MTAT Software Engineering Management

Transcription

1 MTAT Software Engineering Management Lecture 03: Principles of Software Process Modeling (Part A) Dietmar Pfahl Spring

2 Announcements Full project description now available on course wiki: - Short Presentations: Wednesday, 25 March Industry guest lecture on Monday, 23 March: Increasing the predictability of software delivery with lean processes by Marek Laasik (VP Engineering, Fortumo) Proposal for final exam dates: - Exam 1: Wednesday, May 27, 14:15-16:00 - Exam 2: Monday, June 01, 12:15-14:00

3 Structure of Lecture 03 Introduction to Process Modelling Exercise 2

4 What is a (Software Development) Process? A Process defines Who is doing What, When and How to reach a specific goal. In software engineering the goal is to build a software product or to enhance an existing one and by the way An effective process facilitates efficient development of software with the required quality reduces risk and increases predictability promotes common vision and culture

5 Product Quality vs. Process Quality When software delivers incorrect results we do not modify the results but the software that produces them. When a process delivers incorrect products then common practice is to (only) modify the products, instead of the process.

6 Software Development Challenges Product quality poor... but what should we change to fix this? e.g., when/how do we introduce defects and when/how should we find them? Deadlines missed... but where do we lose all that time? e.g., do we lose most time during requirements negotiation, or during testing? (unit testing? system testing? regression testing?) Budget overruns... but what are the most expensive activities? e.g., are we spending most effort on coding or on rework/refactoring? Overhead... do we spend much effort on non-productive activities? e.g., how much effort is spent for collecting information (manually)? New employees... how should they learn how we work?... e.g., through trial and error or by more efficient means?

7 Information Needs What information do we need to answer the questions on previous slide: Which activities are performed in which sequence? Which are the inputs and outputs of these activities? Who is involed in a specific activity? What techniques/tools should be used? How long does it (typically) take to complete an activity?... How can we gather and maintain this information? We can ask experienced professionals or we need precise and concise descriptions of the processes holding the required information! Cf. Paper on Root-Cause-Analysis (on course wiki)

8 Perceived Causes of Software Project Failures An Analysis of their Relationships by Timo O.A. Lehtinen, Mika V. Mäntylä, Jari Vanhanen, Juha Itkonen, Casper Lassenius, Department of Computer Science and Engineering, School of Science, Aalto University Causes and causal relationships in case Defect

9 Questions 1. What s the difference between Process and Process Model? 2. Is it possible to have no process in place?

10 Process versus Process Description Lee Osterweil, Software are Processes too (ICSE 1986): While a process is a vehicle doing a job, a process description is a specification of how the job is to be done. Thus cookbook recipes are process descriptions while the carrying out of the recipes are processes. A Process Model is a (semi-) formal representation of a Process Description

11 What are the Goals of Process Modeling? To enable effective understanding and communication At one development site (developers, teams,...) Between development sites (distributed development, outsourcing, contractor-supplier relations,...) To support project management Transparency, tracking,... To guide the developers Incorporating new employees To improve software development practice Improving processes requires measurement and measurement requires defined processes Evolving processes To support reuse of process knowledge Organsational learning To support automatic process enactment Workflow support

12 Processes Types of Process Models Product-Engineering Processes Engineering Processes Process-Engineering Processes Non-Engineering Processes Business Processes Social Processes Process Modeling Processes Software Knowledge Development Processes Maintenance Processes Project Mgmt Processes Quality Mgmt Processes Measurement Processes Improvement Processes Product Line Processes Conf Mgmt Processes Product Models... Quality Models Process Models Process Taxonomy Business Process Models... Social Process Models Engineering Process Models Life Cycle Models Life Cycle Models describe (classes of) activities of development processes at a high level of abstraction Technical Process Models Managerial Process Models Process Engineering Proc. Models

13 What is a (Software) Process Model? Software Process Model: An abstract software process description. It can be more or less formal. [Lonchamp 93] Key elements:

