OO Project Metrics and Estimation
20.4.2 OO Project Metrics and Estimation
Conventional software project estimation techniques require estimates of lines-of- code (LOC) or function points (FP) as the primary driver for estimation. Because an overriding goal for OO projects should be reuse, LOC estimates make little sense. FP estimates can be used effectively because the information domain counts that are required are readily obtainable from the problem statement. FP analysis may provide value for estimating OO projects, but the FP measure does not provide enough gran- ularity for the schedule and effort adjustments that are required as we iterate through the recursive/parallel paradigm.
CHAPTER 20
OBJECT-ORIENTED CONCEPTS AND PRINCIPLES
Lorenz and Kidd [LOR94] suggest the following set of project metrics: 6 Number of scenario scripts. A scenario script (analogous to use-cases dis-
These metrics can be cussed in Chapter 11) is a detailed sequence of steps that describe the inter- used to supplement
the FP metric. They action between the user and the application. Each script is organized into provide a way to
triplets of the form “size” an OO project.
{initiator, action, participant} where initiator is the object that requests some service (that initiates a mes-
sage); action is the result of the request; and participant is the server object that satisfies the request. The number of scenario scripts is directly correlated to the size of the application and to the number of test cases that must be developed to exercise the system once it is constructed.
XRef
Number of key classes. Key classes are the “highly independent compo-
A detailed discussion of nents” [LOR94] that are defined early in OOA. Because key classes are central OO metrics is presented
in Chapter 24. to the problem domain, the number of such classes is an indication of the amount of effort required to develop the software and also an indication of the potential amount of reuse to be applied during system development.
Number of support classes. Support classes are required to implement the system but are not immediately related to the problem domain. Examples might be GUI classes, database access and manipulation classes, and com- putation classes. In addition, support classes can be developed for each of the key classes. Support classes are defined iteratively throughout the recur- sive/parallel process.
The number of support classes is an indication of the amount of effort required to develop the software and also an indication of the potential amount of reuse to be applied during system development.
Average number of support classes per key class. In general, key classes are known early in the project. Support classes are defined through- out. If the average number of support classes per key class were known for a given problem domain, estimating (based on total number of classes) would
be much simplified. Lorenz and Kidd suggest that applications with a GUI have between two and three times the number of support classes as key classes. Non-GUI applications have between one and two times the number of support classes as key classes.
Number of subsystems. A subsystem is an aggregation of classes that sup- port a function that is visible to the end-user of a system. Once subsystems are identified, it is easier to lay out a reasonable schedule in which work on subsystems is partitioned among project staff.
6 Technical metrics for OO systems are discussed in detail in Chapter 24.
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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