In the last twenty years, the evolution of web systems has been driven along three dimensions: the processes used to develop, evolve, maintain and re-engineer the systems themselves; the end products (the pages, content and links) of such processes; and finally the people dimension, with the extraordinary shift in how developers and users shape, interact and maintain the code and content that they put online. This paper reviews the questions that each of these dimensions has addressed in the past, and indicates which ones will need to be addressed in the future, in order for web system evolution to be sustainable. We show that the study on websites evolution has shifted from server- to client-side, focusing on better technologies and processes, and that the users becoming creators of content open several open questions, in particular the issue of credibility of the content created and the sustainability of such resources in the long term

Baravalle, A

Boldyreff, C

Capiluppi, A

Marques, R

English

Brunel University Research Archive

On the Sustainability of Web Systems EvolutionAndres BaravalleACE – University of East LondonLondon, UKa.baravalle@uel.ac.ukCornelia BoldyreffGreenwich UniversityLondon, UKc.boldyreff@gre.ac.ukAndrea Capiluppi and Renata MarquesDISC – Brunel UniversityGreater London, UKandrea.capiluppi@brunel.ac.ukremarques@gmail.comAbstract—In the last twenty years, the evolution of websystems has been driven along three dimensions: the processesused to develop, evolve, maintain and re-engineer the systemsthemselves; the end products (the pages, content and links)of such processes; and finally the people dimension, with theextraordinary shift in how developers and users shape, interactand maintain the code and content that they put online. Thispaper reviews the questions that each of these dimensions hasaddressed in the past, and indicates which ones will need to beaddressed in the future, in order for web system evolution to besustainable.We show that the study on websites evolution has shiftedfrom server- to client-side, focusing on better technologies andprocesses, and that the users becoming creators of content openseveral open questions, in particular the issue of credibility ofthe content created and the sustainability of such resources inthe long term.I. INTRODUCTIONThe study of web systems and their evolution, researchedfor many years in the WSE series and elsewhere, has grownalong three main phases: the first depended heavily on thetechnologies and infrastructures that web systems were basedupon, so servers, their performance [15] and how to optimisetheir workload [2].The second phase shifted the research from the issuesof server-based development to client-side applications: inthis phase, the earlier research focused on the evolution ofweb pages, and how to develop sites by reusing existingtechnologies and content, or to re-architecture the structureand links of the pages [14]. Further research confirmed theneed to study which processes were most effective whendeveloping new content: it was reported that websites weremostly expanded and eventually replaced, which created anissue with search engine spiders; and that web accessibility hasto play a major role in the development of websites [Holger etal 2011]. Finally, the testing of websites played a major rolein focusing the researchers attention on the static and evolvingfeatures of online content.In the third phase, the study of web systems was com-plemented considering the openness of such systems andhow collaboration is achieved in web system development.It is only recently that research on website evolution hasfocused on “users” as “content creators”: the developer anduser communities, the stakeholders and the whole web systemecosystem have an influence on the axes of products, processesand people.In this paper we describe three axis along which the recentresearch on web evolution has developed, focusing on the“products” (Section II), “processes” (Section III) and “people”(Section IV) axes, and discussing the open issues that each ofthem present to researchers.II. PRODUCTSIt is hard to imagine what would be the web today withoutsome technologies born without much fanfare but which havehad a very in-depth penetration. While Netscape and Microsoftand later on the Mozilla Foundation and Microsoft were fight-ing for browser predominance, technologies arose to changethe face of the web and shape it as we know it now.With an increasing number of websites to work on, de-velopers started recognising the importance of code reuse andabstraction. A small number of very popular libraries gainedprominence in those years - with use across large numberof web sites. This included software as Counter (born circa1995), FormMail (1995) and phplib (1998). The issues relatedto maintainability were also reflected in the rise of software asWML (Website Meta Language, created in 1996), the use ofServer Side Includes (included in Apache in 1995) and the useof content management systems (Slashdot was created in 1997and Slash shortly after). Web technologies as mod rewrite(circa 1989) and session-based URLs were also