Objects, components, and Frameworks with UML Catalysis Objects, components, and Frameworks with UML Catalysis/Testing

From the book Objects, components, and frameworks with UML: the Catalysis Approach, by Desmond D’Souza and Alan Wills. Catalysis/Testing

A tour Objects and actions object: cluster of information + functionality action: anything that happens actions can be independent of objects. Bound to objects later. what happens during action which object is responsible for doing action which object is responsible for initiating action how is it done actions affect objects Catalysis/Testing

Fractal picture A fractal picture has the same appearance at all scales objects: business departments, machines, running software components, programming language concepts actions: interactions among objects: big business deals,phone calls, bike rides, etc. Catalysis/Testing

Actions affect objects Actions = collaborations In Catalysis collaborations are first-class units of design. Where should collaborations be used? what goes on inside a software component user-component interactions business modeling: how do real-world objects interact? Catalysis/Testing

Actions affect objects Actions have participants (objects) Which objects do you need? Enough to describe the actions Associations provide a vocabulary in which it is possible to describe effects of actions (prefer: class graph over associations) Catalysis/Testing

Precise specifications action(student,teacher):: teach(skill) post student.accomplishments = student.accomplishments@pre+ skill Catalysis/Testing

Refinement Of objects and actions Zoom in and out Catalysis/Testing

Connection to aspectual components objects, components (actions), connectors actions have a modification interface Catalysis/Testing

Commonalities Catalysis/AC actions independent of objects abstract does not mean fuzzy program should be structured according to a business model static model AC independent of objects AC is abstract and executable program should look like a design participant graph Catalysis/Testing

Differences Catalysis/AC actions cannot describe aspects uses pre- and post-conditions no connectors AC (when modification interface is used) can model aspects should use pre and post conditions connectors keep components clean Catalysis/Testing

Development Layers: vanilla development from scratch Business model (domain/essential model) Requirements specification Component design Object design Component kit architecture: needed to build interoperable components April 11,99 Catalysis/Testing

Static models and invariants An action’s postcondition can be written in terms of static relationships Connection: participant graph of AC contains information to describe postconditions Catalysis/Testing

Model Frameworks as Templates Similar to AC, but no aspects parameterized Catalysis/Testing

Requirements Specification Models Objects in this diagram are not real objects but rather the system’s own representation of them Static model: is a hypothetical picture created for explaining the systems externally visible behavior to its users. Catalysis/Testing

Static model (continued) There is no mandate on the designer to implement it exactly with classes and variables that mirror directly the types and associations in the spec. Catalysis/Testing

Partitioning the model between components Each of the components performs only some of the system’s functions and includes only part of its state different vocabulary; need map reconstruct all the attributes and associations from component design Catalysis/Testing

Collaborations Now: a collaboration is a collection of actions and the types of objects that participate in them Sometimes they say: action = collaboration Catalysis/Testing

Testing When does a more detailed design conform/implement/refine a more abstract one? How to test different kinds of refinement relations? Connection: refinement/testing Catalysis/Testing

Testing Pre and post conditions useful for testing test harness C++ STL library: has assert macro Every component needs to have its own test kit to monitor behavior in new context Catalysis/Testing

Retrieval functions Every implementation should have a complete set of retrieval functions; that is, read only abstraction functions for computing the value of every attribute in the spec. from the implementation Need to translate from one model to another Retrieval functions can be inefficient: only used for verification; e.g. testing. Catalysis/Testing

Retrieval functions Long history: VDM, Z support traceability: how change in spec or code influences the other use retrieval diagrams Catalysis/Testing

Benefits of retrieval functions cross-check make it explicit how abstract model is represented in the code testing: execute postconditions and invariants defined in requirement model Catalysis/Testing

Golden rule of OOD Choose your classes to mirror your specification model. 1-1 correspondence often not possible model that gives best performance often different from one that clearly explains what the object does multiple models are implemented simultaneously: each model: partial view Catalysis/Testing

Testing by adapting the implementation Specification (with test information) Implementation package Adapter Implementation Catalysis/Testing

s.value = s.left.content.value + s.right.content.value Spreadsheet Content * Cell content shows value right left Sum Number Blank Invariants: for all Sum objects s: s.value = s.left.content.value + s.right.content.value for all Blank objects b: b.value = 0 Simplified: a formula can be only the sum of two other cells Catalysis/Testing

RETRIEVAL DIAGR. Sum s; s.left = s.impl1.operands[1].abs Spreadsheet Content * Cell content shows value abs Sum s; s.left = s.impl1.operands[1].abs s.right=s.impl1.operands[2].abs s.value=s.impl1.container.value right left Sum Number Invariants: for all Sum objects s: s.value = s.left.content.value + s.right.content.value for all Blank objects b: b.value = 0 abs Blank abs RETRIEVAL DIAGR. impl1 Spreadsheet_1 impl1 impl1 * sumpart Cell_I shows container Sum_I isBlank:boolean value * operands Catalysis/Testing

