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“Top-10” MBSE Tool Inspections to Analyze System Design Quality (a.k.a., “ We now have a system model…but… …how good is the model?”) Dr. Paul Montgomery Associate Professor of Systems Engineering Naval Postgraduate School 3 April 2014 2014 © 2014, Paul R. Montgomery 1 BLUF MBSE data-driven, system definition tools can provide keen insights into the quality of system design. Quality dimensions = 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Requirements Mission and operations and interoperability Functionality Interfaces and continuity System Content Flow System Logical control System Behavior System Realization, Allocation, and Integrity Integrate-ability Qualify-ability 2014 2 Top 10 MBSE Tool Inspections REFERENCE SYSTEM AND TOOL 2014 7 For Our Discussion Reference Systems • Various (from grad school projects) • Keep your eye on the structures vice the names Reference Tool • Vitech Corp – CORE® 2014 8 Top 10 MBSE Tool Inspections SYSTEM FOUNDATIONS (REQUIREMENTS & CONOP) 2014 9 1- System Requirements (1 of 1) • Requirements hierarchy and “spider” diagrams provides insight into requirements design beyond “requirements grammar” 2014 10 1 - System Requirements • Key inspections: • Hierarchy depth • Allocations • Orphans • Hierarchy depth indicates strength of requirements derivation ? ? • Requirements allocated to system functions/components sets foundation for qualification (V&V) 2014 11 2 – Mission, Operations and Interoperability • Key inspections: • 4 ICOM present • Sources/destinations • External system diagramming identifies critical interoperability interfaces • Sets framework for integration and qualification (validation/acceptance) strategy 2014 12 2 – Mission, Operations • and Interoperability Key inspections: • No Conop in the model CONOP must manifest into mission activities and data flow 2014 13 Top 10 MBSE Tool Inspections SYSTEM STRUCTURE (ARCHITECTURES) 2014 14 • Key inspections: • Hierarchy depth • Allocations • Orphans 3 - System Functionality ? ? ? •Hierarchy depth indicates functional design understanding and fidelity 2014 15 4 - System Interfaces / Continuity • Key inspections: • Ensure connection completeness • Don’t rush to this diagram too soon • Physical block diagramming (schematic is very familiar but easily overwhelming) 2014 16 4 - System Interfaces / Continuity • N2 diagramming is good tally of interfaces (both functional and physical) • Better “eye-ready” assessment 2014 17 4 - System Interfaces / Continuity • Key inspections: • N2 - “missing squares” • N2 - Vacant quadrant • N2 - Sparse matrix • N2 – Missing externals • N2 – High density I/O ? ? 2014 18 5 - System Content Flow •Key inspections: •IDEF0 – Disconnects “()” •IDEF0 – Missing ICOM ? ? ? 2014 19 6 - System Logical Control • Key inspections: • Linearity (usually not true) • Dynamic control (branching, loops, iteration, etc.) • Not mixed with data flow ? • Dynamic control reduces integration and qualification risks 2014 20 6 - System Logical Control (a note) • A combination of IDEF0/N2 (interface connectivity and flow) and FFBD (control flow) can be viewed on an EFFBD diagram • Can get very cluttered (not eye-friendly) 2014 21 7 - System Behavior Typical sequence diagram • So far, we have not examined temporal system behavior • Repeat…IDEF0, FFBD, EFFBD, N2, Schematics do NOT define system timing 2014 22 • Key inspections: • Un-triggered functions • No follow-on trigger • Unallocated functions 7 - System Behavior ? ? ? 2014 23 8 - System Realization, Allocation, and Integrity • Key inspections: • Allocations • Traceability • Continuity • Uneven depth ? Components hierarchy…block diagrams… 2014 24 Top 10 MBSE Tool Inspections SYSTEM INTEGRATION AND QUALIFICATION 2014 25 9 - System “Integrate-ability” ? ? • Key inspections: • Complex functional interactions • Poor external interface definition • Conop-design breakage • Loss of taxonomy control ? ? 2014 26 10 - System “Qualify-ability” • Key inspections: • Poor external interface definition (validation risk) • Conop-design breakage • (ops activities-functionscomponents-etc) • Loss of taxonomy control • Quantifiable requirements • Lack of V&V traceability Design I&Q Requirements CONOP Well-defined Conop + Requirements lead to quality system design resulting in low risk integration and qualification 2014 27 Summary MBSE data-driven, system definition tools can provide keen insights into the quality of system design Document-driven system design and development is not sufficient for complex systems Just building a system model is not enough Employ data-driven tools (not drawing tools) to enable repeatable assessment of system design quality Quick exam of the following can be critical: 1. Requirements 2. Mission and operations and interoperability 3. Functionality 4. Interfaces and continuity 5. System Content Flow 6. System Logical control 7. System Behavior 8. System Realization, Allocation, and Integrity 9. Integrate-ability 10. Qualify-ability 28 2014 References Pix wires: http://www.google.com/urlcsa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=njNH_Jp6GftbT M&tbnid=gfsY3piBTkxO6M:&ved=0CAYQjRw&url=http%3A%2F%2Fmotionleague.com%2F2011%2F04%2Fworkflo w-anddelivery%2F&ei=gJIoU9iRBaiW0QGNx4Fw&bvm=bv.62922401,d.dmQ&psig=AFQjCNE4Kmfdl4QmALgP7B8QCqwAc UHR0A&ust=1395254156966749 Pix screen: http://www.freedigitalphotos.net/ Pix foundations: https://erwin.audi.com/erwin/images/audi/showSystemRequirements/key-639x-300y.jpg Pix structure: http://upload.wikimedia.org/wikipedia/en/8/88/Rubenvent.jpg Pix integrate: http://www.cortjohnson.org/wp-content/uploads/2013/06/Complex-System-Gut.jpg Pix form/function: http://www.studioclues.com/wp-content/uploads/2010/02/form-function.png Pix student: http://www.hsi.com/Portals/22308/images/Frustrated-Instructor--600pxiStock_000014821390XXLarge.jpg All other graphics and content are original to this presentation by the author Some material from CORE models is derived from student projects from Naval Postgraduate School Systems Engineering graduate programs No animals were harmed during the production of this presentation 2014 29