Adaptive user interfaces for on-line shopping

L. Ardissono and A. Goy and G. Petrone and M. SegnanDipartimento di Informatica, Universit~ di Torino

Corso Svizzera 185; 10149 Torino; Italy{liliana, goy, giovanna, marino}@di.unito.it

Abstract

With the increasing popularity of on-line shopping, thepersonalization of the front-end of Web stores has be-come a critical issue: these systems are accessed bycustomers with different backgrounds, expertise andpreferences; therefore, their usability can only be im-proved by tailoring their interfaces to the needs of eachspecific user. In this paper, we present the personal-ization features offered by SETA, a prototype toolkitfor the creation of adaptive Web stores, developed atthe CS Department of the University of Torino. TheWeb stores created using SETA suggest the items bestfitting the customers’ needs and adapt the layout andthe description of the store catalog to their preferencesand expertise.

IntroductionThe popularity of Web shopping is increasing and dif-ferent types of (home and business) customers purchasegoods by accessing Web catalogs without relying onintermediaries. Noticeably, this trend does not onlyconcern traditional domains like the market of moviesand music, but also other newer domains, such as theelectric power trade (Ygge 1999). In all these cases,the user needs information about the alternative prod-ucts/services and their advantages and limitations, toidentify those satisfying her needs and constraints atbest. As discussed in (Benyon 1993), the users of soft-ware systems differ in their characteristics (e.g., status,expertise, preferences), which should be taken into ac-count to enhance the usability of such systems.

In several commercial tools for the creation of Webstores, like Microsoft Merchant, IBM’s Net Commerceand ATG’s Dynamo, the personalization of the interac-tion with the customer has been enhanced, in order toestablish a long-term relation with her (in contrast tothe typical one-shot interactions supported by the firstsystems). These tools tailor the suggestion of goods tothe user’s preferences (Resnick &5 Varian 1997). How-ever, they adopt quite simple (if any) techniques forpersonalizing the presentation of items.

Copyright (~) 1999, American Association for Artificial In-telligence (www.aaai.org). All rights reserved.

Although the suggestion of goods is a very impor-tant functionality, we believe that the interaction withthe user can be further improved by customizing thepresentation style, as well (Brusilovsky 1996): in fact,Web catalogs typically fail to provide the informationrelevant to the customer’s interests and, especially intechnical sales domains, they challenge the user withcomplex descriptions, understandable only by experts.

We have addressed the adaptivity issue in electroniccommerce, dealing with both the selection of itemssuited to the customer and the personalized presenta-tion of Web catalogs. In this paper, we describe thepersonalization features offered by SETA, a prototypetoolkit for the creation of adaptive Web stores devel-oped at the CS Department of the University of Torino.

Management of the user profiles

SETA exploits user models (Wahlster & Kobsa 1989;Chin 1993; McTear 1993) to customize the pages of theWeb store. Since the user of a Web store has to bemodeled both as the user of a Web system and as acustomer, the user models contain information describ-ing preferences towards the interaction style, as well asrequirements on product properties.

When a customer accesses a Web store created withSETA, her model is initialized either by retrieving herrecord from a users database, or by exploiting stereo-typical information about customers. In this way, a firstmodel can be quickly created for users visiting the storefor the first time. However, as stereotypical informationis not precise enough to characterize the individual cus-tomer, the system also exploits dynamic user modelingtechniques to update the user model in an unobtrusiveway, on the basis of her behavior.1

The user model is dynamically updated by monitor-ing the user during the interaction. We identified the

1When a new store is created, the store designer canchoose the user modeling techniques to be used: the storescan be configured to handle: a) a single, generic user model;b) individual, static user models instantiated by exploitingstereotypical information; c) individual, dynamic user mod-els, updated during the interaction with the user. Optionsb) and c) can be combined, as in our prototype Web store(Kass & Finin 1988).

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From: AAAI Technical Report SS-00-01. Compilation copyright © 2000, AAAI (www.aaai.org). All rights reserved.

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information about the user’s interests carried by eachtype of action she may perform (e.g., asking for techni-cal information about an item, adding an item to theshopping cart, etc.). During the navigation of the cat-alog, the system maintains in its working memory allthe relevant actions and periodically analyzes this eventhistory to revise the user model. The collected informa-tion is fed as evidence to a Bayesian Net that modelsthe dependencies among the user’s behavior and herinterests, domain expertise and features.

