GAP: A Tool to Solve the Problem of the Web Contents Visualization in

Pocket PC Devices.

J. Carlos Olivares R., J. Gabriel González S., Azucena Montes R., Víctor J. Sosa S. e I. Rafael

Ponce M.

Centro Nacional de Investigación y Desarrollo Tecnológico(cenidet)

Cuernavaca, Morelos, México

{jcolivares04c, gabriel, amr, vjsosa, rafaxzero4c}@cenidet.edu.mx

Abstract

This tool intends to fill the existing ‘GAP’ in the

Web sites visualization in mobile devices, such as

Pocket PC. In order to guarantee that the users can

correctly visualize the Web resources, two things are

needed: a mechanism for controlling disconnections,

and allowing visualization of Web content despite of

the device connection state (hoarding), and a

mechanism that can adapt the Web content to the

specific mobile device features (transcoding). GAP is a

tool that integrates these two mechanisms and allows

improving of the user’s navigation experience in the

Mobile Web.

Keywords: Pocket PC, Visualization, Web Resources,

Hoarding, Transcoding.

1. Introduction

Mobile devices are each time closer in time,

according with [1]: "By 2009, more than a half of the

microprocessors made in the world will be intended for

mobile devices." "The software that will really make

mobile devices useful isn’t developed yet." These

statistics reflect that the use of mobile devices is

increasing due to their tiny size and that its power of

processing and versatility is growing day by day.

The problem of Web resources visualization in

mobile devices is the fact that the great majority of

Web sites in Internet have not been designed for this

type of devices. The mobile devices have limited

resources like small screens, little memory, low

processing speeds, etc; in comparison with traditional

computers equipment.

On other hand, the Web and the protocol that

manages it: HTTP are connection oriented (they are

based on TCP) what causes the transaction to fail if

the user, by any reason, becomes disconnected from

the network . In this case, it might not be possible to

visualize the Web resources in the mobile client.

Disconnections are frequent in this type of devices,

mainly because of their main advantage: mobility.

In this work a system which development is in

progress is described. It focuses in attacking the

problem of Web resources visualization on mobile

devices. The main characteristic of this work is that

great part of the system is executed in this kind of

devices, in comparison to the great majority of the

existing solutions that are executed in traditional

platforms.

2. Alternatives of solution

In order to solve this problem several alternatives

are presented: to design a new protocol, to modify and

existed protocol or to implement intermediary services

that solve the problem.

2.1 New protocols

In this scheme is possible to mention the WAP

protocol and the WML language, they work in an

analogous way as HTTP-HTML in the traditional Web.

The problem strives in that WAP only works with

mobile equipment and this would bring the same

fragmentation that today has the Web (special pages

for all class of devices). In addition, WAP was

originally designed for devices with limited resources

capacities (monochrome screens, lower bandwidth, etc)

which is actually solving day by bay through

bandwidth wireless connection (WCDMA, UTMS,

802.11g, WiMax, etc) and with more and more

powerful equipment.

The best solution would be to create a new protocol.

The problem is that this one must be totally compatible

with the existing ones, because if not, it would let

unusable thousands of existing resources (it would be

necessary to modify as much Web servers as Web

clients).

2.2 Modification of protocols

Within this alternative exits the case of having a

new request scheme of Web resources. This new

scheme receives the name of Push, whereas traditional

scheme receives the name of Pull [2].

The Pull scheme receives the name of “over

demand’. Under this scheme, the client (user) is who

visualizes a resource in an explicit way. In our case, if

a user wants to see the page of cenidet, must write in

the Web browser the next URL:

http://www.cenidet.edu.mx/.

The Push scheme also receives the name of

'subscription-notification'. In this scheme, the user

subscribes itself to a service and when some event of

interest happens a notification is sent for alerting the

user about the event.

Generally these two schemes do not live on isolated

way. Hybrid schemes (Pull&Push) have been applied

in diverse existing services, so is the case of the

reception of SMS/MMS messages, where the send of

messages is Pull and the reception is Push, since it

notifies to users about the existence of new messages.

Another service that has made famous devices like

the Blackberry to become successful is the Push-mail

[3]. This service comes to solve the problem of email

visualization in mobile environments. Under the

traditional scheme of the electronic mail, for consulting

the email, a user must be connected all the time to

receive it. This originates great costs if the network

connection generates costs per time. With this new

scheme, the user is not connected to the mail server.