popularisedin the 1990s, and allowed to move away from the staticrelationship between files and URLs.On the web applications side, Geocities (1995) and Hotmail(1996) were born in 1995 and phpNuke and SquirrellMail in1999; companies of any size were started offering complexservices on top of Open Source stacks.Popularity and reachability were important issues and de-velopers were striving to find solutions. RSS (1995) allowedblogs and web sites in general to increase their popular-ity through syndication. LinkExchange and LinkTrade werefounded in 1996 and 1997, allowing websites to increase theirpopularity; at his peak link exchange reached more than halfof Internet-enabled households.Because of their public nature, web systems raised theimportance of accessibility in web systems. Early research em-phasized the readability of web pages [4] and need for “plain”language as well as the needs of minority language users [11].Usability and accessibility research predated research in humanfactors and ergonomics, from which it derived most of the earlyresearch methods (Nielsen, 1993).A. Open Issues: Security, Innovation, and SustainabilityAt the time of writing, Open Source software dominatesthe web. Netcraft statistics1 show that Apache is still themost popular web server (from the time in which they startedrunning their survey in 1995. As other players, as Nginix, startgrowing their market share, proprietary web servers seem moreand more relegated to niche roles. PHP outperforms all otherprogramming languages as number of websites2; Drupal andWordpress have a combined market share of 51%.This means that the bio-diversity that characterised theearly days of the web is disappearing. Most web sites arebuilding on top of the same set of technologies and usingsimilar software stacks – which has implications when it comesto security. Even more dangerously, anecdotal evidence seemsto indicate that most web sites do not update regularly theirsoftware stack – opening themselves to hackers.There are indications that innovation is well alive; nichetechnologies keep mushrooming and the last few years haveseen the popularisation of concepts as “cloud hosting”, “virtualservers”, “no-sql databases” and “Content Delivery Networks”.In the coming years, well be probably seeing more progressin this direction - with further separation between the largemajority of the web sites using the same software stack andinnovators testing and popularising new paradigms.III. PROCESSESEarly on it was clear to some that traditional softwaredevelopment processes and methods whilst relevant to thedevelopment of web systems needed re-thinking in the lightof early web system development. Metrics used to accessweb products and processes needed some adaptation to beapplicable to web systems; and new metrics such as “depthof linking” were devised [19]. Earlier research had alreadysuggested that study of metrics obtained from web sites overtime provided a means to predict when a web site might bere-structured and also analysis of web content could be fruitfulto identity replicated content similar to code clones [18], [5].Other studies by Boldyreff with Dalton and Kyaw, high-lighted the need for systematic development and maintenanceprocesses for web systems [9], [10], [13], [6]. Kyaws surveyfound that web hypermedia design methods being promotedwere derived largely from Object Oriented approaches andDatabase design approaches. Already at this time it was clearthat web systems presented many of the challenges of moretraditional large software systems and that existing methodsand tools could be employed in their development and main-tenance albeit with some adaptation. A fuller summary of thispioneering research on web system engineering can be foundin the abstract quoted below from [3]:Since the mid 90s, we have been studying Web developmentand maintenance at Durham. One aspect of the researchhas been concerned with characterizing the evolution of Websites over time. Another has been concerned with determiningappropriate process models of Web development and mainte-nance. Overlaying this research as been work on Web metrics:1http://news.netcraft.com/archives/2013/04/02/april-2013-web-server-survey.html2http://trends.builtwith.com/frameworkfirstly to evaluate web application quality, secondly to describechange, and thirdly to guide our research on process modelsfor web engineering. Working with small to medium enterprisesdeveloping commercial web-based applications has given ourresearch a firmly based practical emphasis and empiricalgrounding.All of our research has been leading towards the establish-ment of web site engineering as a new discipline within Soft-ware Engineering. An overriding concern has been determininghow to build the foundations of web site engineering basedon the lessons that can be learnt from traditional SoftwareEngineering, the identification of the new challenges intro-duced by taking an engineering approach to web site evolution,both development and maintenance aspects, and the uniqueproblems posed by the web and its associated technologiesand innovative applications.What we failed to recognise at the