Chapter 8 Flashcards
What are the Client/Server architectures?
- Networked computing model
- Processes distributed between clients and servers
- Client-Workstation (PC, smartphone, tablet) that requests and uses a service
- Server - Powerful computer (PC/mini/mainframe) that provides a service
- For DBMS, server is a database server
- For the Internet, server is a web server
What are the three application logics in Client/Server systems?
- Presentation Logic
- Processing Logic
- Storage Logic
What are the components of Presentation Logic?
- Input - Keyboard/mouse
Output - Montior/Printer
* This is the GUI Interface *
What are the components of Processing Logic?
- I/O processing
- Business Rules
- Data Management
* These are Procedures, functions, and programs *
What are the components of Storage Logic?
- Data storage/retrieval
*This is DBMS activities*
What is application partitioning?
- Placing portions of the application code in different locations (client vs. server) after it is written.
What are the advatages of application partitioning?
- Improved performance
- Improved interoperability
- Balanced workloads
Two-tier client-server environments example
Where can processing logic be in a two-tier client-server environment?
- Client (Fat client)
- Server (thin client)
- Both (distributed environment
Three-tier and n-tier client-server environments example
Where is the processing logic in a three-tier and n-tier client server environment?
- At the application server or Web server
In a two-tier database server architectures what is the Client worksation responsible for?
- Presentation logic
- Data processing logic
- Business rules logic
What does the server perform in a two-tier database server architecture?
All data storage, access, and processing.
- Typically called a database server
*DBMS is only a server*
Database server architecture (two-tier architecture) example
What are the characteristics of two-tier client/server systems?
- Departmental in scope (few users)
- Not mission-critical
- Low transaction volumes
- Common programming languages are Java, VB .NET, C#
- Interface database via middleware, APIs
What is middleware?
Software that allows an application to interoperate with other software without requiring user to understand and code low-level operations
What is an Application Program Interface (API)?
Routines that an application uses to direct the performance of procedures by the computer’s operating system.
What are the common database APIs?
ODBC, ADO .NET, JDBC
What are the steps for using databases via middleware APIs?
- Identify and register a database driver.
- Open a connection to a database.
- Execute a query against the database.
- Process the results of the query.
- Repeat steps 3-4 as necessary.
- Close the connection to the database.
What are the components of a three-tier architecture?
- Client - (GUI interface (I/O processing)) - Browser or Mobile App to access
- Application server - (Business Rules) - Web Server
Database Server - Data storage - DBMS
What is a Thin Client?
- PC just for user interface and a little application processing. Limited or no data storage (sometimes no hard drive)
Generic three-tier architecture example
What is a thin client?
An application where the client accessing the application primarily provides the user interfaces and some application processing, usually with no or limited local data storage.
What is a thin client application?
A web browser and the 3-tier architecture involves a Web application.
A database-enabled intranet/Internet environment example
What are the components of a web application?
- Database Server
- Web Server
- Application server
- Web browser
What is the purpose of the database server in a web application?
It hosts the DBMS
example: Oracle, SQL Server, Informix, MS Access, MySql
What is the purpose of the web server in a web application?
It receives and responds to browser requests using HTTP protocol
example: Apache, Internet Information Services (IIS)
What is the purpose of the applicatino server in a web application?
The software buidling blocks for creating dynamic web sites
example: MS ASP .NET framework, Java EE, ColdFusion, PHP
What is the purpose of the Web browser in a web application?
Client programs that sends web requests and receives web pages
example: Internet Explorer, Firefox, Safari, Google Chrome
What programming languages are used for creating web pages?
- Hypertext Markup Language (HTML) - markup language specific for web pages
- Standard Generalized Markup Language (SGML) - markup language standard
- Extensible Markup Language (XML) - markup language allowing customized tags
- XHTML - XML-compliant extension of HTML
- JavaScript/VBScript - scripting languages that enable interactivity in HTML documents
- XSL and XSLT - XMS style sheet and transformation to HTML
What are static page requests?
.htm or .html requests handled by the Web Server
What are dynamic page requests?
- .jsp, .aspx, and .php requests are routed to the application server
- Server-side processing by JSP servlet (Java), ASP .NET application (C# or VB), ColdFusion, or PHP
- Database access via JDBC, ADO .NET, or other database middleware
Example of information flow in a three-tier architecture
What are considerations in 3-tier applications?
- Stored Procedures - Code logic embedded in DBMS; Improve performance, but propriertary.
- Transactions - Involve many database updates; Either all must succeed, or none should occur.
- Database connections - Maintaining an open connection is resource-intensive; Use of connection pooling
What are the advantages of stored procedures?
- Performance improves for compiled SQL statements
- Reduced network traffic
- Improved security
- Improved data integrity
- Thinner clients
What are some of the disadvantages of Stored procedures?
- Programming takes more time
- Proprietary, so algorithms are not portable
What are the benefits of three-tier architectures?
- Scalability
- Technological flexibility
- Long-term cost reduction
- Better match of systems to business needs
- Improved customer service
- Competetive advantage
- Reduced risk
What is cloud computing?
A model for creating ubiquitous, convenient, on-demand access to network services.
What are the characteristics of cloud computing?
- On-demand
- Broad network access
- Resource pooling
- Rapid elasticity
- Measured service
What are the types of cloud computing?
- Infrastucture-as-a-service (IaaS)
- Platform-as-a-service (PaaS)
- Software-as-a-Service (SaaS)
What is Extensible Markup Language (XML)?
A text based markup language (like HTML)
- It uses elements, tags, attributes
- It includes document type declarations (DTDs), XML schemas, comments, and entity references
What revolutionizes the way data is exchanged over the Internet?
XML (Extensible Markup Language)
What are four common options for storing XML documents?
- Store XML data in a relational database by shredding the XML document
- Store entire XML document in a large field (BLOB or CLOB)
- Store the XML document using special XML columns
- Store the XML document using a native XML database (non-relational)
What does XPath do?
One of a set of XML technologies supporting XQuery development, locating data in XML documents
What is XQuery?
An XML transformation language that allows applications to query both relational databases and XML data
What is Extensible Stylesheet Language Transformation (XSLT)?
A language used to transform complex XML documents and also used to create HTML pages from XML documents.
What can translate a single XML document into both standard HTML and WAP/WML for cell phones without the necessity for two different pages?
Extensible Stylesheet Language Transformation (XSLT)
What is a set of emerging XML-based standards that define protocols for automatic communication between software programs over the web?
Web Services
What is a standard for creating a distributed registry of Web services?
Universal Description, Discovery, and Integration (UDDI)
What is an XML-based grammar for describing a Web Service and specifying its public interface?
Web Services Description Language (WSDL)
What is an XML-based communication protocol for sending messages between applications over the Internet?
Simple Object Access Protocol (SOAP)
Web Service protocol stack example
What is service oriented architecture (SOA)?
A collection of services that communicate with each other, usually by passing data or coordinating a business activity.
What is a new paradigm for IT application development, based mostly on Web service?
Service Oriented Architecture (SOA)
What are the benefits of Service Oriented Architecture (SOA)?
- Loosely coupled, highly interoperable components
- Leads to flexibility and shorter development time