When a new mail in the server is received, it notifies

the client of the existence of the new mail and sends it

to the mobile client.

For this type of schemes, protocols like HTTPU

(HTTP over UDP) or HTTPMU (HTTP over multicast

UDP) have been proposed, and basically works similar

to the HTTP but using datagrams, which are not in an

oriented connection way. With these protocols are

possible to offer a better quality in the mobile Web [4].

2.3 Intermediary services

This is the more extended solution to solve the

problem of Web resources visualization and many

other problems present on Web, like the case of

firewalls that solve some of the Web security problems

like the access control, or proxies’ caches that tries to

reduce the access latency to the information.

The scheme of intermediaries is widely used

because it doesn’t need to modify neither the clients

nor the servers; in fact, the client and server processes

do not notice the existence of these intermediary

services. These services are in charge of the hard work

and are transparent to the users.

The tool that is described in this article, works

under the scheme of intermediary services.

3. Proposal of solution

The hoarding process solves the problem of Web

resources visualization without concerning the state of

the connection of the mobile device. For this, it

becomes necessary that the user has already stored, in

local way, in his device the resources that he o she will

use.

As can be observed, the amount of resources to

occupy can be immense, whereas the capacity of

storage of the devices is limited. In order to give

solution against this new problem is necessary to have

an effective way to know the resources that a user

could use. With hoarding is possible to reduce this,

through algorithms of association rules applied on Web

logs, is determined the optimal set of resources that

will be replicated to the mobile clients [5].

A mechanism which tries to solve the adaptation

problem of Web resources to the displaying capacities

on mobile devices is transcoding. It consists of

transformation of resources, distilling and processing

of all those characteristics that are not available in the

device is needed. The used mechanism of transcoding

uses HTML to a subgroup of HTML transformer,

using XML.

The system is based on client-server architecture

with an intermediate tier on the server side as on the

client side. The system is shown in Figure 1.

Figure 1. General architecture proposed.

The general system has been denominated GASWT

(Gestor de Acaparamiento de Sitios Web

Transcodificados: Hoarding Manager of Transcoding

Web Sites). The intermediary in the client side is

denominated GAP (Gestor de Acaparamiento para

Pocket PC: Hoarding Manager for Pocket PC),

whereas the server side is denominated GAT (Gestor

de Acaparamiento y Transcodificación, Hoarding

Manager and Transcoding). The GAT is composed by

MA (Mecanismo Acaparador: Hoarding Mechanism)

and by MT (Mecanismo Transformador: Transcoding

Mechanism). The communication between the

processes is made through a HTTP request-response

scheme.

As much the MA as TM are taken from other

projects that together with this one, comprise the

Moviware project [6], whose main function is to offer

a set of services to mobile clients that have frequent

disconnections.

The general operation of the system is described in

the next lines. The user introduces an URL from the

Web browser (which has been previously configured to

redirect his exit towards the GAP). The GAP receives

the request and determines if it is in the local cache of

the device, if found, the hoarded resource is sends to

the Web browser.

When the resource is not hoarded, the system

validates the connection existence in order to obtain

the resource on line. If for some reason the resource

cannot be shown, (because it doesn’t exist or has

detected an error in the connection) the system notifies

the user by sending an error message.

On the other hand, if the Web resource is not

hoarded and a pattern of the site in the local device

doesn’t exist, the MA sends the Web resources if a

pattern for this site exists. If the pattern exists but the

hoarded resources in the MA aren’t present, it obtains

them by requesting them to MT and soon compresses

the resources in zip format to optimize the process.

Once the MA has sent the hoarded Web site, the

mobile device must decompress the Web site and

update its list of patterns. This process happens in

transparent way, in a way that the user never notices.

MT is responsible of collecting documents and if

they are HTML, it transforms them if the configuration

parameters indicate that. The transcoding is made on

line, because the process is slowed down if the

document is too large.

The actions that the user can make on the system

consist in visualizing Web sites on line, visualizing

Web sites on disconnection mode, visualizing error

messages, visualization of the requests states and

finally, set up the system.

The GAP is basically conformed of three main

modules which are: Observer, GAL (Gestor de

Acaparamiento Local: Local Hoarding Manager) and

GDL (Gestor de Desconexión Local: Manager of Local

Disconnection).

The Observer is responsible of processing each

request and to give back the result to the navigator.

