in UML 2 0 Nicol Carissimi Summary whats

in UML 2. 0 Nicolò Carissimi

Summary • what’s behind UML: MDA • UML 2. 0 and MDA key concepts

what’s behind UML: MDA Model Driven Architecture • a specific software development approach (developed by the Object Managment Group) that shifts the focus from the “code” to the “model” and automatically keeps a relation between them • a MDA specification consists of: – a Platform Independent Model (PIM) – one or more Platform Specific Models (PSM), each describing how the base model is implemented on a different middleware platform • the mapping from a PIM to a PSM is implemented by tools • system's functionality and behavior are modeled once and only once UML is the language used for modelling

UML 2. 0 and MDA key concepts (1) two MDA’s key concepts guided the improvements over Uml 1 and its syntax and semantic: • Automation (of the software development process steps) – code generation – verification of software specifications – ability to execute abstract and incomplete models early in the development cycle – test cases generation • Abstraction (the essence of modelling) the ability to represent a complex system and all its components, with their architecture, behaviour and interactions

UML 2. 0 and MDA key concepts (2) improvements over Automation: • increased precision and consistency for complex modelling tools (no ambiguity) • more formal definition of the meaning of the modelling concepts and their mutual relationships improvements over Abstraction: • improved architecture modeling capabilities (distilled from existing architectural description languages and standards such as Acme, MSC 2000, SDL 2000 and UML-RT) with new diagrams, such as: – Component Diagrams – Composite Structure Diagrams • scalability (the ability to decompose structures at a hierarchical level to an arbitrary level of complexity), with the possibility to refer components’ architecture and interaction defined in separated diagrams

Other UML 2. 0 features • complete backward compatibility with UML 1. x • stronger integration between structure, behaviour and interaction diagrams • the language has become more complex, so UML 2. 0 has been modularized into a set of sublanguages, many of which are independent between each other

Summary • Sequence Diagrams in UML 2. 0 • • Interaction Frame Operators

Sequence Diagrams in UML 2. 0 two primary improvements: • “spec-ness”, the ability to specify things, which means less “natural-language notes” and consequently less ambiguity) • scalability, (here) the ability to reference interactions defined in separated diagrams, thus obtaining a kind of “nested” diagram organization (an interaction is the interplay of messages sent between objects over time for a specific purpose)

Interaction Frame (1) • What is it? basically, an interaction frame consists of some region of a sequence diagram that is divided into one or more fragments; each frame has an operator and each fragment may have a guard • How does it realize the aforementioned improvements? • “spec-ness” operators allow to formally express actions which, in UML 1, could only be expressed with the use of notes written in natural language • scalability diagrams enclosed in a frame can be named and referred in other diagrams

Interaction Frame (2) op (operator): applied to the enclosed interaction(s) (some operators require arguments, such as diagrams names, parameters, constants and guards) op [: arguments] [ [guard] ] diagram name | interaction diagram name: needed if we want to refer to a diagram defined elsewhere [guard]: a boolean expression the interaction is executed according to the guard’s value interaction: a (fragment of a) sequence diagram (it can contain other frames) if we need to enclose more interactions, we’ll separate them with an outlined line (see next slide)

Interaction Frame (3) op [guard_1] interaction_1 … [guard_n] interaction_n this is another example of an interaction frame: • a set of interactions is divided by an outlined line • interaction_i is executed if guard_i is true in the next slides we’ll see the correct syntax for each operator, with its meaning and some examples

Sequence Diagrams: operators (1) sd: <diagram name> (parameters) it names the diagram contained in the frame parameters are optional (they can be used if the diagram behaves in different ways when it’s referred in different occurrences, see this example)

Sequence Diagrams: operators (2) ref it refers to a diagram defined elsewhere with the sd operator the name of the referred diagram is specified in the middle of the frame (with optional parameters closed within round brackets if the referred diagram needs them)

Sequence Diagrams: operators (3) loop minint, maxint [guard] (think of it as the “for” or “while” statements) minint: the interaction must loop at least this number of times maxint (optional): the interaction may not loop more than this number of times [guard] (optional): after the first minint iterations, the condition is tested before each additional loop iteration: if the condition is false, then the loop is abandoned

Sequence Diagrams: operators (3) break if the selected interaction occurs, the enclosing interaction (in the example below, the one contained by the loop frame) is abandoned

Sequence Diagrams: operators (4) alt it selects one interaction to be executed from a set of interactions the selected interaction follows a true [guard] condition or an [else] condition if none of the guard conditions are true (think of it as the “case” of “if” statements); guards are specified over the lifeline of the object which eventually contains the evaluated variable(s)

Sequence Diagrams: operators (5) opt the enclosed interaction occurs only if [guard], specified over the lifeline of the object which eventually contains the evaluated variable(s), is true

Sequence Diagrams: operators (6) NOTE: actually the standard gives only a brief description of the following operators and does not provide an intuitive explanation of their meaning or usage. assert the selected interaction must occur exactly in the indicated way, if it doesn’t, you have an invalid interaction see http: //www. pst. informatik. uni-muenchen. de/personen/stoerrle/V/CSDUML. pdf for some possible interpretations region the enclosed interaction is a critical region, no other messages can interleave; a critical region is needed when a shared resource is updated to prevent the updates from overlapping and producing inconsistent results; you would typically use this within parallel interactions

Sequence Diagrams: operators (7) neg the enclosed interaction is invalid and can’t occur (it can be used, for example, to model a use case extension which ends with failure) see http: //www. pst. informatik. unimuenchen. de/personen/stoerrle/V/CSDUML. pdf for some possible interpretations par this operator indicates several interactions that may run concurrently (overlapped in time) seq partial ordering, “weak” strict ordering

References • • • UML 2 Sequence Diagram Overview http: //www. agilemodeling. com/artifacts/sequence. Diagram. htm by Scott W. Ambler UML 2. 0: Exploiting Abstration and Automation http: //www. sdtimes. com/opinions/guestview_098. htm by Brian Selic, IBM Rational Software Canada UML 2. 0 Incrementally Improves Scalability And Architecture http: //www. elecdesign. com/Articles/Index. cfm? Article. ID=5881 by Bruce Powel Douglas, ED Online “Architecting Systems with UML 2. 0” http: //www. uml-forum. com/out/pubs/IEEE_SW_Jul 03_p 57. pdf by Morgan Björkander and Cris Kobryn, Telelogic “UML 2. 0 For Dummies” by Michael Jesse Chonoles and James A. Schardt Ed. Hungry Minds © 2003

Sequence Diagrams: sd operator the diagram Fare_Fase has an input parameter f which makes the sequence diagram behave in different ways according to it’s value << back