Retrieval functions with DJ How to represent the participant graph? Use strategy graph. Introduce a string for each edge. E1 = “{A->B bypassing X}”. class A {B getB(){return (B) tg.fetch(this);} } tg is the traversal graph for E1. Catalysis/Testing

Retrieval functions Overlay concrete class graph with participant class graph using getter functions that are implemented using strategies. Name map is identity map. Can simplify class graph before writing strategies. Can introduce multiple class graph views. Catalysis/Testing

S is participant graph for G F=t F D D E E B B C C S G A = s A

Catalysis Process: Main Theme Higher-level Lower-level, a refinement of higher level. Retrieve mapping from higher-level to lower-level. For every specification activity there is a corresponding implementation and testing activity Catalysis/Testing

Typical Process for a Business System Requirements System Specification Architectural Design: components/connectors application architecture: packages, collaborations technical architecture: hardware, software platform, infrastructure components Component Internal Design Catalysis/Testing

Typical Project Evolution : page 522 The business case: initial requirements Domain or business model: independent of software solution. Reusable across multiple projects. Joint-Application Development: developers/users Glossary Catalysis/Testing

Typical Project Evolution Type model plus system specifications. Primary actions system participates in. Refined to atomic interaction with system. UI sketches Subject areas Generic problem frameworks Refactor for reuse Catalysis/Testing

Typical Project Evolution Design rules for technical architecture Technical architecture model Horizontal slices: architecture simulation Application architecture: design of application logic as a collection of collaborating components Project plan, deployment Catalysis/Testing

Chapter 3: Behavior Models Component-based software development: separate external behavior from internal implementation Describe behavior: by list of actions and response to those actions (called the component’s type) Catalysis/Testing

Two parts of a specification Static model (structure): UML class diagram and invariants Type specification (behavior): specify effects of actions on component using vocabulary provided by static model This chapter: about how to derive and write type specifications. Examples follow. Catalysis/Testing

Static model with behavior Course Scheduling staff fullSchedule * * Static model instructor 0..1 Client Session Instructor sessions * grade: Grade date : Date * sessions rating: Grade client {ordered date} Invariant (business rule): fullSchedule.grade <=fullSchedule.instructor.rating checkAvailability(instructor,date) post: find whether instructor is doing a session on that date scheduleCourse(date,client) post: set up a new session and assign an instructor behavior Behavior defined in terms of static model Catalysis/Testing

Static Model find all persons waiting at any bus stop on a bus route busStops BusRoute BusStop 0..* DOES NOT REVEAL TOO MANY IMPLEMENTATION DETAILS waiting 0..* Person Catalysis/Testing

Implementation 1 find all persons waiting at any bus stop on a bus route busStops BusRoute BusStopList OO solution: one method for each red class buses 0..* BusStop BusList waiting 0..* passengers Bus PersonList Person 0..* Catalysis/Testing

find all persons waiting at any bus stop on a bus route Implementation 2 villages BusRoute BusStopList buses VillageList busStops 0..* 0..* BusStop BusList Village waiting 0..* passengers Bus PersonList Person 0..* Catalysis/Testing

Filter out noise in class diagram only three out of seven classes are mentioned in static model BusRoute BusStop Person explain why strategy better replaces traversal methods for the classes BusRoute VillageList Village BusStopList BusStop PersonList Person Catalysis/Testing

Map static model to application class graph villages BusRoute BusStopList VillageList busStops 0..* 0..* BusStop Village busStops BusRoute BusStop 0..* edge -> path Catalysis/Testing

Using DJ class BusRoute { Vector busStops(){return Main.cg.gather(this, new Strategy( “from BusRoute to BusStop”);} } Catalysis/Testing

Using DJ: complete solution class BusRoute { Vector waitingPersons(){return Main.cg.gather(this, new Strategy( “from BusRoute via BusStop to Person”);} } Catalysis/Testing

Notes Static model is translated into a strategy Why? With DJ behavior is written in such a way that it is usable in many different static models Catalysis/Testing

Two approaches Catalysis: Define static model and define behavior using static model Map static model to implementation model Behavior is in implementation model DJ: Define strategies corresponding to static model and express behavior using strategies. Adjust strategies for implementation model. Behavior is in implementation model Catalysis/Testing

Using DJ: complete solution Java problem: parameterization class BusRoute { Vector waitingPersons(){return Main.cg.gather(this,new Strategy( “from BusRoute via BusStop to Person”);} } Catalysis/Testing

Using DJ: complete solution Java problem: parameterization class BusRoute { PersonList waitingPersons(){return Main.cg.traverse(this,new Strategy( “from BusRoute via BusStop to Person”,new CollectionVisitor());} } Catalysis/Testing