The pages of the Web store catalog

The goods are presented by means of two main types ofpage: the pages characterizing the product categoriesavailable in the store and those showing the items avail-able within each category. Figures 1 and 2 show twoexample pages produced by our main prototype, whichpresents products of the telecommunication domain.

The description of the product categories (e.g.,phones, answering machines, and the integrated prod-ucts) is aimed at providing the user with basic infor-mation about the offered functionalities. Instead, thedescription of the items (e.g., the phone models thatcan be purchased) is focused on the specific features of-fered by the items and on their properties. Both typesof information are important to the description of thecatalog: in fact, the characterization of a product cat-egory helps the user to identify the kind of productshe needs, while the description of the items enablesher to select the particular model suiting her needs atbest. Although the description of product categoriesmay seem trivial in simple domains, it is essential indomains where the user’s expertise may not supporther in the identification of her own needs.

Pages describing product categories

A page describing a product category provides the userwith information about the main functionalities of theitems belonging to the category itself. For instance,Figure 1 shows a page describing an integrated product:the "fax-phones with answering machine".

This type of page is organized in several areas, dis-playing the contextual information, the navigation andcontrol buttons and the description of the product cat-egory. More specifically:

¯ The topmost bar provides the links to the main prod-uct categories available in the store.

¯ In the leftmost portion of the page the system dis-plays the active interaction paths and enables theuser to switch among them. Each path representsa dialog context, that specifies:

- The target of the product: the user may considerproducts for home or business use (this informa-tion is displayed by means of an icon); moreover,she can look for a good addressed to herself, or tosomebody else. In this example, the user is look-ing for a product for her own office, and for anotherproduct, addressed to Mary, for home use.

- The initial selection: when entering the store, theuser is asked to select the main product categoriesshe is interested in. The system keeps track of thischoice by providing the label "Initial selection" anda link to the category itself. In our example, theuser initially selected the phones category.

-The last visited page (in each dialog context):while browsing the catalog, the user can move fromthe page showing the initial product category topages describing other products or showing the

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Figure 2: A page describing the "Scriba Compact 401" item.

available items. The system displays this informa-tion under the "Last visited" label. The currentcontext is highlighted and specifies the content ofthe page ("Now displayed" label). In the example,the user is looking at a page presenting the modelsof fax-phones with answering machine.

¯ The central area describes the functionalities offeredby the product category in the focus of attention andcontains the link which the user can follow if, on thebasis of the description, she decides to analyze therelated items ("models" link).This area also contains the link to view other productcategories. As described in (Ardissono et al. 1999b),the catalog is internally represented as a conceptualnetwork where product categories are related to oneanother on the basis of their functionalities. Thus,browsing the catalog has a direct correspondence tobrowsing the nodes of such network. In this exam-ple, the system is displaying the most specific prod-uct category which integrates the functionalities ofphones, faxes and answering machines; therefore, theuser is only allowed to move to simpler products, bymeans of the "BACK TO" link. When intermediateproducts are displayed, a second, "GO TO" link isshown, leading to more complex products.

¯ The bottom bar contains general control buttons,such as the one for inspecting the content of the shop-ping cart, or the "end of session" button.

The description of the offered functionalities is an effi-cient way to sketch the product categories, so that the

user can read a summary of the type of service offeredby the items belonging to the category. When a producthas to be presented, the system retrieves the linguisticdescription of each functionality offered by the productand composes such descriptions by means of a template,forming the complete natural language sentence whichis included in the central area of the page.

Pages describing items

The pages describing the items of a product categorydisplay specific information about the available models.See for instance Figure 2, which presents the "ScribaCompact 401" fax-phone with answering machine.

This type of page is organized in several areas, someof which are the same as those in the pages describingproducts; e.g., the top and bottom bars, and the left-most portion of the page. Moreover, the following areascontain differences:

¯ The central area describes the properties and featuresoffered by the displayed items. For each model, thearea devoted to its description contains:

- The name, a picture and the price of the item.- A button to add the item to the shopping cart, in

order to buy it later on.- A button to display the technical details.- The description of the properties and features of

the item. If the system shows only a subset of thefeatures, a link ("more information") is added see the whole list.

