The objects identified in the object—oriented analysis phases are grouped into classes and refined so that they are suitable for actual implementation. Unlike the traditional systems analysis where user requirements are gathered and then specifications are put on the requirements and users are then asked to sign off on the specifications, the object methodologies use a more iterative process where the requirements and specifications are reviewed repeatedly and the users are heavily involved. The major phases of software development using object—oriented methodology are object-oriented analysis, object-oriented design, and object-oriented implementation. Here, concurrency is modelled in the system level.

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The ternary or three-pronged type is the natural evolution of existing structured methods and has three separate notations for data, dynamics, and process. The unary type asserts that because objects combine processes methods and data, only one notation is needed. The unary type is considered to be more object-like and easier to learn from scratch, but has the disadvantage of producing output from analysis that may be impossible to review with users.

Dynamic modeling is concerned with events and states, and generally uses state transition diagrams. Process modeling or functional modeling is concerned with processes that transform data values, and traditionally uses techniques such as data flow diagrams.

Booch is the chief scientist at Rational Software, which produces Rational Rose. While the Booch methodology covers requirements analysis and domain analysis, its major strength has been in design. However, with Rumbaugh and Jacobson entering the fold, the relative weaknesses in analysis are disappearing rapidly.

For systems with complex rules, state diagrams are fine for those with a small number of states, but are not usable for systems with a large number of states. Once a single-state transition diagram has more than eight to 10 states, it becomes difficult to manage. For more than 20 states, state transition diagrams become excessively unwieldy.

Their methodology focuses on analysis of business problems, and uses a friendlier notation than that of Booch, Shlaer and Mellor, or the others that focus more on design. Classification structures correspond to the inheritance relationship between classes.

Composition structures define the other types of relationships between classes. Coad and Yourdon do not deal as well as Rumbaugh, Jacobson, and several other methodologies do with these structures.

The chief requirement was a simple methodology with an effective notation. The result was Fusion, which Coleman and others developed by borrowing and adapting ideas from other methodologies. They incorporated some major ideas from Booch, Jacobson, Rumbaugh, and others, and explicitly rejected many other ideas from these methodologies. Articles that Fusion practitioners have written have been some of the most pragmatic and useful about OOAD, but, unless you conduct a significant research effort, you generally hear much more about other methodologies than about Fusion.

Coleman did not use some of the major components of Rumbaugh and Shlaer and Mellor in Fusion, because the components were not found to be useful in practice. According to Jacobson: "You will need the complete The major distinguishing feature in Jacobson is the use case.

A use-case definition consists of a diagram and a description of a single interaction between an actor and a system; the actor may be an end user or some other object in the system. For example, the use-case description of an order-entry application would contain a detailed description of how the actor the user interacts with the system during each step of the order entry, and would include descriptions of all the exception handling that might occur.

According to Jacobson, a use case is any description of a single way to use a system or application, or any class of top-level usage scenario, that captures how actors use their black-box applications. An actor is an interface to the system, that is, something with which the system communicates, and may be a person or another program.

Jacobson adds that a use case is any behaviorally related sequence of transactions that a single actor performs in a dialog with a system, in order to provide some measurable value to the actor. Generally, you employ use cases to document user requirements in terms of user dialogs with a system. Use cases appear first in the requirements model, and are then used to generate a domain object model with objects drawn from the entities of the business as mentioned in the use cases. This is then converted into an analysis model by classifying the domain objects into three types: interface objects, entity objects, and control objects.

The big danger with OOSE is the assumption that you can express all sequences and business in use cases. Several major authors have subsequently declared that for many complex systems and almost all expert systems, it cannot be done. However, the use-case descriptions and their corresponding interaction diagrams can provide a very useful view of many parts of a system, and Objectory and OOSE have a good, simple notation.

The use-case analyses are easier to review with end users than is much of the output from other OO analysis methodologies; and use cases use narrative descriptions in plain English and are much easier to review with individuals who are not OO experts than are object models with object interaction diagrams.

SEOO is tightly integrated with Windows 4GLs such as PowerBuilder, and is perceived to be a very pragmatic and useful tool, but this perception may be due in part to a stronger marketing effort than is often made for nonproprietary methodologies. Because SEOO is proprietary, there is not as much detailed information available about it as there is about other methodologies, and it is somewhere between difficult and impossible to try it out just to compare it with the others.

A very positive aspect of this is the heavy focus on data management and data modeling. SEOO is intended to be object oriented while retaining the advantages of traditional data modeling. SEOO is unique in treating data, triggers, and referential-integrity rules as a set of shared objects in a database.

It treats a data model as a view of the shared objects, which also include constraints, rules, and dynamics state transitions and so on. SEOO draws a clear line between shared objects and other objects, and regards the shared objects as important interfaces between subsystems.

This technique allows a distinction, for example, between customer behavior shared by all applications and customer object behavior unique to a single application. It is a technique with which a purist would quibble, but which is eminently practical. It offers one of the most complete descriptions yet written of an OO analysis methodology.

Although it is somewhat lacking in OO design and construction, it contains a large number of ideas and approaches that are of significant use to analysts and designers. Rumbaugh starts by assuming that a requirements specification exists. For example, I recently drew a diagram of project deliverables in a proposal for a large OO development project using Visio and Rumbaugh notation to show the object hierarchy of deliverables which, at the first level of inheritance, included hardware, software, and printed deliverables.

Originally an object-based extension of data modeling, the Shlaer and Mellor methodology starts with an information model describing objects, attributes, and relationships. Note that this is more like a data model than an object model. Next, a state model documents the states of objects and the transitions between them.

Finally, a data-flow diagram shows the process model. This does not mean that it is not usable for such work, but the applications occasionally cited as examples of its use seem to be in the areas of real-time or process control.



Question:What do you mean by object modeling technique? Answer: The object modeling techniques is an methodology of object oriented analysis, design and implementation that focuses on creating a model of objects from the real world and then to use this model to develop object—oriented software. Now-a-days, OMT is one of the most popular object oriented development techniques. It is primarily used by system and software developers to support full life cycle development while targeting object oriented implementations. OMT has proven itself easy to understand, to draw and to use.


OOAD Object Modeling Techniques Q/A #1

Murn An interface is almost always attached to the class or component that realizes it. The class has methods that provide user interfaces by which the services provided by the class may be used. It depicts the behavior of objects undergoing a specific action series. An actor may be a person methodlogy.

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