time was the impactthat open source software engineering and open on-line col-laborative communities developing web system content as wellas code would have on our current web systems and theirevolution.A. Open Research IssuesThe growth of distributed development and maintenance inrecent decades has posed challenges for many large softwaresystems and web systems are no exception. Global softwaredevelopment has brought not only a heterogeneity of systemcomponents but also of methods and processes used in asystems development and maintenance. The result has beenmulti-dimensional evolution and this is exhibited by many webbased systems in the extreme as they are often composed ofdifferent technologies, multiple components and web servicesdeveloped and maintained by diverse teams, each componentand service manifesting its own evolutionary path presentingthe overall system manager with a multitude of paths tounderstand and attempt to manage.Few web systems today have been developed by a sin-gle team following common processes. This heterogeneity ofprocesses and its impact on development and maintenance asmanifest through multi-dimensional evolution poses the singlegreatest challenge to understanding web systems which ofcourse is crucial for their continued and successful overallevolution. This links up with the people issue as more or lessany one can contribute to open source software and contenton the web.IV. PEOPLEOne of the most unforeseeable effects that the evolution ofweb systems underwent was opening the content creation toanyone, which culminated in the so called Web 2.0 revolution.This change of perspective put the users as the creators of thecode and content in many different venues. During the lastfew years, the content created and maintained online by users(and termed User-Generated Content, or UGC [20], [1]) hasbecome substantial in quantity, relevant in quality [8], and cen-tered around major topics and websites: multimedia (YouTube,Flickr, DeviantArt, etc), expert knowledge on specific topics(Street maps [12], Slashdot.org, IMDB, Wikipedia, etc), letalone all the source code released with open licenses throughwell known OSS repositories (SourceForge, Google Code,etc). The majority of such UGC’s faces an “uncontrolled,self-organized community of volunteer contributors, withoutthe traditional tight conditions and organizational policiesimposed in industrial production environments” [16].The majority of such UGCs faces an uncontrolled, self-organized community of volunteer contributors, without thetraditional tight conditions and organizational policies imposedin industrial production environments [5]. From the researchstandpoint, some of these UGCs (for instance, the Wikipediapages and the source code of OSS projects) are based onmeasurable effort of volunteers and produce measurable outputwith a determined productivity that an be tracked throughoutthe contents evolution, by parsing the recorded history ofchanges.A. Open IssuesThe two main issues that user-generated online contenthave to face are• the credibility of the published resources, and• the sustainability issue.On the one hand, the creators of online content do nothave an objective way to describe how credible or accurate isthe information that they are putting into the web. One suchexample are the sites that collect the reviews and commentsby customers on products or services, to be used by othercustomers to form a judgement on the quality of such productsor services.So, as visible in the Figure 1, even if a site like TripAdvisorshows a sustained intake of reviews by customers, and thejudgements of customers (rating between 1 and 5) depict anearly perfect experience, the number of reviews is still muchlower than the potentially much larger number of customerswho “physically” visited the premises of a restaurant. Thisraises an issue of credibility and bias of the reviews posted,since they could represent the views of a sample of customersmuch smaller (and biased) than the real user base.Fig. 1. Number of reviews and average grade per week of a well knownLondon restaurantAnother such example is the collaboratively editedWikipedia project, where pages are created and maintained byhundreds of online editors: most Wikipedia pages are accessedfor information, and their utility or credibility can be measuredby the number of views that they have received overall[7];while another way of determining its credibility is at the levelof individual and subjective effort[17].On the other hand, the online user-generated content facesthe issue of sustainability: user-generated content shows verycommon and recurring patterns where an initial phase ofsustained growth is followed by a various descending phases,which eventually decline into zero, as visible in the Figure 2.Fig. 2. Number of reviews and average grade per week of a well knownLondon restaurantV. CONCLUSIONSThe evolution of web systems over the last twenty yearsfrom humble hypertext systems to sophisticated large dis-tributed systems has been an amazing achievement form boththe technological as well as the societal standpoints. Here websystems evolution has been