Architecturing Enterprise
                                                                     Information Portals for
   ...
For the long term, we will return to cover the individual issues in
                                                      ...
associate a value in D with each variable v in V. A state is the         Property 1 guarantees that two structures, mainly...
by a smaller equivalent one. This facilitates its study and                Taking Larson & Czerwinski’s empirical value of...
Estimated menu levels as a function of site size

                                                        12




         ...
crucial to distinguish between these two navigation methods           communicate the best practices of user interface des...
•     Sub-sites: Shallow main menu or broad portal leading to
      smaller sub-sites with simple navigation architectures...
•   To optimize menu-based navigation:           Increase menu
    breadth as close as possible to 16, Balance the tree as...
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Architecturing Entreprise Informations Portals For Navigation

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Architecturing Entreprise Informations Portals For Navigation

  1. 1. Architecturing Enterprise Information Portals for Navigation Organiser un portail d’information d’entreprise pour la navigation Abstract An enterprise portal – also known as an enterprise information portal (EIP) or corporate portal – links information, people and Ahmed Seffah(1,2) business processes while providing a unified web-based user EHL Lausanne, Switzerland interface. One of the major engineering and management Department of Computer Science, challenge of enterprise portals is the navigation system which University Concordia, Montreal Canada keeps the information always accessible. Based on empirical seffah@cse.concordia.ca study and formal modeling of menu-based navigation systems, we discover unexpected problems with navigation in large ahmed.seffah@ehl.edu portals, and we deduce solutions and patterns for improved navigation. In the context of these results, we discuss existing and new design patterns, and how to apply these patterns to Daniel Engelberg(1) different sizes of architecture. Department of Computer Science, University Concordia, Montreal Canada Keywords Enterprise Information Portals, Information Architecture, Web site design, navigation system and patterns Résumé Un portail d’information d’entreprise (EIP) vise à lier l’information, les employés et les processus d’affaire et métiers à travers une interface homme-machine basée Web d’accès à l’information et aux services sous-jacents. Un des défis majeurs dans l’ingénierie et la gestion d’un EIP et de son succès auprès des futurs utilisateurs est le système de navigation. Comment l’usager navigue et retrouve t-il l’information sur le portail. En analysant formellement et empiriquement un système de navigation exploitant des menu dans le cas d’une architecture hiérarchique d’un portail de différentes tailles, nous avons identifier plusieurs patrons de navigation. Nous discuterons dans ce papier des aspects formels et empiriques qui nous permis d’aboutir à ces patrons tout en montrant comment ces patterns facilitent la navigation en fonction de la seule connaissance sur la taille du site. Mots clés : Portail d’information d’entreprise, Architecture d’information, Patrons et système de navigation, design de site Web
  2. 2. For the long term, we will return to cover the individual issues in more detail and with more empirical and formal proof. 1. Introduction An Enterprise Information Portal (EIP) is a Web-based 2. Modeling Web Navigation: A application that enables organizations to unlock internally and externally stored information and provide users a single gateway Theoretical Framework to personalized information needed to make informed business decisions. What differentiates portals from static Web sites is While attempting to model Web site architecture, our objective their ability to incorporate data from multiple sources in multiple is double. formats, yet organize and present it to the end users. Just as users can jump from news reports to shopping malls on Yahoo, First, we aim to identify different attributes such as Web site Enterprise Information Portals enable them to jump from size and their properties that are not easy to discover from the business intelligence systems to ERP and CRM applications to EIP source code. Such properties can be used to automatically sales reports, all without leaving their browsers. validate EIP. Examples of verifications include page reachability and navigation path correctness. However, organizing Web