Functionality and Aesthetics of Furniture-Numerical Expression of Subjective Value

In the recent years the habits of buying furniture have changed. The fabrication of individual pieces of furniture is increasingly coming to the forefront. A personal contact is being established between the customer and the furniture, which is a relationship of one (product) to one (customer). In order to satisfy the individual demands, higher quality as well as higher prices appeared as a necessity. The competition is beginning on the market, where emotion becomes a signifi cant factor in decision-making process. Therefore, functionality and aesthetic functions, determinative forms and fashionable style play a very important role in furniture design and production. The objective of the paper is to report research results on how functionality and aesthetics of different styles of furniture could be determinated, measured and how they infl uence customer requirements and demands. To establish the proportion of functionality and aesthetic features, a numerical expression of the functions was defi ned by using various designers’ methods such as Ranking Method Quality Development (RMQD) and Failure Mode and Effects Analysis (FMEA). It is shown that both methods could be used very effectively for designed and marketing oriented furniture, for modelling customer satisfaction as well as in connection with aesthetic functions, assuring the quality of the product in the planning stage.


INTRODUCTION UVOD
The world of furniture market is getting more complex than it was before.In order to measure consumers needs, preferences and habits, it is important to improve contemporary values of furniture.In recent years, it is evident that the habits of bying and using furniture have been changed (Domljan et al., 2006;Horvat et al., 2008).The fabrication of individual pieces of furniture is increasingly coming to the forefront.A personal contact is being established between the customer and the furniture, which is a relationship of one (product) to one (customer).In order to satisfy the individual demands, higher quality as well as higher prices appeared as a necessity.In the competition that occurs on the market, when choosing furniture, preference is given to individuality and emotions (Domljan and Grbac, 2014).Of course, there are various factors that also infl uence customer decisions when buying furniture: price, quality, reliability, etc. (Raport DTI, 2005).Therefore, functionality and aesthetic functions, determinative forms and fashionable style play a very important role in furniture design and production.Those parameters, usually connected with visual parameters of the design, are measureable, as well as other designers parameters appearing in the product, by using special designers methods such as Function analysis, Questionnaire research, Ranking Method Quality Development (RMQD) and Failure Mode and Effects Analysis (FMEA) (Antal, 2007;Laurel, 2003).
The objective of this paper is to report research results on how function and aesthetics of different styles of furniture could be determinated, measured and how could they infl uence the customer requirements and demands by using RMQD and FMEA methods.

Defi nition of functionality and aesthetic functions Defi nicija funkcionalnosti i estetskih funkcija
Function can be expressed as the properties related to the use of a product.These properties include the relation between a product and a consumer (Antal, 2007).
On the basis of purchasing motivation, the system of functions can be divided into: -functionality (e.g.utility and practical function) and -aesthetic functions (e.g.visual sensation, emotions).
Aesthetic value is considered to be the effect (or style) of objects as to what degree they can teach us to perceive or understand the appeal of beauty (Eco, 2004).Nevertheless a designed object, such as a piece of furniture, can be evaluated regarding whether beauty is involved in it, or not.
Aesthetic value means the complexity of the properties of objects, devices or equipment, which provide appeal, pleasure and good experience when it comes to sensation, action or indirectly, to the general human state of health related to a given object (Antal, 2007).
In industrial design, objects are created with the intention to satisfy not only aesthetic criteria but also criteria of utility and practical function (Papanek, 2005).These features are inseparable.In the products such as furniture they can only appear jointly."Being useful also means being beautiful.(...) There is no separate usefulness and beauty, but what is useful is considered beautiful as well" (Lissák, 1997).There has to be a suitable combination of usefulness and beauty.In contemporary world, people generally buy furniture in order to use it as well as to take pleasure in it.It is essential, however, to determine the proportion of functionality and aesthetic functions in case of furniture?This proportion has to be determined to satisfy consumer demands.To establish this proportion, both functionality and aesthetic functions have to be measured.It is important to notice that there is still no exact method that could determine precisely the proportion of these functions.A number of experiments have been carried out, but the exact defi nition of aesthetic functions has been based on modelling consumers' value judgements (Antal, 2007).The quality of two similar products can be measured on the level of function satisfaction.The satisfaction measure determines which product is better, more beautiful and more attractive (Lissák, 1997).
Optimal aesthetic quality of a product depends on the proportion of A/B, represented in the section a-a.This proportion is to be designed according to customer demand, i.e. in an optimal way. Figure 1 presents the essence of the success of a product.This idea is being emphasised, regarding all a-a: position of furniture on the scale A/B: proportion of functionality and aesthetic value If value concerns to the whole product, all functions of the product have to be taken into consideration.If it affected only one or two functions or group of functions, F and CF would have to be determined according to the examined functions.A product consists of subsets of functionality and aesthetic functions, which mostly means the aesthetic quality of the product.The proportion of functionality and aesthetic functions is optimal if it meets the demands of consumers (Antal, 2007).
According to Hegedűs (1994), aesthetic functions are analysed separately from functionality.Both functionality and aesthetic functions have their own values.
As an example, if functionality of a product is taken as: and the aesthetic functions of a product are: E 1 , E 2 ,…E j ...E m ; it follows that: h i is the value of H i ; and e j is the value of E j If these functions are linked to the product, which is supposed to satisfy the customers' needs, it can be expressed as follows: Using these values, the proportion of functionality and aesthetic functions can be expressed by the formula: (1) As an example, Table 1 shows the selected functions of a product that could be observed and analysed.
Using the formula (1) and data presented in Table 1, it can be written as follow: (2) The optimization means a constriction within an interval on the basis of a criterion.With numerous sampling, a/b rates can be defi ned and evaluated, as well as the customer satisfaction (rate of satisfaction).The probability value of weighted rate shows the optimum scale (proportion).The type and specifi cs of distribution can be determined and by means of the bottom and upper limits of confi dence intervals of e.g.95 % (Figure 2).
For example, if the value is: -2σ<a/b<+2σ, it can be declared that a) furniture is aesthetically acceptable or b) furniture is exclusive.
Aesthetic numbers for the practical expression of the relation can be suggested and the applicability of the theoretical relation for furniture can be reviewed.

