1 Computer applications in the modern enterprise Επιχειρησιακές Εφαρμογές Η/Υ Lectures 4 and 5: Enterprise Key Technologies Univ. of the Aegean Financial and Management Engineering Dpt Petros KAVASSALIS

2 What you will learn in this course A set of fundamental concepts and frameworks for understanding the potential impact of information technology (IT) on business strategy and structure A set of fundamental concepts and frameworks for understanding the potential impact of information technology (IT) on business strategy and structure  Computers and Information Systems (IS)  The business value chain  Business integration through Enterprise Application Integration Information Systems in practice: How does the modern enterprise use “Business Intelligence” (BI) systems to improve decision-making Information Systems in practice: How does the modern enterprise use “Business Intelligence” (BI) systems to improve decision-making  Methods and BI examples  “Hands-on” experience: create business reports by using Eclpise BIRT Reporting Tool (

3 Communication tools Course web site: see FME web site Course web site: see FME web site

4 Students evaluation Class Participation (20%) Class Participation (20%)+ Assignments (20%) Assignments (20%)+ Final Exam (60%) Final Exam (60%)

What I am going to say Within the modern enterprise Within the modern enterprise  Inter-organizational relationships  Intra-organizational relationships are supported by Information Technologies are supported by Information Technologies It is about enterprise applications that inter-operate to move information around It is about enterprise applications that inter-operate to move information around  Not only within existing business frontiers but also within the network of the collaborators and customers of an enterprise  Not randomly but in an organized way, within the enterprise architecture framework 5

Enterprise architecture [I will come back later on] 6

Let’s start from the fundamentals: basic infrastructure 7 Web technologies and applications APIs Client-Server Technology Network Internet Attention: The content of this presentation is mostly based on: M. Papazoglou and P. Ribbers, e- Business: Organizational and Technical Foundations, Jon Wiley and Sons, 2006, chapter 6. Students are encouraged to read this chapter.

1. The Internet The standards by which computers (enterprise applications) communicate with each other and with remote components The standards by which computers (enterprise applications) communicate with each other and with remote components Generally speaking Generally speaking  Internet infrastructure enables various distributed applications o , Web browsing, Skypying, file sharing, online games, online forms fill up o Internet a network of interconnected networks 8

An overview of the Internet 9 Business Network Partners’ Network Subsidiary’s Network

2. Client-Server technology Computers go… network Computers go… network Centralized processing vs distributed processing Centralized processing vs distributed processing  Centralized processing: all processing in one central computer  Distributed processing: the processing work is executed by different computers, central machines (mainframes etc) and PCs linking together In a large of cases, the enterprise needs centralized data control and widespread data accessibility In a large of cases, the enterprise needs centralized data control and widespread data accessibility  Client/Server is a computational architecture with o Client processes (service consumers) o Server processes (service providers) o Where the client requests service from the server o Service example: customer dara, inventory data 10

Roles that change A client computer for an maybe a server for another application A client computer for an maybe a server for another application  The computer requests data from a central server for the available products in a inventory and publishes them over the Web (through another application, a web site application) Give an example of client you use Give an example of client you use  Google desktop 11

Basic features Clients and servers run on separate dedicated machines connected through a network Clients and servers run on separate dedicated machines connected through a network and servers are software modules with well defined interfaces and servers are software modules with well defined interfaces  I “can’t” see the function performed by a client, they “hided” behind an interface Each client/server relationship is established between 2 entities that exchange messages Each client/server relationship is established between 2 entities that exchange messages Message exchange is interactive Message exchange is interactive 12

An example Order application via the client/server model Order application via the client/server model  Order processing databases are located at the corporate office o Customer information o Product information o Billing  Stores possess clients that communicate with the central system to pass orders Result: Result:  Many order processing points  Standardization of the order processing through a common interface for everybody 13

A variation of the server/client model The client possesses extended functionality: rich or fat client The client possesses extended functionality: rich or fat client  It has its own functionality, independent of the central server  It performs most of the code that implements the use interface and the business application logic  It implements the database access mechanisms on the server-side Advantage: flexibility Advantage: flexibility  When the business application changes, no need to modify the “huge” server-side Advantage: bandwidth economies Advantage: bandwidth economies  Rich clients have advantages in multimedia-rich applications (for example video-games) that would be bandwidth intensive if fully served 14

Another variation: the three-tier architecture (1) 15 Processing Data Repositories

Another variation: the three-tier architecture (2) A middle-tier is introduced between the use system interface (client) and the database server: processing A middle-tier is introduced between the use system interface (client) and the database server: processing  Presentation-tier o GUI (Web browser)  Processing or Server-tier o Business application logic o Processing execution  Data-tier o Holds the permanent data for the application How these tiers interface each other? How these tiers interface each other?  Customized code  APIs Advantages Advantages  Improved performance for groups with a large number of users  Flexibility and scalability albeit the complexity of distributed processing 16

3. APIs Application Programming Interface Application Programming Interface  Hooks that can be used to connect to an application to invoke its business logic and retrieve its underlying data  An API is an abstraction that describes an interface for the interaction with a set of functions used by components of a software system (Wikipedia) o The software providing the functions described by an API is said to be an implementation of the API Please give examples Please give examples  API  Web API API integration is synchronous in nature and point-to-point API integration is synchronous in nature and point-to-point 17

API as enterprise property APIs can be among a company's greatest assets APIs can be among a company's greatest assets  Customers invest heavily: buying, writing, learning  Cost to stop using an API can be prohibitive  Successful public APIs capture customers Can also be among company's greatest liabilities Can also be among company's greatest liabilities  Bad APIs result in unending stream of support calls References [see Course Web Page] References [see Course Web Page] 18

API: a Wikipedia example s&bltitle=Star%20Wars&bllimit=10 s&bltitle=Star%20Wars&bllimit=10 s&bltitle=Star%20Wars&bllimit=10 s&bltitle=Star%20Wars&bllimit=10  — This is the place on the web where the API lives.  action=query — fetch the data requested in the rest of the URL  list=backlinks — list pages that link to a specific page  bltitle=Star%20Wars — the specific page with the title “Star Wars” (note that %20 represents a space)  bllimit=10 — limit to 10 results 19

API: A Twitter example girldawn girldawn girldawn girldawn  — Version 1 of the Twitter API  users — users section of the API to gather information on a user.  show.xml — display the output as XML  screen_name=geekygirldawn — the user that you want information about (geekygirldawn) 20

API: Google Maps

4. Web technologies and applications What is the web? What is the web?  Web organizes inter-linked pages of information residing on sites through the world  The Web is one of the services that runs on the Internet o A collection of interconnected documents and other resources, linked by hyperlinks and URLs, and accessed via the Internet  Result: Information can be automatically shared Web-based applications Web-based applications  Web server  Content files (Web pages)  Gateways to non-Web content (for example: databases) o Please design the architecture on the basis of the client/server model 22

Construction of Web applications 23 Non-Web content Web Gateway more