Molde University College INF 245 Fall 2007 OBø 1 INF245 Application Architectures H 2007 Ola Bø

Molde University College INF 245 Fall 2007 OBø 2 Architectures Four main architectures Wireless internet aka thin clients Smart clients Message based Ultra thin architecture – terminal clients Architecture is important How to choose the right architecture? What are strong and weak properties for each architecture? The purpose of this lecture is to answer the two questions above.

Molde University College INF 245 Fall 2007 OBø 3 Factors that determine the choice of architecture Target users: who, technical skill, scenarios for use Mobile devices: Is there an installed base or can we select devices for the job? – if so what is the most appropriate device Connectivity: How to connect. Is wireless necessary. What kind of wireless. Data quantity vs. connection Data: Quantity. Where is the data, can it be downloaded at the spot or do they have to exist in the device. How volatile is the data, local vs. central data? Integration: How to access other systems. Are they available over the Internet? Security: Is the information sensitive. How can the information be stored on and transferred to and from the device in a secure way. Is the local data store secure against break-ins. What about authentication, viruses. What if the device gets stolen? Battery time. Is it a problem. What about consumption for wireless, charging during the workday, backup batteries?

Molde University College INF 245 Fall 2007 OBø 4 Application architectures Terminal Client?

Molde University College INF 245 Fall 2007 OBø 5 Applications based on wireless web Gate way Uses different markup languages WML cHTML XHTML Some browsers can prestore internet pages. (web clipping) Can deliver content in different markup languages WML cHTML XHTML

Molde University College INF 245 Fall 2007 OBø 6 Architectures built upon wireless www advantages Easy to install on the device an extension of existing Internet applications User Interface is well known – no extra training Simple integration with other applications using Internet Available on many mobile devices Data always up-to-date Security disadvantages Wireless access is essential Bad performance due to latency time and bandwidth limitations Security Communications cost Still rudimentary browsers No scripting? no ajax? weak CSS support? Primitive user interface Considerable browser heterogeneity Testing difficult Discussion: Will disadvantages decrease in the near future?

Molde University College INF 245 Fall 2007 OBø 7 Applications built upon wireless Internet Here are some applications best implemented using wireless internet Stock trading Information services News, weather, sport M business

Molde University College INF 245 Fall 2007 OBø 8 Smart client architecture Devices may store data locally May work without a wireless connection Updating is called synchron- isation The smart client may be developed by using either the J2ME platform or by using the device operating system as a platform. Provisioning is a problem? A synchronisation server is responsible for same information in the central and mobile databases.

Molde University College INF 245 Fall 2007 OBø 9 Advantages and disadvantages of smart clients Advantages may work locally without connection data is always available rich user interface better performance distributed computing security lower communication costs better autonomy Disadvantages More difficult integration More difficult provisioning More difficult maintenance Complex development for heterogeneous platforms Security

Molde University College INF 245 Fall 2007 OBø 10 Applications for smart clients Smart clients should be considered when Wireless connection is not available or has too low bandwidth We need a more advanced user interface for example for gaming We must use resources not available from a thin client: GPS, Camera, RFID-reader We can save data transfer time and cost The application is free- standing Samples Sales Force Automation – essential to have data present when meeting customer Field Force Automation- Support for service technicians Information and task Health-service Data collection services inventory surveys

Molde University College INF 245 Fall 2007 OBø 11 Message based architecture Many possible messaging technologies User to user , sms, im, mms  Can also be generated by servers Alerts and alarms WAP push, sms Application to application The device must have a smart client using messaging to communicate Message Queue Properties of message-based architectures Messages that can not be forwarded are stored Stored messages will be sent when possible Can be combined with other architectures

Molde University College INF 245 Fall 2007 OBø 12 Message based application to application architecture

Molde University College INF 245 Fall 2007 OBø 13 Advantages and disadvantages of message based applications Advantages: Message handling is preinstalled and most users are familiar with it. Messages are pushed Can fill in missing two- ways communication in pull based architectures Store and forward robust when bad wireless coverage Many technologies to choose from Disadvantages User has weak support when entering messages (no form or labels) Syntax must be simple Only simple interaction is possible Application to application messaging may be complicated

