Control Hierarchy
13.4.5 Control Hierarchy
XRef
Control hierarchy, also called program structure, represents the organization of pro-
A detailed discussion of architectural styles and
gram components (modules) and implies a hierarchy of control. It does not represent patterns is presented in
procedural aspects of software such as sequence of processes, occurrence or order Chapter 14.
of decisions, or repetition of operations; nor is it necessarily applicable to all archi- tectural styles.
Different notations are used to represent control hierarchy for those architectural styles that are amenable to this representation. The most common is the treelike dia- gram (Figure 13.3) that represents hierarchical control for call and return architec-
If you develop object- tures. 4 However, other notations, such as Warnier-Orr [ORR77] and Jackson diagrams oriented software, the
[JAC83] may also be used with equal effectiveness. In order to facilitate later discus- structural measures
sions of structure, we define a few simple measures and terms. Referring to Figure noted here do not
13.3, depth and width provide an indication of the number of levels of control and apply. However, others
(considered in Part overall span of control, respectively. Fan-out is a measure of the number of modules Four) are applicable.
that are directly controlled by another module. Fan-in indicates how many modules directly control a given module.
4 A call and return architecture (Chapter 14) is a classic program structure that decomposes func- tion into a control hierarchy where a “main” program invokes a number of program components, which in turn may invoke still other components.
PA R T T H R E E C O N V E N T I O N A L M E T H O D S F O R S O F T WA R E E N G I N E E R I N G
The control relationship among modules is expressed in the following way: A mod- ule that controls another module is said to be superordinate to it, and conversely, a module controlled by another is said to be subordinate to the controller [YOU79]. For example, referring to Figure 13.3, module M is superordinate to modules a, b, and c. Module h is subordinate to module e and is ultimately subordinate to module M. Width-oriented relationships (e.g., between modules d and e) although possible to express in practice, need not be defined with explicit terminology.
The control hierarchy also represents two subtly different characteristics of the software architecture: visibility and connectivity. Visibility indicates the set of program components that may be invoked or used as data by a given component, even when this is accomplished indirectly. For example, a module in an object-oriented system may have access to a wide array of data objects that it has inherited, but makes use of only a small number of these data objects. All of the objects are visible to the mod- ule. Connectivity indicates the set of components that are directly invoked or used as data by a given component. For example, a module that directly causes another mod- ule to begin execution is connected to it. 5
Parts
» The Concurrent Development Model
» SUMMARY Software engineering is a discipline that integrates process, methods, and tools for
» PEOPLE In a study published by the IEEE [CUR88], the engineering vice presidents of three
» THE PROCESS The generic phases that characterize the software process—definition, development,
» THE PROJECT In order to manage a successful software project, we must understand what can go
» METRICS IN THE PROCESS AND PROJECT DOMAINS
» Extended Function Point Metrics
» METRICS FOR SOFTWARE QUALITY
» INTEGRATING METRICS WITHIN THE SOFTWARE PROCESS
» METRICS FOR SMALL ORGANIZATIONS
» ESTABLISHING A SOFTWARE METRICS PROGRAM
» Obtaining Information Necessary for Scope
» An Example of LOC-Based Estimation
» QUALITY CONCEPTS 1 It has been said that no two snowflakes are alike. Certainly when we watch snow
» SUMMARY Software quality assurance is an umbrella activity that is applied at each step in the
» R diagram 1.4 <part-of> data model; data model <part-of> design specification;
» SYSTEM MODELING Every computer-based system can be modeled as an information transform using an
» Facilitated Application Specification Techniques
» Data Objects, Attributes, and Relationships
» Entity/Relationship Diagrams
» Hatley and Pirbhai Extensions
» Creating an Entity/Relationship Diagram
» SUMMARY Design is the technical kernel of software engineering. During design, progressive
» Data Modeling, Data Structures, Databases, and the Data Warehouse
» Data Design at the Component Level
» A Brief Taxonomy of Styles and Patterns
» Quantitative Guidance for Architectural Design
» Isolate the transform center by specifying incoming and outgoing
» SUMMARY Software architecture provides a holistic view of the system to be built. It depicts the
» The User Interface Design Process
» Defining Interface Objects and Actions
» D E S I G N E VA L U AT I O N
» Testing for Real-Time Systems
» Organizing for Software Testing
» Criteria for Completion of Testing
» The Transition to a Quantitative View
» The Attributes of Effective Software Metrics
» Architectural Design Metrics
» Component-Level Design Metrics
» SUMMARY Software metrics provide a quantitative way to assess the quality of internal product
» Encapsulation, Inheritance, and Polymorphism
» Identifying Classes and Objects
» The Common Process Framework for OO
» OO Project Metrics and Estimation
» Event Identification with Use-Cases
» SUMMARY Object-oriented analysis methods enable a software engineer to model a problem by
» Partitioning the Analysis Model
» Designing Algorithms and Data Structures
» Program Components and Interfaces
» SUMMARY Object-oriented design translates the OOA model of the real world into an
» Testing Surface Structure and Deep Structure
» Deficiencies of Less Formal Approaches 1
» What Makes Cleanroom Different?
» Design Refinement and Verification
» SUMMARY Cleanroom software engineering is a formal approach to software development that
» Structural Modeling and Structure Points
» Describing Reusable Components
» SUMMARY Component-based software engineering offers inherent benefits in software quality,
» Guidelines for Distributing Application Subsystems
» Middleware and Object Request Broker Architectures
» An Overview of a Design Approach
» Consider expert Web developer will create a complete design, but time and cost can be appropriate
» A Software Reengineering Process Model
» Reverse Engineering to Understand Data
» Forward Engineering for Client/Server Architectures
» SUMMARY Reengineering occurs at two different levels of abstraction. At the business level,
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