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¯ The lower area of the page, below the descriptionof the items, contains several buttons and links. Inparticular:

- The links for browsing the list of available models("previous items" and "next items"; only the sec-ond link is shown in the figure, which presents thefirst item of the list).

- A button to display the list of the models availablefor the current product category; the user can usethis list to request the description of a specific itemin a direct way, without browsing all the pages, viathe previous/next items links.

- A button to create a customized comparison ta-ble, by selecting the goods and the features to beexamined.

- The link for going back to the page describing theproduct category of the displayed item (in the fig-ure, fax-phones with answering machine).

Adaptivity issues

In the design of the structure of the catalog pages, wehave focused on two main issues: on one side, the visitorof a Web store needs to be guided by the system, thatshould present the information relevant to the identifi-cation of the goods satisfying her needs at best. On theother hand, the user must feel that the interaction is un-der her control. To comply with this requirement, thesystem produces catalog pages containing several but-tons that facilitate the execution of different actions.For example, the user is allowed to browse the catalogand to switch between different interaction contexts;she can analyze the items available for a product oneby one, ask for technical information about such items,create personalized comparison tables, view the list ofmodels available within a product and request the pre-sentation page for a specific item. However, in orderto guarantee the consistency of the interaction, the sys-tem constrains, at each step, the actions that the usermay perform, by enabling only those reasonable withinthe specific context. For instance, actions like addingsomething to the shopping cart, or asking for technicaldetails, are allowed only when the user is browsing theitems of a given product category and not when thecategory itself is described.

The system dynamically generates the pages of theWeb catalog, by exploiting personalization techniquesfor adapting them to the user. As far as the overallappearance of the pages is concerned, we have defineda small set of layout packages, mainly differing for theirbackground, font size and face, and other similar pa-rameters; the appropriate package is selected on thebasis of information such as the user’s age, her lifestyle, and other data characterizing her preferences to-ward the layout of the interface. Moreover, the systemadapts the amount of information displayed in the pagesof the catalog: the pages describing the models avail-able within a product category may present one or more

Figure 3: Creation of a comparison table.

items, depending on the user’s receptivity: if the sys-tem assumes that the user is confused when too muchinformation is provided in the same page, it describesonly one model per page, as in Figure 2; otherwise, itcan list two or three models per page.

The description of the features of the items is tailoredto the contents of the user model (Ardissono & Goy1999): when the system plans the content of a page, itexploits a set of personalization rules to:

¯ rate the relevance of (all) the information items thatcould be presented, on the basis of the user’s interestsand of the intrinsic importance of the features to thedescription of the item;

¯ select the amount of information to be included inthe page, depending on the user’s receptivity;

¯ choose the appropriate complexity level for the de-scriptions, on the basis of the user’s domain exper-tise. Different levels can be used, to produce tech-nical descriptions, or simple ones where the featuresare presented in an intuitive way;

¯ refine the layout of the features, choosing special sizesand styles (e.g., the boldface), depending on the rat-ings of the features.

The system selects the data to be included in the pre-sentations, as well as the appropriate description style,from a database which contains the whole informationabout the items. These decisions are made at the gran-ularity level of the single product feature, so that sig-nificantly different descriptions may be produced whenpresenting the same product to different users. Forinstance, the page shown in Figure 2 is tailored to auser characterized by a medium domain expertise; thepage contains intermediate descriptions of the features,where some technical terms are included, but are ex-plained to the user. Other descriptions would be pro-duced for different users. For instance, consider thedescription of the "polling" feature: in Figure 2, thefeature is mentioned and briefly explained. The de-scription generated for a non-expert user would be sim-

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Figure 4: A comparison table created during the interaction with our system.

pier and would contain a full explanation of the feature.On the other side, a description generated for an expertuser would be more compact and would not contain anyexplanation of the technical terms.

In addition to the development of personalizationstrategies for the generation of pages tailored to theuser, we have enhanced the opportunities for the cus-tomer to explicitly request personalized informationabout the goods. One interesting form of user-drivencustomization is the creation of the comparison tables"on the fly". When the user clicks on the related but-ton (see Figure 2), the system displays a window forthe selection of the items and the features to be com-pared. An example of this window, referring to fax-phones with answering machine, is shown in Figure 3,where the user’s selections are highlighted. When theuser clicks on the "Show compare table" button, thesystem creates the new table and displays it; Figure 4shows the table resulting from the user’s selections re-ported in Figure 3. This mechanism greatly improvesthe system flexibility, since the user is not forced toinspect large precompiled tables, but she can ask thesystem to compare only those items and features she isreally interested in.

