BDSA08 Advanced Architecture

Transcription

1 UI Swing not the Java Swing libraries, but our GUI classes based on Swing Web Domain Sales Payments Taxes Technical Services Persistence Logging RulesEngine BDSA08 Advanced Architecture Jakob E. Bardram

2 Resumé on Architecture Architecture Design Logical Architecture & UML Package Diagrams Layers Architectural Analysis [OOAD] ch. 33 FURPS+ Quality Scenarios RUP phases & Architecture Logical Architecture Refinement [OOAD] ch 34 Layers Information Systems (IS) Today 2

3 Architecture Design 3

4 Software architecture The design process for identifying the sub-systems making up a system and the framework for subsystem control and communication is architectural design. The output of this design process is a description of the software architecture ~ SAD 4

5 Architectural design An early stage of the system design process. Represents the link between specification and design processes. Often carried out in parallel with specification activities. It involves identifying major system components and their communications. Advantages Stakeholder communication Architecture may be used as a focus of discussion by system stakeholders. System analysis Means that analysis of whether the system can meet its nonfunctional requirements is possible. Large-scale reuse The architecture may be reusable across a range of systems. 5

6 Architecture and system characteristics Performance Localize critical operations and minimize communications. Use large rather than fine-grain components. Security Use a layered architecture with critical assets in the inner layers. Safety Localize safety-critical features in a small number of subsystems. Availability Include redundant components and mechanisms for fault tolerance. Maintainability Use fine-grain, replaceable components. 6

7 System structuring Concerned with decomposing the system into interacting sub-systems. The architectural design is normally expressed as a block diagram presenting an overview of the system structure. Later as an UML Package Diagram More specific models showing how sub-systems share data, are distributed and interface with each other may also be developed. 7

8 Resumé of Architecture The software architecture is the fundamental framework for structuring the system. Architectural design decisions include decisions on the application architecture, the distribution and the architectural styles to be used. Different architectural models such as a structural model, a control model and a decomposition model may be developed. System organisational models include repository models, client-server models and abstract machine models. Modular decomposition models include object models and pipelining models. Control models include centralised control and event-driven models. 8

9 Logical Architecture and UML Package Diagrams 9

10 What is the Logical Architecture? The logical architecture is the large-scale organization of the software classes into packages (or namespaces), subsystems, and layers [p. 199] Note; it is logical since it does not address deployment A layer is a very coarse-grained grouping of classes, packages, or subsystems that has a cohesive responsibility for a major aspect of the SuD [p. 199] 10

11 Typical Layers (in an IS system) UI Swing not the Java Swing libraries, but our GUI classes based on Swing Web Domain Sales Payments Taxes Technical Services Persistence Logging RulesEngine 11

12 Software Architecture An architecture is the set of significant decisions about the organization of a software systems, the selection of the structural elements and their interfaces by which the system is composed, together with their behavior as specified in the collaborations among those elements, the composition of these structural and behavioral elements into progressively larger subsystems, and the architectural style that guides this organization these elements and their interfaces, their collaborations, and their composition. 12

13 UML Package Diagram UI Domain Swing Web Sales UI UI::Swing UI::Web Domain::Sales Swing Web Domain Sales 13

14 Horizontal and Vertical Layers Domain POS Inventory Tax Vertical Layers Technical Services Persistence Security Logging Horizontal Partitions 14

15 Architectural Analysis 15

16 Architectural Analysis Architectural Analysis is concerned with the identification and resolution of the system s nonfunctional requirements, in the context of the functional requirements Investigation ~ identification Resolution ~ design Variation points variations in the existing system (e.g. multiple tax calculation) Evolution points speculative point of variation that may arise in the future 16

17 Reliability and Fault-tolerance fail-over strategy? vulnerability to other systems failure? Licensing costs of purchased subcomponents build or buy? Adaptability and Configurability variations in business rules? configuration of POS terminals? Brand names and Marketing change name on system re-sell as an OEM solution? Examples 17

18 Architectural Factors ~ FURPS+ FURPS Functional Usability Reliability Performance Supportability + Implementation Interfaces Operations Packaging Legal 18

19 Quality Scenarios Quality Scenarios define measurable responses can be verified <stimulus><measurable response> Examples response time computer or human mean-time-to-failure time to integrate w. 3 rd party mean-time-to-recover load scalability... 19

20 Architectural Factor Table see example p. 548 Factor Measures and Quality Scenarios Variability Impact of factor on stakeholders Priority for Success Difficulty or Risk 20

21 Documentation Record and document architectural alternatives decisions motivations aka Rationale see example p

22 RUP Diciplines 22

23 Architectural Analysis and RUP Inception create architectural Proof-of-Concepts [OOAD] I prefer Architectural Prototype Elaboration major phase for doing architectural work do architectural analysis implement core risky architectural components factor table, technical memos, SAD completed Construction minor adjustments Transition review SAD update documentation 23

