EL PAPEL DE LA EDUCACIÓN EN LAS POLÍTICAS DE INTEGRACIÓN

adPASS [SH04, HS03] is a system for spreading digital advertisements (ads) among interested users. Each user specifies his interests in a profile that is stored on the mobile device. The communication scheme resembles the way information is spread by word of mouth between human beings, e.g., when recommending something to someone else.

As an incentive for users to take part in the system, adPASS provides an anony- mous bonus point model that rewards a user who carries an advertisement on the way from the vendor to a potential customer.

Ranganathan and Campbell [RC02] discuss mobile advertising in pervasive environments and outline several challenges. Here, adPASS contributes in two ways: First, it is an example for serendipitous advertising and second, adPASS provides means to deliver advertisements to the right people without harming their privacy.

An introduction to adPASS was given in Chapter 3. The adPASS incentive scheme was described in detail in Section 5.2. This section provides some technical details on the adPASS prototype, its provided functionality from a user’s point of view, as well as a typical usage scenario.

Technical Details The adPASS prototype is divided into several software pack- ages that implement different roles, namely the Information Producer, Informa- tion Bearer and Information Consumer, as described in the last chapter (see Sec- tion 5.2.1), and the Mediator. All implementation was done in the Java programming language. The runtime environment for the Information Producer and Mediator is the standard Java2 Virtual Machine (VM) [Sun06] and for a Information Bearer/- Consumer a Java2 Micro Edition VM [Neg06] with its restricted capabilities. For all wireless communication, 802.11b WiFi is used in ad-hoc network mode.

For the concrete experiments, the Information Producer, acting as an Information Sprinkler, runs on a PC with Windows XP as the underlying operating system. The same holds for the Mediator. For the mobile nodes, iPAQ PDAs (Vendor Compaq, Model 3870) were used. These devices only offer limited resources: their Processor is an Intel SA-1110 (206 MHz) and the available memory is 64 MB (RAM). The iPAQ operates under Windows CE Version 3.0.

Functionality Figure 6.1 shows a screenshot of the adPASS producer, in our case a shop that offers several consumer media products (CDs, DVDs, Books,) and home entertainment hardware.

6.1 PROTOTYPES 99

Figure 6.1: adPASS Information Producer (shop) screenshot

• Creation and deletion of advertisements (Offered Ads tab in Figure 6.1). • Acceptance of handed in advertisements (Handed in Ads tab in Figure 6.1). During advertisement creation, the producer sets the product name, associated product category, price, validity period, and the amount of bonus points he is willing to issue in total on a successful purchase of the advertised product.

A consumer’s ad that is handed in during a purchase will show up in the Handed in Adstab. If the Information Producer accepts the ad, i.e., the ad is valid and was issued by him, the bearer chain is submitted to the Mediator (see protocol details in Chapter 5.2.9) and bonus points can be redeemed later by Information Bearers.

Figure 6.2 shows screenshots of the adPASS mobile node. The application GUI is organized into four tabs. The first tab (Figure 6.2(a)) allows a user to express his interest in a certain product category. The node will collect (and pass along) all advertisements that belong to the selected categories. The second tab opens an overview of already received ads (Figure 6.2(b)). A user may view details of the ad to see whether the ad is useful. With the Use-button, a user hands in the ad at a shop. The Statistic-tab displays information about the amount of bonus points gained for later use and a report on the key generation and usage process. Recall from Chapter 5.1 that a user stays anonymous by generating a set of public keys as aliases. Our prototype always keeps a minimum of 6 key pairs at hand, which can be configured at program startup. Whenever the application is idle, the key generation process is triggered. With the fourth tab (Figure 6.2(d)), a user specifies the minimum amount of bonus points left in an advertisement to be of interest for him and the maximum amount of bonus points he is going to claim for himself (set to 4 points in the screenshot).

Typical Usage Scenario The ideas behind adPASS were already discussed on page 50. The roles and interaction pattern have been described in detail in Sec-

(a) Interests tab (b) Received Ads tab

(c) Statistic tab (d) Setup tab

6.1 PROTOTYPES 101

tion 5.2. For the sake of readability, we will briefly recapitulate major points now. A typical usage scenario comprises the following steps:

1. An Information Producer (here an owner of a shop) generates advertise- ments for dissemination via adPASS. Information Sprinklers broadcast these advertisements within the vicinity of a shop.

2. A mobile node in communication range of an Information Sprinkler copies ads it is interested in on to the device. The node claims a certain amount of bonus points that come with the ad. The ad is then passed on to other users by serendipity encounters with other nodes. This leads to the construction of the bearer chain.

3. A user that makes use of the ad and buys the advertised product visits the shop. At the same time, the bearer chain is given to the shop and in turn passed on to the Mediator.

4. adPASS participants periodically query the Mediator for successful advertise- ment propagation that lead to a bonus point reward. These payouts are used later by the participants.

The adPASS prototype is used mainly to evaluate our proposed privacy preserving scheme (see Section 6.3), since the need for privacy preservation is crucial in opportunistic network applications of this type.