functionality and information into a structure that users are able to navigate intuitively doesn’t However, we also advance that a formal model of EIP can drive happen by chance (Nielsen, 2005). Navigating through the Web the process of identifying and applying appropriate navigation is to visit site pages in a structured order (moving from page to patterns in particular for Web sites during the maintenance and page according to the site internal links) or in a random order reengineering step or during early design and prototyping (). For (taking an unsystematic strategy such as using the Back button example, if you find that a Web page has the properties of a on a browser, entering a new URL address, etc.). All of these home page, then all the navigation design patterns for home Web navigation mechanisms can be ineffective (Brinck, 2001; page can be considered for the design of this page. Melody, 2005). In this second direction, the formal model will complement or As a consequence and as shown in several studies, not only is supplement the empirical and user-oriented studies that model this extremely frustrating for users, but it has serious Web site architectures based on the user experiences. Combined repercussions for organizations. Information architecture is the together, the formal and empirical models are the foundations of term used to describe the way information is grouped, the a systematic approach for automating the development of navigation methods and terminology used within the system. navigation system for EIP and for their management. Effective information architecture should enable people to step logically through a system confident they are getting closer to The significance of a formal model of EIP architecture comes the information they require. from the fact that the content of EIP can be modeled as a finite state machine (FSM). This is not the only way, but among the Lou Rosenfeld and Peter Morville, in their seminal book, possible solutions. Information Architecture for the World Wide Web: Designing Large-Scale Web Sites, define the roles of navigation as: FMS can be represented as transition structures 1. The combination of organization, labeling, and schemes to where each state has a bounded description, and facilitate task completion and intuitive access to content. hence can be characterized by a fixed number of 2. The art and science of structuring and classifying boolean atomic propositions. information to help people find and manage information. The motivation of this research is to study navigation systems 1. It is always possible to extract a finite state according to different sizes and models of information model from EIP structure architecture and different contexts of use. We wish to ground this approach as solidly as possible in empirical evidences and 2. Some specific properties to be verifieda theoretical principles. Although a large number of architecture 3. Some problem of inconsistency can be avoided and usage parameters are involved in defining an information such as various stakeholders may have different architecture, the size of the architecture seems to be particularly properties in mind important. Therefore, we investigated the architecture size as a 4. Model checking techniques can be used for first and relatively unexplored determinant of navigation design validating a prototype (simulation) and selecting patterns. As discussed in the literature several other factors have and applying patterns to be considered including cognitive attributes, visual design a. layout, colors, fonts, etc. The first feature of a large EIP that has to be modeled is its To motivate our investigations, we begin by formalizing the states. In a static EIP, each Web page is a state. However, in a relationship between architecture size and menu depth. We then dynamic EIP where pages are dynamically generated by a analyze menu-based navigation systems, because they are the server-side program under user request, a state represents the most common navigation techniques. In order to quickly build page status at time ti. the foundation for design patterns-based framework, this paper relies on a combination of proven facts, best-guess assumptions, Let V = {v1, ……, vn} be the set of system variables which mathematics and logic. range over a finite set D. A valuation for V is a function that
