Visualizing Architectures INF 123 – Software architecture 1

Outline Some theory The tools Examples – Socket networking in the Linux kernel – Vivox: VOIP for Second Life 2

SOME THEORY 3

Software Architecture The set of most important design decisions “Most important” – According to the stakeholders “Design decisions” – Aware of the options – Also called constraints – More than just the code structure 4

Architectural Model Aka architectural view A subset of the design decisions Focused on a particular concern – Separation of concerns! MASC! Examples – Server-side of an online game – How the Linux kernel handles networking – Authentication process 5

Architectural Model 6 Architecture A visualization of the model “protect an entrance”

How do we choose what to model? Stakeholders decide – What should be modeled/modelled Components, connectors, configurations, rationales, constraints, behaviors, non-functional requirements, … – At what level of detail – At what level of fidelity More faithful = more expensive to maintain 7

Example: level of detail (few details) 8

More details 9

Inconsistent models Models contradicting each other 10

Reasons for inconsistencies Architects with different opinions Level of detail – High-level view has components absent in a lower- level view Static vs dynamic concerns – Component structure != protocol Functional vs non-functional concerns – Broadcast the message to everyone vs scalability Physical vs logical concerns – 2 self-contained subsystems for 3 machines 11

Visualizing models A model is abstract – Abstraction! MASC! A visualization must allow… – Architects to present their models – Stakeholders to discuss the models A visualization is concrete 12

TOOLS 13

Describing a Software Architecture “Just look at the source code!” Natural language – Easy to discuss and contract-like, but long to read XML, JSON – Good for hierarchical structures, but hard to read Images/screenshots – Good for usability arch, not for system or deploy Box-and-arrow diagrams – Back and forth with XML/JSON 14

Natural language The system has 3 components: C1, C2, and C3. C1 receives inputs from the user and forwards them to C2. C1 also receives information from C2 and displays it to the user. C2 … 15

XML 16 <types:archStructure xsi:type=”types:ArchStructure” types:id=”ClientArch”> Client Architecture <types:component xsi:type=”types:Component” types:id=”WebBrowser”> Web Browser <types:interface xsi:type=”types:Interface” types:id=”WebBrowserInterface”> Web Browser Interface inout <types:archStructure xsi:type=”types:ArchStructure” types:id=”ClientArch”> Client Architecture <types:component xsi:type=”types:Component” types:id=”WebBrowser”> Web Browser <types:interface xsi:type=”types:Interface” types:id=”WebBrowserInterface”> Web Browser Interface inout

JSON 17 xArch{ archStructure{ id = “ClientArch” description = “Client Architecture” component{ id = “WebBrowser” description = “Web Browser” interface{ id = “WebBrowserInterface” description = “Web Browser Interface” direction = “inout” } xArch{ archStructure{ id = “ClientArch” description = “Client Architecture” component{ id = “WebBrowser” description = “Web Browser” interface{ id = “WebBrowserInterface” description = “Web Browser Interface” direction = “inout” }

Screenshots 18 Static, 1pt Slow, 70pts Fast, 12pts

Box and Arrow The most appropriate most of the time UML Other standard diagrams 19 Logic State Display

UML Structure – Class diagram – Component diagram Interaction – Communication diagram – Sequence diagram Behavior – State machine – Flowchart/Activity diagram 20

Other standard diagrams Control flow graph Data flow diagram Swimming lane diagram 21

Your own diagrams Use the same symbol for the same things Use standard symbols and representations Don’t use the same symbol for different things Add a legend if needed 22 Client 1Client 2 Send position Has a 2-way connection server

Tools for diagrams Dia – Not just UML ArgoUML Eclipse UML plugins Visio, PowerPoint Gliffy, Lucidchart, online tools Paint (please don’t …) 23

EXAMPLE: SOCKET NETWORKING IN THE LINUX KERNEL 24

Swimming lane diagram 25

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Flowchart 27

Data flow diagram 28

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VIVOX: VOIP FOR SECOND LIFE 31

High-level diagram 32 Why is Vivox a separate server process?

Separation of concerns! 33 Down! Still working. But chat is down. Still working Chat is down 

Sequence diagram without Vivox 34

Sequence diagram with Vivox 35 Client-side Server-side

Client-side protocol 36

Class diagram (sort of) 37

Component diagram 38

Communication diagram 39

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