Object Oriented Hypermedia Design Method (OOHDM)

Object Oriented Hypermedia Design Method (OOHDM) is a method for designing web applications. The development of hypermedia applications consists of four different design activities :

- Conceptual Design for OOHDM
In conceptual design, a conceptual schema is built that represents objects, relationships and collaborations existing in the target domain. To create class diagrams, aggregations and class representations, diagrams and other information, Unified Modelling Language(UML) is used.

- Navigational Design for OOHDM
In OOHDM, the navigational design is build over the view of conceptual design. It uses a predefined set of navigation classes like nodes, links, anchors and structures. Navigation design is expressed in two schema's, the Navigational Class schema and the Navigational Context schema.
Objects that are derived from classes defined in conceptual design are called navigational objects. A series of navigational classes or nodes are defined to encapsulate these objects.
Navigational design must take into account the way in which the user explores the hypermedia space.

-Abstract Interface Design
Abstract Interface Design specifies the interface objects. To represent the relationship between interface and navigation objects, a formal model of interface objects called Abstract Data View is used. The abstract data view defines:
- a static layout.
- behavioral component.

- Implementation
Any application-specific model, like OOHDM design, must be eventually implemented using an implementation technology. This activity represents a design iteration that is specific to the environment in which web application will operate.

Conceptual Data Models for Database Design

Conceptual modeling is an important phase in designing a successful database application. The database design process consists of a number of steps listed below:

Step 1: Requirements Collection and Analysis
- Prospective users are interviewed to understand and document data requirements
This step results in a concise set of user requirements, which should be detailed and complete.
- The functional requirements should be specified, as well as the data requirements. Functional requirements consist of user operations that will be applied to the database, including retrievals and updates.
- Functional requirements can be documented using diagrams such as sequence diagrams, data flow diagrams, scenarios, etc.



Step 2: Conceptual Design / Data Modeling
- Once the requirements are collected and analyzed, the designers go about creating the conceptual schema.
- Conceptual schema: concise description of data requirements of the users, and includes a detailed description of the entity types, relationships and constraints.
- The concepts do not include implementation details; therefore the end users easily understand them, and they can be used as a communication tool.
- The conceptual schema is used to ensure all user requirements are met, and they do not conflict.

Step 3: Database Design
- Two sub-steps called Database Logical Design which define a database in a data model of a specific DBMS and Database Physical Design which define the internal database storage structure are defined.
- It also defines file organization or indexing techniques.

Step 4: Database Implementation
- Many DBMS systems use an implementation data model, so the conceptual schema is transformed from the high-level data model into the implementation data model.
- This step is called logical design or data model mapping, which results in the implementation data model of the DBMS.

Step 5: Physical Design
- Internal storage structures, indexes, access paths and file organizations are specified.
- Application programs are designed and implemented.