24 Logical Architecture Refinement 24

25 UI Layered Architectures Swing ProcessSale Frame not the Java Swing libraries, but our GUI classes based on Swing Text ProcessSale Console used in quick experiments Domain Sales Pricing Register Sale PricingStrategy Factory «interface» ISalePricingStrategy ServiceAccess Payments Services Factory CreditPayment «interface» ICreditAuthorization ServiceAdapter Inventory POSRuleEngine Taxes «interface» IInventoryAdapter POSRuleEngineFacade «interface» ITaxCalculatorAdapter Technical Services Persistence DBFacade Log4J Jess A general purpose thirdparty rules engine. SOAP 25

26 Dependencies Swing UI ProcessSale Frame Domain Sales Register Sale Pricing ServiceAccess Services Factory Payments CreditPayment «interface» ICreditAuthorization ServiceAdapter Inventory «interface» IInventoryAdapter POSRuleEngine POSRuleEngineFacade Taxes «interface» ITaxCalculatorAdapter Technical Services Persistence DBFacade Log4J Jess SOAP 26

27 Inter-package Interaction Scenarios UML notation: UML path name to indicate packaging UML notation: Note that a subsytem can be modeled as an object in the UML. This is useful in this case where I don't know or want to describe the details of how the Jess rule engine works, but just want to show collaboration with it. :Cashier : UI:: Swing:: Process SaleJFrame : Domain:: Sales:: Register : Domain:: Products:: Product Catalog s : Domain:: Sales:: Sale : Domain:: POSRule- Engine:: POSRule- Engine Facade 1 1 : Tech- Services:: Persistence:: Persistence- Facade «subsystem» : Tech- Services ::Jess enteritem (id, qty) enteritem (id, qty) desc = getproduct Desc(id) desc = getobject(...,id) makelineitem(desc, qty) onpropertyevent(s, "sale.total", total) x = isinvalid (lineitem, sale) somejesscalls(lineitem, sale) Points of crossing interesting boundaries or layers. These are especially noteworthy for people who need to understand the system, and thus are highlighted in this diagram. This diagram supports communicating the logical view of the architecture (a UP term) because it emphasizes architecturally significant information. 27

28 Package vs. Subsystem packages need not be subsystem subsystem is a (set of) package(s) Package vs. Subsystem «subsystem» POSRuleEngine not a subsystem POSRuleEngineFacade Pricing «subsystem» Persistence DBFacade «subsystem» Jess 28

29 Facade Pattern Often a subsystem is accesses through a Facade reveals functionality hides complexity and implementation details the only way to access the subsystem 29

30 Facade on a subsystem Swing UI ProcessSale Frame for applications with only a few system operations, perhaps only one object acts as the facade into the layer Domain Sales Register Sale The Technical Services layer typically exposes many interfaces--at least one per subsystem Technical Services Persistence DBFacade Log4J Jess SOAP 30

31 Session Facades UI Swing... ProcessSale JFrame ProcessRental JFrame Application ProcessSale SessionFacade ProcessRental SessionFacade HandleReturns SessionFacade Application session facade objects that maintain session state and control workflow related to some work--often by use case. Domain Sales Rentals Register Sale Rental... 31

32 Is the Application Layer Optional? The Application Layer mediates between the UI and Domain Layer implements the controller or the session facades responsible for knowing the session state of the clients May be omitted in simple applications But, always used in application like multiple user interfaces (e.g. web + GUI) distributed applications, i.e. where the App and UI layer are on different hosts when the domain layer cannot hold session state if there is a defined workflow (Activity Diagrams) 32

33 Information Systems Information Systems (IS) is the most well-known examples of layered architectures The classic Three-Tier Architecture Interface Application Logic Storage Int erf ace Application Lo gic Calculate taxes Authorize payme nts Storage Database 33

34 Deployment of Three-Tier Systems 2 nodes = Thick Client Visual Basic, PowerBuilder, Access,... CRUD = create, retrieve, update, delete 3 nodes = Thin Client Java, J2EE, C#.net Int erface Int erface UML notation: a node. This is a processing resource such as a computer. Application Lo gic calculate taxes Application Lo gic calculate taxes classic 3-tier architecture deployed on 2 nodes: "thicker client" classic 3-tier architecture deployed on 3 nodes: " thiner client" 34

35 Resumé on Architecture Architecture Design Logical Architecture & UML Package Diagrams Layers Architectural Analysis [OOAD] ch. 33 FURPS+ Quality Scenarios RUP phases & Architecture Logical Architecture Refinement [OOAD] ch 34 Layers Information Systems Today 35