  3. 3. associate a value in D with each variable v in V. A state is the Property 1 guarantees that two structures, mainly two valuation for V at a particular instant of time. information architectures, have the same behaviors. Property 1 In addition to state, we also need to know how the states change Two transition structures K and K’ are bisumation with respect to some user actions, which is given by a transition equivalent, denoted K ≡ K’ if: between the state before the action and the state after the action. So, the behaviors of the system can be described by the states and the changes of the states, namely transitions.  ∃ B such that for every s0 ∈ I in K there is an initial state s’0 ∈ I’ in K such that B (s0, s’0) Formally, the state transition graph by the name of Kripke structure is used to capture the behaviors.  In addition, ∀ s’0 ∈ I’ in K, ∃ s0 ∈ I in K / (B (s 0, s’0) Definition 1. Let AP be a set of atomic propositions. A kripke structure K over AP is a four duple K = (S, The second type of relation, called simulation, relates a structure I, δ, λ) where: to an abstraction (prototype, specification) of another structure.  S is the finite set of states Because the abstraction can hide some of the details of the original structure, it might have a smaller set of atomic  I ⊆ S is the set of initial states propositions. The simulation guarantees that every behavior of a structure is also the behavior of its abstraction. However, the  δ ⊆ S x S is a transition relation that must be abstraction might have behaviors that are not possible in the total, that is, for every state s ∈ S there is a state original structure. s’ ∈ S such that δ (s, s’). Namely, s’ is the next state of s. Definition 4 Given two structures K = (S, I, δ, λ) and K’ = (S’, I’,  λ: S -> 2AP is a function that labels each state δ’, λ’) with AP’ ⊆ AP. A relation H ⊆ SxS’ is a with the set of atomic propositions true in that simulation relation between K and K’ if and only if state for all s and s’, if B(s, s’) then the following conditions hold A computation of the above transition system is an infinite  λ(s) ∩ AP’ = λ’(s) sequence of states, where each state is obtained from the previous state by some transitions. This intuition is captured by a  for every state s1 such that δ(s, s1), there is a path as defined below. state s’1 with the property that δ’(s’, s’1) and H (s1, s’1) Definition 2. A path in the structure K form a state s0 is an infinite sequence of states ∏ = s 0 s1 s2 … such Simulation is generally used to replace a large architecture by a that for all i ≥ 0 δ (si, si+1). smaller architecture that satisfies temporal logic properties We will use the notation ∏n for the suffix ∏ that (specifications). begins at sn and ∏n for the ith state in the path. Property 2 In spite of the impressive proliferation of extra large portals, Structures K’ is a simulation of structure K, denoted state explosion is major problem. Before presenting the K ш K’ if: techniques that can be used to reduce the complexity of a Web site, we need first to introduce a notion of equivalence between  ∃ H such that for every initial state s0 ∈ I in K two structures. In what follow, we introduce two relations there is an initial state s’0 ∈ I’ in K for which H between structures: bisumalation and simulation. (s0, s’0) Definition 3 As part of the theoretical framework, we attempt to determine Given two structures K = (S, I, δ, λ) and K’ = (S’, I’, the relationship between the size of a site and the number of δ’, λ’) with the same set of atomic properties AP. A menu levels (depth) required to support it. Because depth is relation B ⊆ SxS’ is a bisumaltion relation between constrained by breadth, we start by reviewing the scientific K and K’ if and only if for all s and s’, if B(s, s’) then literature on ideal menu breadth. We will use the following the following conditions hold basic metrics:  λ(s) = λ’(s)  for every state s1 such that δ(s, s1), there is a   Breadth (B) = Number of elements per menu item Depth (D) = The number of embedded menu levels in a site state s’1 with the property that δ’(s’, s’1) and B or a part of a site (s1, s’1)  Size (S) = Total number of pages in a site  for every state s’1 such that δ(s’, s’1), there is a state s1 with the property that δ(s, s1) and B (s1, In the empirical studies, we have been considering Web s’1) sites that satisfy the properties defined in this section. We focussed only on static Web sites as defined here. In particular, we used property 2 to replace large architecture