14 Characterization of Process Models A Process Model defines: an identifiable activity or a group of activities or a hierarchy of activities the sequence/order of activities (-> control flow) the input/output products (artifacts) of activities (-> product flow) the resources (roles and tools/techniques/methods) needed the relations between activities, artifacts and resources

15 Process Model Notation (Graphical)

16 Definition: Process Performer, Owner, Engineer Process Performer or Agent (PA) := Person/Agent who enacts/executes the process in order to achieve the process goal(s) Humans interpret process scripts, machines interpret process programs Process scripts and process programs are user-specific process descriptions Process Owner (PO) := Person or organizational entity that sets the goals of a process and is responsible for its achievement The PO provides resources for the enactment/execution of the process, but s/he is not responsible for providing process definitions Process Engineer (PE) := Person who has to fulfill one or several goals of process modeling (e.g., process definition to guide developers) To that end, the PE uses process models, which s/he defines, extends, improves, and manages The PE should pay attention to the accuracy of the model, i.e., the correspondence between real-world process enactment/execution and process model

17 Example of a Process Script (textual representation) Note: Process descriptions for humans can be enhanced by graphical representations and be made accessible in the form of: Handbooks, Electronic Process Guides (web-guides with hyperlinks) and Wikis. (Excerpt taken from the ISPW-6 Software Process Example)

18 Typical Contents of Process Model Representations

19 Module developer Moderator Tester Quality assurer The Role Concept Examples of Role Activity Relations RASCI Matrix R = Responsible Roles A = Approve Role A role is in charge of one or more activities defined in one or more processes A role has defined competences & responsibilities Activities Module design Module coding Module review Module testing R R S, R S R A I S = Support C = Consult I = Inform Possible relationships between agents and roles 1 : 1 1 : m n : 1 n : m

20 Descriptive vs. Prescriptive Process Models How is it done? How should it be done?

21 Prescriptive vs. Descriptive Process Models Prescriptive Models (theoretical) Ideal Process (Assumed) best practice Often requires instantiation and detailing Deviations from real processes are likely Examples: waterfall, V- model, spiral model, incremental, iterative, evolutionary, agile process models Descriptive Models (empirical) Accurate elicitation of actual, real processes Basis for the revision of existing (prescriptive) process models based on observation and experience

22 Relationship between Descriptive and Prescriptive Process Modeling

23 The Four Domains Principle [Source: Heidrich, Münch, Verlage: Process Modeling, Lecture at Uni KL, Summer 2012, Chapter 1] (Model)

24 Structure of Lecture 03 Introduction to Process Modelling Exercise 2

25 Exercise 2 Handout Task: Read the textual description of the process of surveying Customer Satisfaction using the Kano-Model Form a pair with a student sitting next to you and create a process model of the process of surveying Customer Satisfaction using the Kano-Model, i.e. Identify activities, artifacts, roles, tools/techniques/methods, and the relations between these entities Use either the graphical or the table notation shown on the next slide Give the resulting model to the course instructor

26 Exercise 2 (cont d) Process Model representations: Using product-flow notation Programm er uses consumes Design Implement Java Development Environment uses Activity Artifact Role produces Using table notation Method / Tool Code

27 The Kano-Model Customer Satisfaction high Excitement (Differentiation) Five dimensions of quality: Basic quality satisfies basic musthave needs which probably do not even need to be specified. Linear (Competitive) Competitive quality - satisfies expressed needs (usually in requirement specification). Performance high Basic (Cost of Entry) Excitement quality - satisfies latent needs, needs which are there but which the user hasn t expressed and/or is himself/herself aware of --- Indifference quality - needs which are covered but which user is indifferent to Reverse quality - qualities which the customer do not want

28 Next Lecture Topic: Principles of Process Modeling (Part B) For you to do: Send me the result of Exercise 2 (if not yet done) as soon as possible Read Project Description (cf. course wiki)