Molde University College INF 245 Fall 2007 OBø 14 Message based applications Popular in consumer-applications Communication Entertainment Information dissemination Business applications Efficient for information exchange Asynchronous Extension of existing apps Alarms if certain events

Molde University College INF 245 Fall 2007 OBø 15 Mobile applications may benefit by combining with desktop Some use cases fit better to a desktop workstation Is a workstation available? Some of the use may be done on a workstation Order airplane tickets Manage appointments Find the auction Get an overview of the inventory Touch up images Some use cases may be done on the mobile unit Is the plane delayed? Check address for next appointment and find the way Get information about the last bid and enter a new bid Count inventory Take picture The common pattern is using the desktop when you need an overview over large amounts of data using a good user interface. The mobile is used to handle smaller amounts of information in a mobile context. The same application may be used on both.

Molde University College INF 245 Fall 2007 OBø 16 How to exchange data between workstation and mobile device Synchronization Data are updated on stationary and mobile automatically according to rules File transfer Data are transferred using object exchange via BT or IR Both units are using the same server, site or database If a smart client has a local database, the databases may be synchronized.

Molde University College INF 245 Fall 2007 OBø 17 Solutions based upon terminal client and terminal server A terminal client transmits all input to server and displays visual output from the server A terminal server runs many user sessions interpreting input and generating screen output This can be done with surprisingly low bandwidth Can be developed as an ordinary desktop app, but using limited IO The terminal server has full connectivity May continue session after communications break But no communications => no application

Molde University College INF 245 Fall 2007 OBø 18 TC/TS Solutions pros and cons Advantages Easy installation? Easy upgrades Don’t need to learn a new environment No browser heterogeneity Powerful platform No need for software to handle communications breakdown User reconnects to the same session No extra database complexity Disadvantages Wireless access is essential Terminal client must be installed Screen size must be standardized and not too small No access to device resources? Communications cost IO different from platform IO

Molde University College INF 245 Fall 2007 OBø 19 Exercise The maintenance workers of a manufacturing company are servicing machines in production facilities in a number of sites within a large area. For each service job there is an there is an operating procedure and possibly drawings of the equipment to be serviced. The part inventory database and the log for service jobs should also be available and updatable. The service jobs are done regularly on a weekly to yearly schedule. The maintenance is done partly in places that are difficult to access demanding climbing ladders or passing through narrow openings. It is an advantage if the mobile equipment is available when the work is being carried out. The workers also need to communicate with each others and with the maintenance managers. Some of the work places ar without GSM or WLAN coverage. Exercise: Suggest use cases, application architecture, and what wireless network and what kind of mobile devices may be sutable for an application supporting the activities described

Molde University College INF 245 Fall 2007 OBø 20 Exercise You are working with an application to support ornithologists. The main goal of the application is to enable registration of birds in an area. The date being registered are species, number of adults, number of eggs/offspring, date, time and comment. The registered information shall be transferred to a central data base. In rare cases, the ornithologist is in doubt as to which species he is observing. Therefore images and sounds for all species should be available on the mobile device. Some of the areas being observed are outside the coverage area of mobile networks. Exercise: Suggest use cases, application architecture, and what wireless network and what kind of mobile devices may be sutable for an application supporting the activities described

Molde University College INF 245 Fall 2007 OBø 21 Exercise After testing opinion using a questionnaire there is a substantial amount of supplementary work punching the questionnaires into the database of results. The cost and number of errors committed can be reduced by registering the answer directly into a database while the respondent is answering. Your job is to plan a mobile application that is practical for the employees of the opinion surveying agency when the surveying is being done by walking from door to door in an area or by stopping people in the street. Suggest use cases, application architecture, and what wireless network and what kind of mobile devices may be sutable for an application supporting the activities described

Molde University College INF 245 Fall 2007 OBø 22 Exercise Petrine’s Pizza wants to make it possible for customers to order pizzas from mobile devices. The customer should receive response confirming that the order has been received and telling when the pizzas will be delivered. Discuss the pros and cons of implementing this as an sms-service versus as a thin client solution. Why are smart clients inappropriate for this application?