  4. 4. by a smaller equivalent one. This facilitates its study and Taking Larson & Czerwinski’s empirical value of 16 items for patterns discovery. menu breadth, in a perfectly balanced tree-shaped architecture, simple calculation allows us to define the total number of pages supported as described in Theorem 1, below. However in reality, 3. Empirical studies on ideal menu tree-based architectures are usually unbalanced, i.e. different breadth (B) branches have different breadths and depths. Therefore to be more realistic about the total menu depth for a given size of site, we adjusted the calculation using the following rules and A considerable number of studies addressed the design of theorem: menus-based navigation systems (Norman, 1991) as well as their usage to Website navigation (Melody, 2002). The results are • Rule 1 (empirical): For the purposes of usability, the ideal somewhat complex to interpret, but they tend to highlight that menu breadth D is about 16 elements per menu. ideal menu breadth centres around 7 +/- 2 items, consistent with • Theorem 1 (mathematical/logical): In a perfectly balanced the limitations of short-term memory. architecture, the acceptable number of pages S supported by any depth D is S(D) = 16D + 16D-1 + 16D-2 … + 161+ 160 • Rule 2 (best guess from experience): Due to a number of factors, architectures will tend to be unbalanced in breadth However in a study using a larger and more realistic data set, and depth, and those unbalances will tend toward menus Larson & Czerwinski (1998) concluded that in fact, ideal menu that are less broad, i.e. less than the ideal of 16 items. breadth is probably closer to 16 items. This seems to be the most recent significant study on menu design. This study needs • Rule 3 (statistical): Unbalances accumulate, leading to to be extended and replicated to confirm their conclusions. more total levels than the ideal. • Rule4 (statistical): There is a small opposite effect of tendency toward the mean. 3.1 Theoretical ideal for relationship between site size (S) and number of menu levels (D) This leads to the following formula for estimating likely total menu depth. Table 1 summarizes the calculations, plotted in Figure 1. Likely total menu levels D = Ideal minimum (balanced) + Extra due to unbalance - Tendency toward the mean Pages Size range Label Ideal min. Likely Tendency Likely (approximate) levels extra to mean total (unbalance) 17 1 -100 Small 1 2 1 2 273 100 -1,000 Medium 2 3 1 4 4,396 1,000 -10,000 Large 3 4 1 6 69,905 10,000 - 100,000 Very large 4 5 1 8 1,118,48 100,000 - Extra large 5 6 1 10 1 4,000,000 Table 1: Number of menu levels required as a function of architecture size
  5. 5. Estimated menu levels as a function of site size 12 Number of levels 10 8 6 Likely 4 2 Minimum 0 1 3 17 5 96 48 27 90 43 18 69 11 Num ber of pages Figure 1: Estimated menu levels predicted as a function of site size • If Larson & Czerwinski were wrong and ideal menu 3.2 Empirical evidences on the relationship breadth is in fact about 7, then the fundamental issues don’t change: between site size (S) and number of menu o Ideal menu depth would be deeper for any given levels (D) size of architecture, by a factor of about 25%. o Menu depth in current sites could be improved by Due to the lack of empirical studies on the relationship between a maximum of only 25%. the size of architecture and the ideal number of menu required, • So menu-based navigation in large sites is laborious, and we analyzed the menu-based architecture of the Yahoo portal will continue to be so even after refinement. (www.yahoo.com). It is accepted that Yahoo contains over a million pages probably several million. 4. The Navigation Flaw in Large According to our predictions (see Figure 1), it requires at least Menu-Based Architectures 10 menu levels. Because Yahoo’s nodes list the number of pages contained within them, we were able to follow the scent of the largest branches to their terminal level in order to determine Most large information architectures currently adopt menu- the approximate size. Most of the deeper branches had a depth based approaches for navigation. Unfortunately, in a of 8-10 levels, and the deepest branch we could find had a depth hierarchical menu structure, almost all the pages are at the of 11 levels. This confirmed our prediction of 10 menu levels as deepest levels. This is due to the “iceberg effect” or “pyramid being the likely depth for this extra-large site. In a future study, effect”. In a balanced architecture, the percentage of pages at we will continue this empirical analysis with other extra large the deepest level is equal to the number of pages at the deepest sites. level divided by the total number of pages in the site, where B=breadth and D=depth: Because small sites are known to contain 1-2 levels, the data points at the two extremes of the curve are therefore validated % at deepest level = BD /(BD + BD-1 + BD-2 … + B1+ B0) with preliminary empirical values. And since the curve is most likely approximately linear (on a logarithmic scale), we can Due to the structure of tree-shaped architectures, this percentage therefore conclude that the “Likely” curve in Figure 1 is a valid is always high. For