The GAL is responsible of the manipulation and

control of the cache in the device. The users decide

which resources are susceptible of hoarding, as well as

limiting the storage space.

The GDL is responsible of determining the state of

the connection. The control of the disconnections has

been used drilling the network during three seconds.

Observing the quality of the results, a threshold of 30%

of accepted connections determines if the client is

connected (if the threshold is surpassed or equaled) or

is on disconnection mode (if it is below the threshold)

[7].

For the implementation of this tool, we used .NET

Compact Framework 1.0 with C # language, because it

is the best option to program in Pocket PC platform

[8].

The modifications of the MA and MT are being

made in Java so that it is language in which these

modules are programmed.

4. Results

The tool described in the present document has been

proven in diverse equipment like Pocket PC 2000

(Compaq iPAQ H3630), Pocket PC 2002 (HP Jornada

5500), Pocket PC 2003 (HP rx3115), emulators of

Windows CE, desktop PC (Compaq Presario with

Pentium 4 1.4 Ghz. processor, 512 Mb of RAM

memory).

The first test scenario consisted of acceding to the

Web resources in on line mode. We obtained

satisfactory results (see Figure 2).

In the number two test scenario, the GAP was

executed without being connected to the network.

Additionally we had a pattern of a hoarded Web site

(http://www.cenidet.edu.mx/) and resources. In this

case not existing images in the original site were used,

because it was possible to verify that the hoarded

resources are correctly displayed.

The number three test scenario (see Figure 3),

demonstrates that it is possible to transcoding the

resources in the device as well as showing them in a

local way if they are hoarded and without transcoding.

It is Also possible to execute the GAP in other

platforms like Smartphones (SmartGAP) and a desktop

PC (WinGAP). GAP, WinGAP and SmartGAP are the

same program but with different name, to differentiate

the platforms in which they’re running.

5 Conclusions

With the presented tool is being demonstrated that it

is possible to execute complex services in Pocket PC

devices, so is the case of an intermediary service that it

allows to visualize Web resources when it exists or not

a network connection.

At this time we have verified in an isolated way

most of the functions of the system (it lacks the

methods of decompression of the hoarded site), it

would be necessary the respective integration of

components and testing to the system in its totality.

Figure 2. Case of test 1: Visualization of Web

resources with network connection.

Figure 3. Visualization of Web sites in

disconnection mode with hoarded Web resources

and without transcoding.

Figure 4. Case of test 3: Visualization of Web sites

in connection mode, with hoarded and transcoding

resources.

The expected benefits at the conclusion of this

investigation work are: 1) Visualization of Web sites

without mattering if the devices are connected or not.

2) Reduction of latency in the access to the

information, if the resource is hoarded locally. 3)

Energy Saving by the fact to work in disconnection

mode. 4) Saving money if the user decides not to

connect to a network that receives the service and

generates expenses by the access time. 5) Facility of

administration of Web sites when not having different

versions to each device.

6. Acknowledgments

We want to give thanks to Rocío Vargas Arroyo for

her contribution in correct this paper.

7. References [1] SG magazine, http://www.softwareguru.com.mx [visited

march 2006]

[2] Purushottam Kuikarni, et al., “Handling Client Mobility

and Intermittent Connectivity in Mobile Web Accesses”,

Department of Computer Science, University of

Massachussets.

[3] Blackberry’s push technology,

http://www.blackberry.com/products/software/integrations/p

ush_email.shtml [visited march 2006].

[4] UPnP Forum, http://www.upnp.org/, [visited march

2006]

[5] David Valenzuela, “Mecanismos para predicción de

acaparamiento de datos en sistemas clientes/servidor

móviles”, masther thesis, cenidet, august 2002.

[6] Gabriel González. “Plataforma middleware reflexiva para

aplicaciones de cómputo móvil en Internet (Movirware)”,

cenidet.

[7] J. Carlos Olivares, et al, “Control de desconexiones en la

visualización de páginas Web en dispositivos móviles

Windows CE”, for appear in XVI CIECE’06, april 5,6 and 7

2006, Cd. Obregón, Sonora, México.

[8] Gabriel González, Azucena Montes, J. Carlos Olivares,

“Comparativa y evaluación de las herramientas de

programación para desarrollar aplicaciones en plataforma

Pocket PC”. VI CICC’05, Colima, Colima, México,

september 2005.