Document object model

Document Structure. In addition, the content within a Web page can also be organized in a tree structure format, based on the various HTML and XML tags within the p>age. Mining efforts have focused on automatically extracting document object model (DOM) structures out of documents (Wang and Lui, 1998 Moh et al, 2000). 

Objects and snapshots are concrete depictions, and we will make good use of them in the chapters ahead, but each one shows only a particular situation at a given moment in time. To document a model properly, we need a way of saying what all the possible snapshots are. This is what type diagrams are for (see Figure 2.5). 

Parts II, III, and IV cover basic techniques for modeling with objects and advanced techniques for factoring and then recombining models and designs using packages, frameworks, and components. They do not describe a development process the steps to validate and document these models. 

Use case specifications document functional requirements. The next step is to design the partial system that the current iteration is supposed to deliver. The gap between requirements and design is not trivial, and a bridge between the two is desired. This bridge is what object-oriented analysis is about. The domain analysis object model is not the final design. However, it provides a starting point for the design process. 

All documents, hardware units, and software programs must be uniquely identified. It is not necessary to violate warranty seals in order to uniquely identify subcomponents. However, in situations where hardware units and software programs do not have a unique identification, physical labels and software header information can be added retrospectively. Unique identification should include the model number for hardware and the version number for software (e.g., MS Windows 2000 Professional Service Pack 2). Current approved versions of source code must correspond to current approved versions of software documents, object code, and test suites. All source code should have associated documentation. 

Microsoft Office allows the option to record macros for performing repetitive tasks. Although macros are somewhat limited for the development of true VBA applications, macro recording can be used effectively to learn VBA or create templates of code that can be generalized with the addition of variables. If VBA for Microsoft Office is enabled, you only need to press alt-fi i to open the VBA Integrated Development Environment (IDE). A search of the on-line help for Application Object will provide an interactive object hierarchy that describes (with detailed code examples) each object or collection. There are literally thousands of objects within the Microsoft Office application object models. Another very useful tool within the VBA environment is the Object Browser, which can be invoked with the F2 key. The Object Browser can be particularly useful to learn the objects of external components that have been referenced from within VB or VBA. This method is an excellent way to get started with new object types and follow along with the documentation. An example is shown in Figure 18.3 from the Excel 2000 VBA IDE. In this example, the Excel is the automation client and Sciex Analyst method component... 

Component Object Model (COM) is an object-oriented system for creating binary software components that can interact. COM is the foundation technology for Microsoft s OLE (compound documents) and ActiveX (Internet-enabled components). 

The whole object model can be serialized into a human-readable W3C-conform document, which can in turn be read and written by Hybrex WEB. 

The Universal Modeling Language is used to describe a software system [4, 5], Several kinds of diagrams exist to model the diverse properties of the system. Thus a description of the system can be developed that enables the systematic and uniform documentation of the system. The class diagram, for example, represents the classes and their relationships. But also interacting diagrams exist, to describe the dynamic behavior of the system and its objects. 

Object-oriented development (OOD) bases the software structure on a model of the users world within which the software will work. One benefit is that when the users talk in their own vocabulary about changes in their requirements, it is easier to see which parts of the software are relevant. The mirroring is not always exact—because of the constraints of platform, performance, and generalization—but if the differences are localized and clearly documented, the benefits of OOD are not lost. 

The same model of object types and attributes could describe situations in the real world, for a software specification, or even of code. Section 2.6 introduces the dictionary as a mechanism for documenting the relationship between model elements and what they represent. 

Whereas snapshots illustrate specific sample situations, what we need to document are the interesting and allowed states the objects, links, and labels that will be used in the snapshots. This documentation is the purpose of a static model, which comprises a set of type diagrams and surrounding documentation. 

A model of object state is used to define a vocabulary of precise terms on which to base an analysis, specification, or design. A well-written document should contain plenty of narrative text in natural language along with illustrative diagrams of all kinds, but the type models are used to make sure that there are no gaps or misunderstandings. More on this in Chapter 5, Effective Documentation. 

Specifications A specification describes actions using postconditions (perhaps drawn with state charts) the postconditions are written in terms of a vocabulary of objects and their static relationships, which is described in a type model. These documents must be inspected at external design reviews. Types, rather than classes, are the main focus. 

In other cases, there is no strong need to construct a business model before you get on with a component spec, particularly if the software focuses on only one aspect of a very general business. Sometimes it is useful to create the static part of the business model, without any collaborations. For example, before designing a word processor, you first define what a document is. This is the business world in this case—the subject matter with which the software will deal but modeled separately from any concerns of what the software will do with it. This approach is particularly useful when there are standards of interchange between components Web pages, RTF files, floppy disks, and TV pictures all have standard models of the objects without designing the equipment that handles them. 

Business model A (section of a) document that describes the business or problem domain, precisely capturing object types, attributes, invariants, and actions. This document may itself be structured based on... 

We describe designs for objects using collaborations—collections of actions. A joint action defines a goal achieved collaboratively between the participant objects, using postconditions whose vocabulary is the model of each of the participants. Collaborations range from business interactions ( banks trade stocks ) to hardware ( fax sender sends document to receiver ) to software ( scrollbar displays file position ). 

The attributes of a complex object are usually expressed in terms of types, which themselves are modeled with other attributes and so on. Drawing them pictorially shows the relationships more clearly. When an object is specified, the types of attributes are chosen for their expressiveness rather than for execution efficiency. Some of these specification types invented to help model a set of actions may never be implemented directly however, the type model must constitute a valid abstraction of the implementation, as documented in a refinement and its justification. The types that are implemented are those generated by decomposition they must exist because the design calls for them to interact with one another. 

Model the business by drawing the glossary explanations in pictures. Ensure that every concept written in documents that describe the business, or uttered by experts in the business, is represented somewhere. Generally, nouns map to object types, and verbs map to actions. 

Documenting a type specification involves describing the relevant actions an object participates in, and expressing the effect of those actions in terms of a type model of that object. The specification should be satisfied by any correct implementation, and the type model is an abstraction of any correct implementation. 

Summarise the interactions with the system as collaborations between the system being specified and other objects, building scenarios to validate the collaboration, and modeling actions at a consistent level of abstraction. Show all external roles as types — also called actors — that participate in these actions. Also, document those actions that can proceed concurrently on a single system, including constraints on concurrency. For example ... 

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