example in a balanced architecture with a approximation of reality for both large and small sites. menu breadth of 10 items, approximately 90% of the pages are at the deepest level, regardless of the number of levels. The percentage is in fact worse for a breadth of 16 items, at close to 3.3 Preliminary conclusions from empirical 94%. This effect can be reduced somewhat through various and theoretical analysis manipulations of architecture shape, but the effect remains very large as long as the basic tree structure is maintained. By From the empirical and theoretical analysis, we draw the narrowing breadth we reduce the percentage in the last levels, following conclusions that we consider as, an important input but we increase the total number of levels. for the applicability of patterns for different architectures: Therefore in a large architecture, users have to wade through a • In practice, large architectures use lots of menu levels (6-10 lot of irrelevant structures and content before they get to their levels). target. This is true even for usability-optimized combinations of • The actual number of levels in most sites is approximately depth and breadth. And this is the fundamental navigation flaw double of the ideal number of level required. This means in using menu-based navigation in large architectures. that there is room for improvement by up to a maximum of about 50%, and realistically a fair amount less than that. In brief, menu-based approaches are good for navigating within the target, but poor for navigating to the target. It is therefore
  6. 6. crucial to distinguish between these two navigation methods communicate the best practices of user interface design when designing navigation systems. The resulting appropriate with a focus on the user’s experience and the context of model for large architectures is a hybrid navigation model that use (Borchers, 2001)). we define as follow: A number of pattern languages have been suggested in 1. Navigate to the target using highly efficient bottom-up (data-based) methods such as search engines, intelligent HCI. For example, Van Duyne’s “The Design of Sites” agents and alphabetical indices as a front end to the (Duyne 2003), Welie’s Interaction Design Patterns (Welie architecture, on the home page. 2009), and Tidwell’s UI Patterns and Techniques (Tidwell 2. After the user finds their target in the results from the 2005) provided a large collection of patterns. Many of search engine or intelligent agent, present the target using a these patterns are applicable to Web-based application menu-based navigation interface. design (Welie, 2009; Taleb, 2006)), including patterns for navigation in large information architectures as well as for Although the hybrid model could become a new standard for visualizing and presenting Web information. many sites, its cost-effectiveness depends on the comparison between menu and search engine (or intelligent agent) usability In this research, we have been considering this existing in a given context of architecture and usage. The following collection of patterns mainly for navigation. In order to classify factors can be used to determine its success and context of use: them, we first established a set of criteria for selecting patterns: • Context of use. For example when the user has no idea • Define parameters for usability-relevant aspects of the what to look for, menu-based navigation may be preferable. design patterns. • The ability of the search engine or intelligent agent to • Since a given solution will have parameter values on all of present the target in the first few results the parameters, elaborate the list of parameters and the list • Getting users to trust search engines and intelligent agents of patterns separately. Arrange both lists in the simplest • Improving the search engine interface so that users can and flattest possible structure, and add cross-references know how to easily enter effective queries. between them, for example to permit filtering on all of the patterns that have a high value for a given set of To conclude, the best possible case in navigation is where effort parameters. Afterward, different views of the parameters and time are infinitely small. Any improvement in navigation and patterns can be created dynamically for the purposes of must operate within the space between this ideal and where we understanding their relationships or for choosing a design are today. But the best possible improvement to menu usability pattern. can constitute only a small part of the total potential improvement, due to mathematical constraints. Our resulting proposal for a first-draft taxonomy is as follows: In the future, the larger part of