about Fingersmith and its intertextual dialogue with Dickens's Oliver Twist (1839), arguing that Waters makes something new out of Dickens by bringing a sensory, immersive experience of being a woman in the nineteenth century to the reading process. Finally, Laura Dominguez Morante (independent scholar) considered Fingersmith's use of pornography in terms of Maud's self-construction, which is achieved through a process of annihilation and (re-)creation, thus epitomising the rewriting of the past as a liberating narrative.

5.

City and Detection Last but not least, the theme of the city in conflation with that of detection was very much present during the conference. Eliana Ionoaia (University of Bucharest) focused on two neo-Dickensian American novels, Dan Simmons's Drood (2009) and Matthew Pearl's The Last Dickens (2009), both engaging with Dickens's unfinished last novel, The Mystery of Edwin Drood (1870) to represent London as a hellish city and Dickens as a ruthless self-made man. Kym Brindle (Edge Hill University) also looked at novels involving enigmas as she focused on contemporary crime fiction offering a pastiche of Golden Age detective fiction. While approaching neo-Victorian fiction from this angle may seem surprising, Brindle argued that such pastiches highlight key tropes such as class division, gender oppression and, above all, sensation. These pastiches unashamedly relish violence, causing Brindle to wonder whether neo-Victorianism contributes to our society's desensitisation to violence.

Violence, of course, is a key trope appearing in numerous neo-Victorian crime TV shows today, especially in reimaginings of Jack the Ripper's killing spree. Elisavet Ioannidou (Aristotle University of Thessaloniki) looked at the city and the metaphors of the maze and the labyrinth to discuss neo-Victorian relations with the past. She focused especially on the series Ripper Street (2012Street ( -2016) ) and its labyrinthine way of engaging with the Ripper murders, which again provides a hellish vision of the city. Ioannidou sees a progressive shift in the series from a unicursal labyrinth to a multicursal maze, which tropes intertextuality. The paper by Barbara Braid (University of Szczecin) also tackled urban palimpsests in her investigation of Alan Moore's From Hell (1989) and of the TV series Whitechapel (2009)(2010)(2011)(2012)(2013). Looking at the influence of dark tourism on these fictions, Braid demonstrated the way that Whitechapel is construed as a lingering wound in the body of London. Her paper tackled the problematic trauma and loss that lie at the centre of Ripper literature, thus questioning the possibility for neo-Victorian fiction to heal past wounds.

6.

Future Directions The symposium gathered researchers from all over the world and at various stages in their careers in Málaga's dazzling May sunshine. An afternoon reception in the university's beautiful botanic gardens added to the atmosphere, while regional wine and tapas aroused culinary curiosity and appreciation. A real sense of 'neo-Victorian community' emerged from these intense three days. The conference was the occasion of a collaboration between researchers at various stages: a large number of PhD students were present, from Spain and elsewhere. The conference highlighted the multi-facetted nature of the neo-Victorian project and the field of neo-Victorian Studies, providing us with new ways of considering what may be called the emergent 'neo-Victorian canon' while offering new areas and tools for future reflection.

Indeed, the conference contributed to further map neo-Victorian studies, underlining landmarks in the field such as the importance of the representation of the city, the articulation between postcolonial and neo-Victorian theory, the multiple uses of the concept of palimpsest and of the genre of biofiction. The association between sexual orientation, queer theory and neo-Victorian fiction has tended to focus on Sarah Watersthough other readings of the latter's works were offered too as we have seen.

Nevertheless, the conference also mapped new directions for neo-Victorian studies. Sarah Ahmed's concept of orientation certainly proved to be a useful conceptual framework for new directions and perspectives on our engagement with neo-Victorian fiction and other media. Also, if a lot has been written on Darwin's explorations and responses to Darwinian discourse in neo-Victorian literature, there is much less criticism of narratives focusing on Arctic explorations -other than Franklin's, which (1946), thereby calling for an opening up of our so-called neo-Victorian canon.

Notes

1. For more detail on this project see: https://orionfiction.org.

  is often discussed in relation to Wanting or Dan Simmons's The Terror Conference Report on (Neo-)Victorian 'Orientations' _____________________________________________________________ Neo-Victorian Studies 12:1 (2019) DOI: https://doi.org/10.5281/zenodo.3471466 CC BY-NC-ND 221 (2007). The conference also reinforced the growing interest in popular fiction and media, looking at new materials, from Golden Age detective fiction to historical novels set in the 1920s and the movie It's a Wonderful Life

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Neo-Victorian Studies