Measuring the Requirements Allocation Capacity within a System of Systems

David FlaniganThe Johns Hopkins University Applied Physics Laboratory

Dr Peggy BrouseGeorge Mason University

April 22, 2023

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Outline

Objective Literature Review Steps in the SoS Requirements Allocation

Process Case Study Next Steps

Objective

During initial development of a System of Systems (SoS), many SoS do not have authority over the systems and need to work with developers and stakeholders to identify and allocate requirements to the system level

Traditional Systems Engineering techniques do not have the ability to allocate SoS requirements and determine if this they are satisfactory or not

A process and series of metrics are offered to develop SoS requirements allocation

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Literature Review We examine existing requirements allocation processes for

any methods / metrics applicabile to SoS: Multi-attribute optimization process (Sutton) Decomposition of top-level requirements (Kusiak and Qin) Martin et al. studies three Requirements Engineering (RE)

process models: • Linear incremental model (Kotonya & Sommerville)• Purely linear model (Macaulay)• Iterative and cyclical model (Loucopoulos and Karakostas)

Interaction matrix to identify system – system interactions (Fry and DeLaurenitis)

We are motivated to develop a SoS requirements allocation method since there is currently no process to ensure this SoS allocation is

successfully conducted

SoS Requirements Allocation Process

• Define the SoS problem space and scope• Inventory existing system objectives and

requirements• Allocate SoS requirements to system

requirements• Assess the SoS requirements allocation

Case Study An illustrative case study involving a US Navy Carrier Strike

Group (CSG) will conduct Surface Warfare (SUW), e.g. identifying and engaging hostile surface platforms

Enterprise Command and Control Requirements and Common Architecture on US Navy Surface Combatants, Naval Postgraduate School, NPS-SE-09-003, June 2009.

Step 1: Define the SoS problem space and scope

Limited to a US Carrier Strike Group – with only the organic platforms and not external systems (e.g. satellites, joint forces, other systems)

Our SoS scope

Enterprise Command and Control Requirements and Common Architecture on US Navy Surface Combatants, Naval Postgraduate School, NPS-SE-09-003, June 2009.

Step 2: Inventory existing system objectives and requirements

For our example, we look at three specific systems and their missions from various sources

O'Rourke, R. "Unmanned Vehicles for US Naval Forces: Background and Issues for Congress". DTIC Document , 2005.

US Navy. 2011. "Destroyers - DDG." Last modified 31 January 2011. http://www.navy.mil/navydata/fact_display.asp?cid=4200&tid=900&ct=4.

US Navy. 2009. "F/A-18 Hornet strike fighter." Last modified 26 May 2009. http://www.navy.mil/navydata/fact_display.asp?cid=1100&tid=1200&ct=1.

Platform Missions

F/A-18E/F Super Hornet

Air superiority, fighter escort, reconnaissance, aerial refueling, close air support, air defense suppression and day/night precision strike

Guided missile destroyersAnti-Air Warfare (AAW), Anti-Submarine Warfare (ASW), and Anti-Surface Warfare (ASUW)

Naval Unmanned Aerial Vehicle (UAV) Intelligence, Surveillance, and Reconnaissance (ISR)

Step 3: Allocate SoS requirements to system requirements

Step 3a: Decompose SoS objective to SoS phases Step 3b: Identify frequency of use of each SoS phase Step 3c: Catalog the system-system interfaces within

each SoS phase

Step 3a: Decompose SoS objective to SoS phases

For our example, we focus on one SoS mission• Surface Warfare (SuW) mission: the detection, tracking,

and engagement of hostile surface platforms We use the SuW kill chain to functionally describe

the mission in six distinct phases: find, fix, track, target, engage, and assess

We leverage an example from NPS that describes a generic SuW kill chain and develop an activity diagram to map to our specific systems

Step 3a: Decompose SoS objective to SoS phases

Enterprise Command and Control Requirements and Common Architecture on US Navy Surface Combatants, Naval Postgraduate School, NPS-SE-09-003, June 2009.

For this example, we derive the given SUW kill chain and convert into a SoS activity diagram that contains SoS phases and intra/inter-phase interfaces

Step 3b: Identify frequency of use of each SoS phase

For this example, we can solve the frequency based on simple assumptions and a 4-hour air wing event time constraint; future work would develop a full-

scale discrete event simulation to calculate percentages

Step 3c: Catalog the system-system interfaces within each SoS phase

Identify the system-system interactions within each SoS phase transition• Extending Fry and

DeLaurentis’ research on adjacency matrices to define SoS interactions

• We must look at each SoS phase since there may be different systems interacting and differing levels of effort

Find/Fix to Track/Target

C2 Aircraft Surface Ship UAVC2 0 0 0 0

Aircraft 1 0 0 0Surface Ship 0 0 0 0

UAV 1 0 0 0Track/Target

to EngageC2 Aircraft Surface Ship UAV

C2 0 1 1 0Aircraft 0 0 1 0

Surface Ship 0 0 0 0UAV 0 0 0 0

Engage to Assess

C2 Aircraft Surface Ship UAVC2 0 0 0 0

Aircraft 1 0 0 0Surface Ship 0 1 0 1

UAV 1 0 0 0

Fry, D. N., and D. A. DeLaurentis. "Measuring Net-Centricity". Paper presented at System of Systems Engineering (SoSE), 2011 6th International Conference on. IEEE, 27-30 June. 264-269.

Step 4: Assess the SoS requirements allocation

Total Network Capacity Requirements• Using our series of adjacency matrices, calculate

the amount of network capacity that each system would require for the SoS mission

System contribution throughout the SoS• Since we know the frequency of each SoS phase

and the number of activities that are used within each phase, we can calculate the contribution of each system within the entire SoS mission

The airborne platforms have the greatest network usage and contribute most to the SoS mission, which helps to identify & allocate system-level requirements

PlatformNetwork usage

C2 11%Aircraft 40%Surface

Ship 14%UAV 35%

PlatformSystem

contributionC2 9%

Aircraft 44%

Surface Ship 5%UAV 42%

Our calculations are intuitive: for a mission that heavily relies on the find/fix phase to search out a target (this often happens in SuW missions to detect and identify a

single ship in a large body of water)

Next Steps Add multiple missions for the SoS to simultaneously

execute• Identify where adding more missions would compete and

adversely affect other missions• Where does the over-allocation of particular systems

occur? Quantify the reallocation process of system

contributions to SoS requirements• What happens to different SoS configurations? (e.g. have a

more ship-centric activity flow)

Questions