Quality Attributes of Web Software Applications – Jeff Offutt By Julia Erdman SE 510 October 8, 2003

Old time World Wide Web Originally designed to present information in text documents Simple framework Became complex very quickly

Modern World Wide Web Large-scale software applications for: E-commerce Information distribution Entertainment Collaborative working Surveys etc.

Modern World Wide Web cont. Diverse Run on distributed hardware platforms and heterogeneous computer systems Multiple programming languages and styles Incorporates much reuse and third party components Cutting edge technologies Must interface with users, other websites, and databases

Diversity Diverse distribution and communication Diverse components Interpreted scripting languages Plain HTML files Mixture of HTML with: Programs Databases Graphical images Complex user interfaces

Creating a Website Engineering an effective website requires large teams with diverse skills Programmers Graphics designers Usability engineers Information layout specialists Data communications & network experts Database administrators This results in Engineering a Website rather than just creating a website

Web Software Unique aspects Economic changes Criteria for success Technology changes

Unique aspects of Web application software Diverse components Need to know how to integrate the diverse components Integrated differently from regular software applications Source is often times not available Executables may be on remote machine Data transfer can occur from remote sources

Economic Changes Quality of attributes No financial motivation for quality “shrink wrap vendors” Poor quality sooner than high quality later Now must satisfy customer needs Later but better

Criteria for Success Reliability Usability Security And also, Availability Scalability Maintainability Time to Market

Reliability Users expect web applications to work There’s always another one out there

Usability Easy Little site loyalty

Security Must avoid a breach of a company’s website Secure, secure, secure

Availability 24/7/365 Downtime is costly Diverse browsers

Scalability Increase number of users Increase number of services Small weakness are exemplified Reliability problems Usability problems Security breaches

Maintainability Frequent maintenance cycles Compatibility Reluctant to fix faults before release

Time to Market Important, but not as significant with Web software applications

ALL of these attributes have become important to web software

Technology Changes First generation Web sites Client-server model Static HTML files

Client-server model

Technology Changes Growth Commercial use Full-fledged market channel for e- commerce Interactive, highly functional systems

Early Internet Client-server model Support only small websites Little security Cannot support much traffic Limited functionality

Modern Internet Fully functional software systems Instead of Webmaster, a diverse team lead by a Web manager is needed Third-party software components and middleware Two-tier model not sufficient

N-tier Model

Modern Internet cont. N-tier model Client-server connection still Most of the software now resides on separate computers rather than the web server Client -> web server -> application servers -> database server

Benefits of N-tier Model New languages are easier to modify and permit more reuse Enhances maintainability, reliability, and scalability Additional security layers

Questions???

Works Cited Offutt, Jeff. "Quality Attributes of Web Software Applications", IEEE Software, Volume 19, Issue 2, Mar/Apr 2002, pp