improvements to navigation will • Context of use: Browsing versus specific searching have to be determined by alternative approaches to menus, • Information structure: Highly structured vs. non- mainly bottom-up approaches that get us there faster. These structured, hierarchical vs. non-hierarchical include intelligent agents and key-word search engines. • Navigation in model-based (top-down) Alphabetical indexes are also a highly valuable and under-used technique for direct access to deeply embedded pages. o Menus: Deep vs. shallow, broad vs. narrow, adaptive vs. non-adaptive, sequential vs. simultaneous 5. Navigation Design Patterns for o Menu zone: Wide vs. narrow • Navigation in Data-based (bottom-up) Large Information Architectures o User-initiated vs. system-directed • Navigation in hybrid (model-based and data-based) The building architect Christopher Alexander first introduced the concept of design patterns in the late 1970s. In his two books , he discusses the capture and use of design knowledge in the 5.1 Typical design patterns for navigating format of patterns, and presents collections of pattern examples large sites to help architects and engineers with the design of buildings, towns, and other urban entities. To illustrate, Alexander proposes an architectural pattern called Wings of Light To understand the extent, to which we can improve design [Alexander et al. 1977], where the problem is: “Modern patterns for navigation, it is important to examine first, the buildings are often shaped with no concern for natural light - current patterns that used. The following sub-set of patterns they depend almost entirely on artificial light. But, buildings describes the most frequently used design patterns in large sites, which displace natural light as the major source of illumination based on our informal survey. are not fit places to spend the day.” • Simple universal: Shallow left-hand main menu for top In user interface design including Web sites, patterns have levels, usually permanent. After running out of top menu also been introduced as a tool to capture and disseminate levels, use a series of sequential one-level contextual menus in content zone. proven design knowledge, and to facilitate the design of • Portal: Very broad first and second level, leading to more usable systems. Patterns aim to capture and various simple forms of navigation at deeper levels.
  7. 7. • Sub-sites: Shallow main menu or broad portal leading to smaller sub-sites with simple navigation architectures. • Search engine: As a supplement to all of the above. Data-based navigation patterns: The following is a more complete list of approaches and major • User-driven: components. The list is far from exhaustive, but helps to o Key-word search: Simple vs. iterative communicate the flavour and abstraction level of design patterns (embedded) for navigation that we are targeting. Due to space limitations, o Key-word search: Contextual within current we can only list the title and a brief description, rather than the section vs. global full description format as described in Borchers (2001). The o Alphabetical index contents and structure of the list will be elaborated in future publications. • System-driven: Linear dialogue o Wizards Model-based navigation patterns (menus): • Intelligent agents • Simple universal (see above for definition) • Information portal: Broad first and second level on The following are some of the forgotten and rarely-used patterns home page • Deeply embedded menus (e.g. file manager menu) • Sub-sites: Shallow main menu or broad portal leading • Container navigation: Different levels of menu to smaller sub-sites with simple navigation displayed simultaneously in separate zones, e.g. architectures. Outlook Express or Netscape Mail • Permanent horizontal menu at top • Contextual (temporary) horizontal menu at top (called up by a higher-level menu or a link) • Permanent vertical menu at left The following are some of the new and experimental patterns • Contextual (temporary) vertical menu at right in that are being used content zone (called up by a higher-level menu or a • Hybrid approach: Key-word search to access target, link) followed by menu-based navigation within target • Shallow menus (1 or 2 levels in same menu) • Refreshed shallow vertical menus (see slide presentation) • Shallow vertical menus at left calling up contextual • Contextually adapted menus: Picking up the web by (temporary) menus in content zone, which call up a the current node (see slide presentation) new contextual menu at left, ad infinitum (Not recommended). Table 2 summarised our preliminary investigations on best • Bread crumbs: Navigation trail from home page down (appropriateness) of design patterns for small, medium, large to current page and extra large architecture sizes. Size Best design pattern for navigation Small • Simple 1- and 2-level main menus (permanent) Medium • Simple 1- and 2-level menus (permanent) supplemented by: o Contextual (temporary) vertical text menus in the content zone o Contextual (temporary) horizontal menus in the content zone Large • Hybrid approach: Key-word search to target followed by menu-based navigation within target o Within the target, use a navigation pattern consistent with the size of the target (small or medium) • Refreshed vertical menus • Deeply embedded menus Very and extra • Hybrid approach: Key-word search to target followed by menu-based navigation within target large o Within the target, use a navigation pattern consistent with the size of the target (small, medium or large) Table 2: Design patterns as a function of architecture size (See Table 1 for definition of size.) demonstrating that menus are good for navigating within the 6. Conclusion target, but relatively poor for navigation to the target. In this paper we present the first results of an ongoing research To solve this problem while extending our framework we offer project which aims to build a comprehensive framework for the following recommendations. identifying and applying navigation design patterns. The proposed framework uses a FSM to define navigation patterns as • To bypass menu-based navigation: Start with data-based a function of information architecture properties and the context rather than model-based search, for example: Key-word of use. The frameworks is based on empirical evidences search (search engines), Intelligent agents, Alphabetical indices
  8. 8. • To optimize menu-based navigation: Increase menu breadth as close as possible to 16, Balance the tree as much as possible, Consider new and alternative menu-based navigation patterns In particular, to significantly improve navigation, we will need to invest considerably more effort in designing and applying bottom-up navigation approaches such as intelligent agents, key- word search engines and alphabetical indices. References Alexander, C. (1979). The Timeless Way of Building. New York, Oxford University Press. Alexander, C., Ishikawa, S., Silverstein, M., Jacobson, M., Fiksdahl-King, I., and Angel, S. (1977). A pattern language - Towns, buildings, construction. New York, Oxford University Press. Borchers, J.O. (2001). A Pattern Approach to Interaction Design. New York, John Wiley & Sons. Duyne, D. K. van, Landay, J. A, and Hong, J. I., (2003), Design of Sites: Patterns, Principles, and Processes for Crafting a Customer-Centered Web Experience. Addison- Wesley. Garrido A., Rossi, G., Schwabe, D. (1997), “Pattern Systems for Hypermedia,” PLoP '97. Larson, K. & Czerwinski, M. (1998), Web Page Design: Implications of Memory, Structure and Scent for Information Retrieval, Proceedings of CHI 98, p. 25-32. Norman, K. (1991), The Psychology of Menu Selection: Designing Cognitive Control at the Human/Computer Interface, Ablex Publishing. Douglas K. van Duyne, James A. Landay, and Jason I. Hong, The Design of Sites: Principles, Processes, and Patterns for Crafting a Customer-Centered Web Experience, 2nd Ed., Upper Saddle River, NJ: Prentice Hall, 2007. Fogg B. J., Jonathan Marshall , Othman Laraki , Alex Osipovich Taleb, M., Javahery, H. and A. Seffah (2006) Pattern-Oriented , Chris Varma , Nicholas Fang , Jyoti Paul , Akshay Design Composition and Mapping for Cross-Platform Web Rangnekar , John Shon , Preeti Swani , Marissa Treinen, Applications, in Proceedings of DSV-IS 2006, Dublin, What makes Web sites credible?: a report on a large Ireland. quantitative study, Proceedings of the SIGCHI conference Tidwell, J. (2005) Designing Interfaces, O’Reilly, 2005. on Human factors in computing systems, March 2001, Welie M.V. (2009) Interaction Design Pattern. Available from Seattle, Washington, United States http://www.welie.com Melody Y. Ivory , Marti A. Hearst, Improving Web Site Design, Melody Y. Ivory and Rodrick Megraw. Evolution of Website IEEE Internet Computing, v.6 n.2, p.56-63, March 2002. Design. ACM Transactions on Information Systems. Jakob Nielsen's Alertbox, October 3, 2005: Top Ten Web Volume 23, Issue 4 (October 2005). Design Mistakes of 2005 Tom Brinck, Darren Gergle, Scott D. Wood, Usability for the Web: designing Web sites that work, Morgan Kaufmann Publishers Inc., San Francisco, CA, 2001 Dennis Fetterly , Mark Manasse , Marc Najork, Janet L. Wiener, A large-scale study of the evolution of web pages, Journal of Software Practice & Experience, v.34 n.2, p.213-237, February 2004.

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