Software Design, Modelling and Analysis in UML Modelling know the - PowerPoint PPT Presentation

Contents & Goals This Lecture: • Educational Objectives: After this lecture you should • be able to explain the term model . Software Design, Modelling and Analysis in UML Modelling • know the idea (and hopes and promises) of model-based SW development. • be able to explain how UML fits into this general picture. Lecture 1: Introduction • know what we’ll do in the course, and why . • thus be able to decide whether you want to stay with us... • Content: • Analogy: Model-based/-driven development by construction engineers. 2013-10-21 • Software engineers: “me too” – Model-based/-driven Software Engineering. • UML Mode of the Lecture: Blueprint. – 1 – 2013-10-21 – Sprelim – • Contents of the course – 1 – 2013-10-21 – main – – 1 – 2013-10-21 – main – Prof. Dr. Andreas Podelski, Dr. Bernd Westphal • Formalia Albert-Ludwigs-Universit¨ at Freiburg, Germany 2 /40 3 /40 Disclaimer An Analogy: The House-Building Problem (Oversimplified) Approach: Floorplan 2. Design • The following slides may raise thoughts such as: Given a set of Requirements , such as: 1. Requirements • The house shall fit on the given piece of land. • “everybody knows this”, • Each room shall have a door, the doors shall open. • “completely obvious”, 3. System • The given furniture shall fit into the living room. • Shall fit on given http://wikimedia.org (CC nc-sa 3.0, Ottoklages) piece of land. • “trivial”, • The bathroom shall have a window. • Each room shall • “clear”, have a door. • The cost shall be in budget. • Furniture shall fit • “irrelevant”, into living room. Wanted : a house which satisfies the requirements. • “oversimplified” • Bathroom shall have a window. • . . . Now, strictly speaking, a house is a complex system : • Cost shall be in http://wikimedia.org (CC nc-sa 3.0, budget. Bobthebuilder82) • Consists of a huge number of bricks. Which is true , in some sense, • Consists of subsystems, such as windows. • but: “everybody” is a strong claim, and I want to be sure that this holds • Water pipes and wirings have to be in place. – 1 – 2013-10-21 – Smodel – – 1 – 2013-10-21 – Smodel – – 1 – 2013-10-21 – Smodel – for the audience from now on. • Doors have to open consistently. In other words: that we’re talking about the same things. Observation : Floorplan abstracts from, e.g., . . . • Floors depend on each other (load-bearing walls). • kind, number, and placement of bricks, • water pipes/wiring, and • . . . • subsystem details (e.g., window style), How do construction engineers handle this complexity...? 4 /40 5 /40 6 /40

Approach: Floorplan Floorplan as an Abstraction What is it good for? Build by Plan. 2. Design γ • As said before, the floorplan abstraction α preserves some properties. all houses 1. Requirements For instance, we have: Room R has window in H if and only if R -representation in α ( H ) has window. 3. System • Shall fit on given • http://wikimedia.org (CC nc-sa 3.0, Ottoklages) F • And we have the general rule: piece of land. • If a house H ′ is (or: will have been) built according to plan F , and • Each room shall • • have a door. H if plan F has property φ , and if α/γ preserve this property, • Furniture shall fit then H ′ has (or: will have) property φ . into living room. • Bathroom shall have a window. α • So we can answer some questions about H • Cost shall be in http://wikimedia.org before even building it , e.g.: budget. (CC nc-sa 3.0, α Bobthebuilder82) • Bathroom shall have a window. • Shall fit on given piece of land. • Floorplan F denotes a set γ ( F ) of houses ( concretisations of F ), • Each room shall have a door. – 1 – 2013-10-21 – Smodel – – 1 – 2013-10-21 – Smodel – – 1 – 2013-10-21 – Smodel – which differ, e.g. in colour of bricks, or making of windows. • Furniture shall fit into living room. • Floorplan F represents house H according to abstraction α . Observation : Floorplan preserves , e.g., . . . • Cost shall be in budget. • house and room extensions (to scale), • placement of subsystems • By adding information to F (such as making of windows), • And: it’s typically easier (and cheaper) to correct errors in the plan, • presence/absence of windows and doors, (such as windows). we can narrow down γ ( F ) . rather than in the finished house. 6 /40 7 /40 8 /40 “Silver Bullet” or Can Anything Go Wrong...? Good for Anything Else? Documentation. What’s the Essence? • Given : a house. • If the requirements are already contradictory (or inconsistent ), then there is no sense in drawing a plan. • Wanted : a concise description for potential buyers. Definition. [Folk] A model is an abstract, formal, mathematical repre- sentation or description of structure or behaviour of a (software) system. Example : • Approach : draw a floorplan. • The house shall fit on the given piece of land. • The given furniture shall fit into the living room. Definition. [Glinz, 2008, 425] A model is a concrete or mental image (Abbild) of something or a concrete or mental archetype (Vorbild) for something. What if the land is 10m narrow and the couch is 11m × 11m? Three properties are constituent: (i) the image attribute (Abbildungsmerkmal), i.e. there is an entity (called original) whose image or archetype the model is, (ii) the reduction attribute (Verk¨ urzungsmerkmal), i.e. only those at- Distinguish : tributes of the original that are relevant in the modelling context – 1 – 2013-10-21 – Smodel – – 1 – 2013-10-21 – Smodel – – 1 – 2013-10-21 – Smodel – are represented, • Sometimes the plan F is first , and the realisation H ∈ γ ( F ) comes later . (iii) the pragmatic attribute, i.e. the model is built in a specific context • Sometimes the realisation H is first , and the “plan” F = α ( H ) comes later . for a specific purpose. 9 /40 10 /40 11 /40