considered along the dimensionsof products, processes and people.The public nature of the web and its openness havebeen significant factors in its evolution. Tim Berners Lee in“Weaving the Web” envisaged the web as both readable andwritable, and this has definitely come to pass in the last decade.Sustaining the future evolution of web systems will be asmuch a technological and engineering problem as a socialproblem, as we gain a better understanding of how open on-linecollaborative communities develop and function effectively andtheir role in driving future web evolution.REFERENCES[1] G. M. Alluvatti, A. Capiluppi, G. De Ruvo, andM. Molfetta. User generated (web) content: trash or trea-sure. In Proceedings of the 12th International Workshopon Principles of Software Evolution and the 7th annualERCIM Workshop on Software Evolution, IWPSE-EVOL’11, pages 81–90, New York, NY, USA, 2011. ACM.[2] M. F. Arlitt and C. L. Williamson. Web server workloadcharacterization: The search for invariants. In ACM SIG-METRICS Performance Evaluation Review, volume 24,pages 126–137. ACM, 1996.[3] C. Boldyreff, E. Burd, and J. Lavery. Towards theengineering of commercial web-based applications. InInternational Conference on Advances in Infrastructurefor Electronic Business, Science, and Education on theInternet. Citeseer, 2001.[4] C. Boldyreff, L. Burd, J. Donkin, and S. Marshall. Thecase for plain english to increase web accessibility. InWeb Site Evolution, 2001. Proceedings. 3rd InternationalWorkshop on, pages 42–48. IEEE, 2001.[5] C. Boldyreff and R. Kewish. Reverse engineering toachieve maintainable www sites. In Reverse Engineering,2001. Proceedings. Eighth Working Conference on, pages249–257. IEEE, 2001.[6] C. Boldyreff and P. Kyaw. A survey of hypermedia designmethods in the context of world wide web design.[7] A. Capiluppi. Similarities, challenges and opportunitiesof wikipedia content and open source projects. Journalof Software: Evolution and Process, 2012.[8] M. Cha, H. Kwak, P. Rodriguez, Y.-Y. Ahn, and S. Moon.I tube, you tube, everybody tubes: analyzing the world’slargest user generated content video system. In Proceed-ings of the 7th ACM SIGCOMM conference on Internetmeasurement, IMC ’07, pages 1–14, New York, NY,USA, 2007. ACM.[9] S. Dalton. A workbench to support development andmaintenance of world-wide web documents, departmentof computer science, university of durham, 1996.[10] S. Dalton and C. Boldyreff. Web maintenance – thenew frontier. In Proceedings of Durham MaintenanceWorkshop, Sept.1996., 1996.[11] J. Donkin, C. Boldyreff, L. Burd, and S. Marshall. Sup-porting sign language users of web-based applications: afeasibility study. In HCI, pages 291–295, 2001.[12] M. M. Haklay and P. Weber. Openstreetmap: User-generated street maps. IEEE Pervasive Computing,7(4):12–18, Oct. 2008.[13] P. Kyaw. An investigation of web-based hypermediadesign support: methods and tools. PhD thesis, DurhamUniversity, 1998.[14] J. Martin and L. Martin. Web site maintenance withsoftware-engineering tools. In Web Site Evolution, 2001.Proceedings. 3rd International Workshop on, pages 126–131. IEEE, 2001.[15] D. Mosberger and T. Jin. httperf – a tool for measuringweb server performance. ACM SIGMETRICS Perfor-mance Evaluation Review, 26(3):31–37, 1998.[16] F. Ortega. Wikipedia: A quantitative analysis. PhD thesis,Universidad Rey Juan Carlos – Escuela Te´cnica SuperiorDe Ingenierı´a De Telecomunicacio´n, 2009.[17] P. Pirolli, E. Wollny, and B. Suh. So you know you’regetting the best possible information: a tool that increaseswikipedia credibility. In Proceedings of the SIGCHIConference on Human Factors in Computing Systems,pages 1505–1508. ACM, 2009.[18] P. Warren, C. Boldyreff, and M. Munro. The evolutionof websites. In Program Comprehension, 1999. Proceed-ings. Seventh International Workshop on, pages 178–185.IEEE, 1999.[19] P. Warren, C. Gaskell, and C. Boldyreff. Preparing theground for website metrics research. In Web Site Evolu-tion, 2001. Proceedings. 3rd International Workshop on,pages 75–85. IEEE, 2001.[20] S. Wunsch-Vincent and G. Vickery. Participative web:User-created content. Working Party on the InformationEconomy, page 74, 2007.

A survey of hypermedia design methods in the context of world wide web design.

A workbench to support development and maintenance of world-wide web documents, department of computer science, university of durham,

An investigation of web-based hypermedia design support: methods and tools.

httperf – a tool for measuring web server performance.

I tube, you tube, everybody tubes: analyzing the world’s largest user generated content video system.

Openstreetmap: Usergenerated street maps.

Participative web: User-created content. Working Party on the Information Economy,

Preparing the ground for website metrics research.

Reverse engineering to achieve maintainable www sites.

Similarities, challenges and opportunities of wikipedia content and open source projects.

So you know you’re getting the best possible information: a tool that increases wikipedia credibility.

On the sustainability of web systems evolution

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