1 Hypermedia Design Models & Methodologies Dr Gary Wills IAM Research Group © University of Southampton

2 Aims of Lecture To present the major design models and methodologies. –HDM –RMM –OOHDM To briefly look at: –Design environments –Design patterns

3 Why Do We Use Design Models Give a discipline approach and structure to the design process –Makes visible the activities to be undertaken –Identify the deliverables –Aids organisation to plan Staff, schedules, budgets, project management –Aids communication between Analysts, designers, implementers and clients

4 Hypermedia Design Model (HDM). Originally developed by Garzotto et al around 1993 This is a design model and not so much a methodology Allows the documentation and comparison of designs

5 HDM- Authoring Authoring in the Large –Overview of information elements – Navigational structures –Independent of node content Authoring in the Small –Development of the node contact –Captures semantics of the the application

6 HDM-Entities Entities –a physical object or concept in the domain –Grouped into entity types. –Autonomous pieces of information –Consist of a hierarchy of components Components –Represent an abstraction of a set of units Units –Represent information from different perspective

7 HDM. – Entity Relationships Different from tradition E-R diagrams –Complex inner structures –Default browsing semantics (structure) Perspective –Syntactical device to organise information –All components of an entity have the same number of perspectives as the entity.

8 HDM.-links Links in HDM –Capture the domain relations –Capture the navigational patterns Link Types –Structural links: connect together components belonging to the same entity. –Perspective links: connect together the different units that correspond to the same component. –Application links: denote arbitrary, domain dependent relationships

9 HDM. -Schema A schema (a diagrammatic outline) describes the application at a global level –Independent of file structure and implementation A schema definition specifies a set of entity types and link types. A schema instance is a collection of entities, components, units, and links that satisfy the definitions of the schema

10 HDM.- Summary HDM is a design model –HDM consists of typed entities which in turn are composed of components. –Entities and components are connected by structural links or application links. – An HDM schema is a set of entity and link type definitions –A schema instance is a set of actual entities and links. –HDM is a top-down design process for the development of applications

11 The Relationship Management Methodology (RMM). Originally developed by Isakowitz et al in 1995 This is a design methodology based on similar concepts as HDM Applicable to a narrow set of data –Volatile data that requires regular updating

12 RMM. RMM provides both a design model and a set of steps to aid implementation. Uses a form of E_R diagram –Relationship management data MODEL The RMM is a full design life-cycle model The methodology core focuses on the design phases

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14 RMM.-Step 1 E-R Diagram Information space analysed and modelled using E-R diagram –Well known and documented technique –Identifies entities and relationships –Focus on inherent structure not domain information use –Similar techniques to reduce many-to-many relationships Slight difference from E-R –Links are directional

15 RMM.- Step 2 Slice Design Determine how the information in the entity is –Presented to the user, – How the user may access it. Attributes of a entity instance are grouped into slices –Structural links: links between slices of same entity –Associated links: links between slices from different entities

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17 RMM. – M Slice A limitation to slicing –Can only slice up an entity New type of slice, m-slice –Models presentation units that contain information from more than one entity. –Models only information not presentation –Can be nested

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19 RMM. -Step 3 Navigational Design Designing the navigation paths through the entities. Described in generic terms and not hard coded. –Aids updating of the information –Achieved by referring to properties of the entities and their relationships. Conducted in parallel with S2

20 RMM- Remaining Steps S4 conversion protocol: –This step transforms each element on the RMDM diagram into an implementation object.. S5 user-interface design: –Design of interface components using the RMDM.. S6 run-time behaviour: –This stage considers the functionality of the application. S7 construction and testing:

21 RMM. - Summary Based on entity-relationship modelling. Focuses the design stage. Most appropriately used for applications. When –High degree of structure –High volatility of information Does not tied the designers to any specific implementation RMM takes a top-down approach to the design but does not support iteration

22 The Object Oriented Hypermedia Design Model, (OOHDM) This methodology was proposed by Schwabe et al. They say that a good Web application should be, first of all, a good hypermedia application. OOHDM builds a hypermedia application using an object-oriented framework. The design method uses a four-step process, each focusing on a particular design control.

23 OOHDM- Conceptual Analysis The main aim of this step is to capture the domain semantics as naturally as possible. Little concern is made of the type of user, task undertaken, functionality or structure. Results in a conceptual schema built out of subsystem classes and relationships.

24 OOHDM-Navigational Design Reorganised the information to take into account the users tasks/profiles – Define a navigational model in terms of nodes, links and access structures. –Avoids the redundant information and prevent the user getting lost in hyperspace. Independently of the conceptual model.

25 OOHDM-Abstract Interface Perceptible interface objects are defined in terms of interface classes. Interface behaviour is declared specifying –how to handle external and user generated events – how communication takes place between navigational and interface objects. A clear separation –allows different interfaces for the same navigational model, giving a higher degree of independence.

26 OOHDM-Implementation: The designer maps the navigational and interface models into a concrete object. The conceptual domain-use relational database and scripts

27 OOHDM- Separation of the design into clear steps allows the designer to focus on the important issues in each step. OOHDM does not cover the early aspects of the design process nor does it address how the steps are coordinated

28 OOHDM-Summary An OO incremental based design method with hypermedia domain specific extensions There are four main activities – Conceptual, design Navigation design, Abstract interface design, Implementation By separating the different design phases OOHDM improves maintainability OHDM is an iterative approach, yet it does not describe explicitly how the design phase are coordinated

29 Applying and Adapting the Methodology. You will need to adapt the model and methodology to you requirements –Principles the same, examples different –Modify the product model by adding domain specific entities and removing redundant entities –Modify the activities to reflect the changes in the product model, even add or remove activities. –Modify the outputs to reflect the changes to the activities and add or remove outputs

30 Tools and Environments The design methodology is independent of implementation solution. A design environment are required –A fast experimental feedback loop. –Tools for generalisation and instantiating models. –Easy and unconstrained cloning tools. –The ability to easily build solutions that may be evaluated directly. –Integrating light prototyping

31 Tools and Environments Tools- –Golden rule: First decide the methodology to be used, implement it, then look for opportunities to enhance it by using a tool. –Support for a specific methodology, i.e, RMCase –General tools i.e ColdFusion

32 Design Patterns Capturing design rules that emerge from the design –Identify common problems during design –Identify alternative solutions –Uses a shared vocabulary-model independent –Helps newer team member learn quickly Does require time, as information entered into a knowledge base

33 Design Patterns;- Structure The pattern should be clear, consistent and in a uniform structure. –Always give the pattern's context –Problem and interaction of events –Elements of the solution –Try to include examples –Use a naming convention

34 Design Patterns :- Examples Organising information space: –What are the effective ways to organise the information to aid navigation and yet also suit human cognition Organising the interface: –What type of interface is appropriate in what circumstance. Implementation: –Implementing the appropriate navigation aids. Process: –Often captured in a methodology as described above.

35 Summary HDM –A model –Use E-R diagrams –Used as the basis of the other methodologies RMM –E-R based –Slice entities OOHDM –OO techniques used

36 Summary No perfect design model as yet –You need to modify and methodology used. Tools –Choose your methodology first Design patterns –Captures your ‘neat’ ways of solving a problem