Tuesday, February 17, 2009
Web Modeling - Web Development by Model Driven Approach
Modeling in the IT arena is focusing on to visualise the concept defined in wordings, i.e., a model represents a part of reality (target) which was specified by a modeling view and described by modeling facilities in order to the purposes for recognition, understanding, and manipulation of the target.
Web Modeling:
It is a branch of "Web Engineering", which majorly addresses the issues related to the web application's design and development. It is as similar as we have application modeling tools for object oriented programming i.e., UML.
The main orthogonal models that are involved in complex Web application design are: data structure, content composition, navigation paths, and presentation model.
There are several web modeling languages and notations are available, some of them are as follows:
1. OOHDM ((Object Oriented Hypermedia Design Method)
It was one of the first methods to postulate the separation of concerns that defines its various models - requirements, conceptual, navigation, abstract interface and implementation.
2. WebML (Web Modeling Language)
It provides graphical, yet formal, specifications, embodied in a complete design process, which can be assisted by visual design tools, like WebRatio.
3. UWE (UML-based Web Engineering)
It follows the separation of concerns building separate models for requirements, content, navigation, presentation, process, adaptation and architecture.
Here we will describe more about the WebML (Web Modeling Language)
Requirements for Web modeling
1. Expressiveness
1.1 Real-life cases should be expressible
1.2 Frequently used design patterns should be captured
2. Ease of use
2.1 Intuitive notation
2.2 Clear semantics
2.3 Consistency checks
3. Implementability
3.1 Efficient mapping to physical data structures
3.2 Flexible code generation from behavioral specifications
Purpose of WebML
1. WebML aims at providing a structured approach to the design of Data-intensive Web sites.
2. A set of integrated Models should help designers in high-quality Web sites production.
3. All the facets of Web design should be addressed.
4. Use of old or uncoherent methodologies becomes deprecated.
The WebML models
WebML: a conceptual language for high-level design of data-intensive web sites
Following Models Could be produced by WebML
Structure: data organization.
Derivation: redundant data definition.
Composition: definition of site pages as set of subpages and elementary publishing units.
Navigation: definition of links between pages and between units.
Presentation: positioning of the units in the page and definition of graphical appearance.
IMPORTANT:
WebML is not a good tool for small and static websites.
1. Structure Model
Simplified Entity-Relationship model
1. Binary relationships between entities
2. IS-A hierarchies
3. Simple typed attributes in entities
5. Derivation model can be applied for redundant data
Above diagram is showing Structural Model
2. Derivation Model
Redundant data can be easily specified using a WebML-OQL (Object Query Language).
E.g.:
Author.BooksNumber = count(self.Author2Book)
BestSeller := Book where Book.Sales > 50,000
Above diagram is showing Derivation Model
3. Hypertext Model
1: Content Units (Composition)
2: Links (Navigation)
3: Pages (Composition)
4. Composition
To publish information about A SINGLE object (e.g. AuthorDetail)
5. Navigation Model: Links
Semantics of a link:
1. Moving from one place to another
2. Transporting information from one place to another (navigation context)
3. Activating a computation (side effect)
6. Composition: Pages
A Page is a structured container of units and links
1. Possibly structured in and/or sub-pages
2. Abstraction of screen, frame, card, deck...
3. Permits one to cluster related information for more efficient communication
Contd.....
Future Technologies for Mobile Devices
Bluetooth 3.0 specification will be released in 2009 (at which point its feature set will be frozen), with devices starting to arrive around 2010. Bluetooth 3.0 will likely include features such as ultra low-power mode that will enable new devices, such as peripherals and sensors, and new applications, such as health monitoring.
UIs have a major effect on device usability and supportability. They will also be an area of intense competition in 2009 and 2010, with manufacturers using UIs to differentiate their handsets and platforms. New and more-diverse UIs will complicate the development and support of business-to-employee (B2E) and business-to-consumer (B2C) applications.
Organizations should expect more user demands for support of specific device models driven by interface preferences. Companies should also expect consumer interfaces to drive new expectations of application behavior and performance. Better interfaces will make the mobile Web more accessible on small devices, and will be a better channel to customers and employees.
Location awareness makes mobile applications more powerful and useful; in the future, location will be a key component of contextual applications. Location sensing will also enhance systems, such as mobile presence and mobile social networking.
The growing maturity of on-campus location sensing using Wi-Fi opens up a range of new applications exploiting the location of equipment or people. Organizations delivering business or consumer applications should explore the potential of location sensing; however, exploiting it may create new privacy and security challenges.
802.11n
802.11n boosts Wi-Fi data rates to between 100 Mbps and 300 Mbps, and the multiple-input, multiple-output technology used by 802.11n offers the potential for better coverage in some situations. 802.11n is likely to be a long-lived standard that will define Wi-Fi performance for several years.
High-speed Wi-Fi is desirable to stream media around the home and office. From an organizational perspective, 802.11n is disruptive; it's complex to configure, and is a "rip and replace" technology that requires new access points, new client wireless interfaces, new backbone networks and a new power over Ethernet standard.
However, 802.11n is the first Wi-Fi technology to offer performance on a par with the 100 Mbps Ethernet commonly used for wired connections to office PCs. It is, therefore, an enabler for the all-wireless office, and should be considered by companies equipping new offices or replacing older 802.11a/b/g systems in 2009 and 2010.
Display technologies
Displays constrain many characteristics of both mobile devices and applications. During 2009 and 2010, several new display technologies will impact the marketplace, including active pixel displays, passive displays and pico projectors.
Pico projectors enable new mobile use cases (for example, instant presentations projected on a desktop to display information in a brief, face-to-face sales meeting). Battery life improvements are welcome for any user. Good off-axis viewing enables images and information to be shared more easily. Passive displays in devices, such as e-book readers, offer new ways to distribute and consume documents. Display technology will also become an important differentiator and a user selection criterion.
The mobile Web is emerging as a low-cost way to deliver simple mobile applications to a range of devices. It has some limitations that will not be addressed by 2010 (for example, there will be no universal standards for browser access to handset services, such as the camera or GPS).
However, the mobile Web offers a compelling total cost of ownership (TCO) advantage over thick-client applications. Widgets (small mobile Web applets) are supported by many mobile browsers, and provide a way to stream simple feeds to handsets and small screens. Mobile Web applications will be a part of most B2C mobile strategies. Thin-client applications are also emerging as a practical solution to on-campus enterprise applications using Wi-Fi or cellular connections.
Wireless broadband exploded in 2008, driven by the availability of technologies such as high-speed downlink packet access and high-speed uplink packet access, combined with attractive pricing from cellular operators.
The performance of high-speed packet access (HSPA) provides a megabit or two of bandwidth in uplink and downlink directions, and often more. In many regions, HSPA provides adequate connectivity to replace Wi-Fi "hot spots," and the availability of mature chipsets enables organizations to purchase laptops with built-in cellular modules that provide superior performance to add-on cards or dongles.
Near Field Communication (NFC)
NFC provides a simple and secure way for handsets to communicate over distances of a centimeter or two. NFC is emerging as a leading standard for applications such as mobile payment, with successful trials conducted in several countries. It also has wider applications, such as "touch to exchange information" (for example, to transfer an image from a handset to a digital photo frame, or for a handset to pick up a virtual discount voucher).
Gartner does not expect much of the NFC payment or other activities to become common, even by 2010, in mature markets, such as Western Europe and the US. NFC is likely to become important sooner in emerging markets, with some deployments starting by 2010.