Designers' methods applied to measure
requirements and optimal proportion of the product 1.3.Dizajnerske metode primjenjive za mjerenje zahtjeva i optimalan omjer proizvoda Customers needs are the fi rst step in defi ning a number of requirements of the product.It means that it is necessary to establish designers' factors such as functionality, aesthetics, ergonomy, economy, technology and many others for the development of a product (Domljan et al., 2006).Identifying customer needs means creating a high-quality information channel from the customers to the product developers.It will ensure that those who directly control the details of the product, including product designers, understand the needs of a customer.These needs have to be organised into a hierarchical list in order to be more understandable.The methods (for example designer's or manager's methods) that can be used for identifying customer needs are interviews, focus groups, observing the product in use or simmilar.
The customer needs are helpful to defi ne the functions of a product.To achieve it, the needs have to be transformed into functions.Functions are abstractions of what a product should "do".A limited number of elementary or general functions on a high level of abstraction create a function structure.The functions are organised into a hierarchical order, in a so called "tree structure" (Antal, 2007).
From designers' point of view, it is very important to know what kind of methods are used to determine an optimal proportion of the product requirements and for what purposes the proportion could be used.Some of designers' methods are presented below.

Function Analysis 1.3.1. Analiza funkcija
Function analysis is a method for analysing and developing a function structure.A function structure is an abstract model of the new product, without material features such as shape, dimensions and materials used.It describes the functions of the product and its parts and indicates the mutual relations.In function analysis, the product is considered as a technical-physical system.The product functions consist of a number of parts and components, which fulfi l sub-functions and the overall function.By choosing the appropriate form and materials, a designer can infl uence the sub-functions and the overall function.The principle of function analysis is to specify what the product should do and then to infer what the parts -which are yet to be developed -should do as well (Boeijen et al., 2013).
By selecting aesthetic functions from the tree structure and by using them in Failure Mode and Effects Analysis (FMEA), the aesthetic quality of the product in the planning stage can be assured.The measure of the aesthetic functions has become possible by functions value and the weight numbers of determinative style.Failure Mode and Effects Analysis (FMEA) is a model used to take priority potential defects based on their severity, expected frequency, and likelihood of detection.The FMEA can be integrated into product development or product manufacturing process and used to improve the design or process robustness.The FMEA highlights weaknesses in the current design or process in terms of the customer needs and is an excellent tool to take priority and organise continuous improvement efforts in areas that offer the greatest return.The process is very straightforward and begins by identifying all of the probable failure modes.The analysis is based on experience, review and brainstorming and should use actual data, if possible (MoreSteam, 2014).
The Failure Mode and Effects Analysis model can help teams decrease project scope and complexity by focusing on the primary failure modes of a process.The FMEA can be best created by coordinating a crossfunctional team and using objective and subjective knowledge to identify accurate properties about the identifi ed failure modes.
This method can be used by taking into consideration only aesthetic functions combined with function analysis.It means that both the aesthetic functions of furniture could be determined and the aesthetic characteristics and forms of furniture could be analysed.A The Ranking Method Quality Development (RMQD) is a method used for matching and comparison of furniture and concurrency analysis.The realisation of the functions of the determinative forms is defi ned by this method and ranked by the correspondence percent.
A threshold value can be defi ned as: -The pieces of furniture that are situated above this threshold value meet the requirements (e.g. they are exclusive).-The pieces of furniture that are situated below this threshold value do not meet the requirements (e.g. they are not exclusive).
Through the determining forms, the aim is to detect the proportion of aesthetic and functional properties by certain properties.The assessment factors can be measured by using some properties which are not of equal weight, but are ranked by the RMQD.This can help to create a basis for comparison, based on which it can be established whether these properties are inclu ded in the furniture and to what degree they are present.
An assessment method based on the overall emotions can be created.The method is aimed at determining the range of style properties for a given furniture collection.The algorithm presented below is suitable for applying this assessment method (Figure 3).The answer to the question: "What kind of furniture properties allow determining the style of a group of furniture" could be obtained with a questionnaire.On the basis of the answers, an order of rank may be formed and function structure of the furniture can be created in the FMEA process in order to select the aesthetic functions and to locate the critical characteristics.The functions with failed result are assigned by the elements of the furniture.For these functions the potential failures are identifi ed as well as the effects and reasons of failures.The control is established for preventing all potential failures.The effect and the level of satisfaction of the customer is analysed by the experts team if one of the aesthetic function is not satisfi ed.In this occasion, the disappointment of the customer is measured.For the aesthetic functions, the measurer relevance numbers are determined.The severity of the failure with these numbers is preferred.Example: if an aesthetic function is not satisfi ed, this is marked as a failure.The importance of the failure's effect (severity) can be expressed by a weight number.Scoring is made from the customer's perspective, on a scale from 1 to 10 (10 if the customer perceives the aesthetic value 100 %, 1 if the customer hardly perceives the value) (Table 2).
The next step is to assign a value on a 1-10 scale for the probability of occurrence, as well as for the probability of detection for each of the potential failure modes.After assigning a value, the three numbers for each failure mode are multiplied together to yield a Risk Priority Number (RPN).The RPN becomes a priority value to rank the failure modes, with the highest number demanding the most urgent improvement activity.
During the analysis determining the aesthetic functions of furniture and taking into consideration their realization rate, possibility will open to measure aesthetic functions and to improve the aesthetic quality of the furniture.The quality is optimized by eliminating all possible failures, locating their impacts and reasons before getting to the customers.the fi rst ten properties could be considered.The answers should provide some information on the fact to what degree (what percentage) the given pieces of furniture meet the criteria of a given style and what kind of weighted order should be arranged.The RMQD surveying system is also suitable for this kind of complex measurement.