ConclusionsThe issue of tailoring the description of goods to theneeds and capabilities of the user has been initiallyrecognized in the dynamic hypermedia research area,where many adaptive systems have been developed forthe personalized presentation of information; e.g., see(Chin et al. 1994; Jameson et al. 1995; Brusilovsky,Schwartz, & Weber 1996; Popp & LSdel 1996; Stra-chan et al. 1997; Dale et al. 1998; Milosavljevic &Oberlander 1998; Petrelli, Angeli, & Convertino 1999;A. Nill & Kobsa To appear). However, the great expan-sion of electronic commerce on the Web has highlightedthe importance of personalization issues, such as tailor-ing the suggestion and the presentation of products tothe individual customers, in virtual stores and recom-mender systems on the Web, as well.

In this paper, we have described SETA, a prototypetoolkit for the construction of adaptive Web stores thatassist the user by adapting the interaction and the sug-gestion of goods to her preferences. The personalization

of the interaction is obtained by exploiting user mod-eling and knowledge representation techniques, whichmake it possible tailoring the description of the prod-ucts to the user’s interests and domain expertise. Inthis way, personalized Web catalogs can be displayed,on the basis of the peculiarities of the individual cus-tomer.

We have tested our prototype tuning it on the basisof the suggestions collected from about 100 users, repre-sentative of different user categories, such as psycholo-gists, computer scientists, and people coming from theeconomic, administration, and humanities areas. Al-though a field-trial would be necessary to test the sys-tem in a complete way, the contribution of these peoplehas been very valuable in helping us to improve the in-terface offered by SETA, as well as its interaction style.In particular, we have realized that there is a trade-offbetween the system’s degree of initiative in the person-alization of the interaction and the need to respect theuser’s freedom during the visit of the Web store: unlikeother applications (e.g., ITS), the role of an electroniccommerce system is, in our view, helping the user to ob-tain the information she needs in a smooth way, withoutoverhelming her; for instance, the system should makethe catalog clearer and more understandable, avoidinguseless paths to the user. Moreover, the system shouldoffer the user a way to control the interaction in an ex-plicit way, in order to correct the system, when it failsto recognize her real preferences and needs. To thisextent, we are currently extending SETA, on one side,with more powerful user modeling and personalizationtechniques and, on the other side, with new function-alities which the user can exploit to request specific in-formation, or even to change the interaction style. Forinstance, the generation of pages presenting the func-tionalities offered by the various product categories isan important way to help the user in the navigation ofthe catalog: in fact, it represents a way for the userto decide whether she is interested in a certain productbefore reading the specific features of the items in de-tail. Moreover, the creation of comparison tables "onthe fly" is a way to let the user personalized a subsetof the catalog, by selecting the information about itemsthat she really wants to consider.

Although our main activity is focused on the proto-

type presenting telecommunication products, we haveenhanced the functionalities of the system by exploit-ing the gained experience in the development of otherprototypes, based on the same architecture. This workhas given us a useful feedback for the improvement ofthe adaptivity of the SETA system; for instance, ourprototype for the personalized delivery of news on theWeb has helped us to extend the personalization strate-gies, tuning them to the peculiarities of a different typeof application. More information about the personal-ized news server can be found in (Ardissono, Console,& Torre 1999) and on another paper included in theworking notes of this symposium.

Technical detailsSETA (Ardissono et al. 1999b; 1999a) is a multiagentsystem including a Web store shell and the tools whichcan be used to create a new, adaptive Web store pre-senting products in a specific sales domain. SETA isimplemented in Java, uses the Apache Web server tocommunicate with the Web, and Objectspace Voyager(Objetcspace) to create and distribute the agents of thesystem and to support communication among them. Anon-line demo of our system is available at the URL:http://www.di.unito.it/~ seta.

AcknowledgmentsThis work has been developed in the project ServiziTelematici Adattativi (http://www.di.unito.it/~ seta),carried on at the Dipartimento di Informatica of theUniversity of Torino within the national initiativeCantieri Multimediali, sponsored by Telecom Italia. Weare grateful to L. Console, L. Lesmo, C. Simone and P.Torasso for having contributed to this work with sug-gestions and fruitful discussions.

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