MATERIJALI I METODE
2.1 Samples and team members 2.1.Uzorci i članovi tima For this research, fi ve groups of furniture were selected as the samples from different points of view.(style, price, materials).The rank of selection was high quality furniture made from solid wood.Quality in this occasion means high aesthetic, construction, technology and economics level of requirements.Groups of furniture samples used for the RMQD analysis were ranked from A to E (Figure 4 -8).
During the research, a team of fi ve experts (two designers, one wood engineer, one ergonomists and one design manager) from Hungary and Croatia was established with members from 34 to 50 years old.

Research phase 2.2. Faza istraživanja
The fi rst phase (preparation phase) in the research was to organise a team and determine the parameters.
The agreement coeffi cient of the team was over 90 %.The distribution of the team members' evaluation was ± 10 %.
The process of the research was determined by the steps as follows: -determine the task, meeting of team members, -study the collected documentation of the selected furniture, -study and accept previous steps of research as input results; e.g. 7 items out of 10 style properties were considered as characteristic of the style, -classify and weigh -compare properties and requirements, -select, analyse and compose 5 groups of furniture and rank their value on a 5-1 scale (5 equals the assessment factor of the furniture that complies best with the requirements), -evaluate the assessment factors individually (each member of the team), by means of the/an assessment list (Table 4)

REZULTATI I DISKUSIJA
After analytical data processing, the research results appear as follows: The agreement coeffi cient is over the required 90 %.The team member whose assessment range was over the standard threshold value was excluded by the computer when arranging the results.The weighted order of the assessment factors are presented in Table 3 and Figure 9.
The list of one of the assessing team members is shown as an example in Table 4.
The comparison of alternatives (two groups of furniture) is presented in Figure 10 and 11, taking into consideration the assessment factors.The fi nal results of the survey are shown in Table 5.The fi ve groups of furniture are in compliance with the former established criteria and assesments (Table 4).
Based on the results, a threshold value, e.g.70 %, was determined.Over this value, the furniture may be considered as exclusive.

ZAKLJUČAK
The demands of costumers are maximally satisfi ed when the proportion of functionality and aesthetic functions converge to the expectations of customers.The numerical expression of the subjective value judgment by designing furniture can be used for concurrency analysis and for quality examinations.An evaluating algorithm can be developed by using the RMQD.This method can be used very effectively for designed and marketing oriented furniture as well as for modelling customer satisfaction.FMEA could also be used in connection with aesthetic functions, assuring the quality of the product in the planning stage.

Table 2
Severity (Importance of failure)

Table 5
Order of samples from the most exclusive to the least exclusive furniture according to results Tablica 5. Poredak uzoraka prema rezultatima (od najekskluzivnijih prema manje ekskluzivnima)