Why MBSE Still Needs Documents

A lot of people are pushing Model-Based Systems Engineering (MBSE) in a way to just deliver models … and by models they mean drawings. The drawings can and should meet the criteria provided by the standards, be it SysML, BPMN, or IDEF. But ultimately as systems engineers we are on the hook to deliver documents. These documents (specifications) form the basis for contracts and thus have significant legal ramifications. If the specifier uses a language that everyone does not understand and only supplies drawing in the model they deliver, confusion will reign supreme. Even worse, if the tool does not enforce the standards and allows users to put anything on the diagram, then all bets are off. You can imagine that the lawyers salivate over this kind of situation.

But it’s even worse really, because not only are diagram standards routinely ignored, but so are other best practices, such as including a unique number on every entity in the database or a description of each entity. As simple as this sounds, most people ignore doing these simple things until later, if ever. This leads us to our first question:  1) Is a model a better method to specify a system?

This question requires us to look at the underlying assumption behind delivering models vs. a document. The underlying assumption is that the model provides a better communication of the complete thoughts behind the design so that the specification is easier to understand and execute. Which leads us to the next question: 2) Can a document provide the same thing?

Not if we use standard office software to produce the document. The way it is commonly done today is that someone writes up a document in a tool like MS Word and then that files is shipped around for everyone to comment on (using track changes naturally) and then all the comments are adjudicated in a “Comment Matrix.” Once that document is completed someone converts it to PDF (a simple “Save as …” in MS Word). In the worst case, someone prints the document and scans it into a PDF. Now we have lost all traceability or even the ability to hyperlink portions of the information to other parts of the design, making requirements traceability very difficult.

However, if you author your document in a tool like Innoslate, you can use its Documents View to create the document as entities in the database. You can link the individual entities using the built-in or user created relationships to trace to other database entities, such as the models in the Action Diagram, or Test Cases. This provides traceability to both a document and the models. In fact, the diagrams in Innoslate can be embedded in the document as well, thus keeping it live, reducing the configuration management problem inherent in the standard approach.

MBSE doesn’t mean the end of documents but using models to analyze data and create more informative documents. Using a tool like Innoslate lets you have the best of both worlds: documents and models in one complete, integrated package.

Professional Development Event Model-Based Systems Engineering

If you are in the Washington, DC Area, April 24-26, 2018, don’t miss the Professional Development Event Model-Based Systems Engineering training course from TSTI.TSTI logo.jpg

This course is intended for practicing systems engineers, payload principle investigators, subsystem engineers or project managers involved in any phase of the space mission life cycle who are curious about application of MBSE to their projects. Some basic understanding of systems engineering principles and processes is assumed.

The course is organized in a unique, modular format allowing you to choose the depth of training appropriate to your interest and time available. Sign up for one, two or all three days.

Want an overview of MBSE? Day 1: Builds a foundation for understanding why MBSE is useful and its overall value proposition for your projects.
Want to be an MBSE user? Day 2: Builds on day one and provides a deeper understanding for potential users of MBSE to explore what types of products and artifacts can be generated and what they can be used for in your projects.
Want to build system models? Day 3: Builds on days 1 and 2 and dives deeper into the details of MBSE languages and tools and challenges participants to build their own models from scratch. While the course uses a specific tool for teaching, the goal of the course is to be “tool agnostic” such that the basic principles can be applied to any tools that a person or project may use.

For details and registration, visit https://www.tsti.net/mbse/ or read the informational brochure. MBSE Virginia Course Flyer

When: Tuesday, April 24 –Thursday, April 26 9 a.m. – 5 p.m.
Where: Marriott Courtyard Dulles Airport, 3935 Centerview Drive, Chantilly, VA 20151
Cost: 3 Days – $1,600, 2 Days – $1,290, 1 Day – $980

It’s Time for Government to Embrace the Cloud Computing Revolution

We are sometimes our own worst enemies! We want something, but at the same time put up barriers to obtain what we want. A perfect example was at an Industry Day I recently attended. The customer had put out a request for information (RFI) and was holding a day to present what was going on with the program to the potential contractors. No procurement was discussed, only information about how they wanted to implement model-based systems engineering (MBSE). In particular they wanted to know what kind of contacting language should be used to provide better requests for proposals (RFP). However, they also said that we could not have one-on-one technical conversations with the government technical personnel. I call that a “self-inflicted denial of service attack.”

Cloud computing is the most common self-inflicted denial of service we encounter. We are all familiar now with DNS (Domain Name System) attacks. They seem to be a frequent occurrence and it’s frustrating when we can’t get on our favorite website because a troll has attacked it.

Because of these trolls and all their attack vectors, many in government have resisted adopting cloud computing. They think: “clouds are dangerous … I don’t have control over my data … someone might steal it.” All the while, their corporate networks have been hacked by every major player in the world. If someone hacks into your corporate network, everything they get is related to your organization and what it does. In other words, everything they get is gold. But isn’t cloud computing, as provided by large providers like Amazon, Google, and Microsoft, more secure than your corporate networks?

Let’s take Google for example. First, they don’t tell anyone the location of their data centers. They provide complete physical security. They build all their own servers from scratch and destroy them when they have finished their useful life. They have all the firewalls and software detection capabilities needed and more. They encrypt the data at rest (and you should be sending encrypted data via HTTP, at least). They randomize the filenames, so you need a map to find anything. The meet and exceed the FedRAMP requirements.

Does your corporate (or government) network do all that? Probably not. An Amazon Web Services’ representative explained to me, “FedRAMP requires over 200 security controls, we have over 2,000 of them.” The last thing anyone from these major “public” cloud providers want is some hacker successfully penetrating their network and capturing critical user data. They could (and would) be sued.

I was talking to a gentleman from the government about cloud computing the other day and he told me, “No one has ever told me how they can clean up a spill on the cloud.” [For those not in the know, a “spill” is when you accidentally put information somewhere it doesn’t belong.] I did not have the presence of mind at the time, but I should have asked “what do you do now with your enterprise e-mail system?” I can guarantee they do not go around tracking down backup and destroying hard drives. Deleting the data results in it being written over hundreds of times in a matter of minutes.

So, it’s time to stop committing denial of service attacks on ourselves. It’s time to embrace the cloud computing revolution and get on-board. The commercial world already did this for the most part half a decade ago. If we want to speed up and improve government, they need to figure out how to use the cloud now.

How to Choose the Right MBSE Tool

Find the Model-Based Systems Engineering Tool for Your Team

A model-based systems engineering tool can provide you with accuracy and efficiency. You need a tool that can help you do your job faster, better, and cheaper. Whether you are using legacy tools like Microsoft Office or are looking for a MBSE tool that better fits your team, here are some features and capabilities you should consider.

Collaboration and Version Control

It’s 2018. The MBSE tool you are looking at should definitely have built in collaboration and version control. You want to be able to communicate quickly and effectively with your team members and customers. Simple features such as a chat system and comment fields are a great start. Workflow and version control are more complex features but very effective. Workflow is a great feature for a program manager. It allows the PM to design a process workflow for the team that sends out reminders and approvals. Version control lets users work together simultaneously on the same document, diagram, etc. If you are working in a team of 2+ people, you need a tool with version control. Otherwise you will waste a lot of time waiting for a team member to finish the document or diagram before you can work on it.

Built in Modeling Languages Such as LML, SysML, BPML, Etc.

Most systems engineers need to be able to create uniformed models. LML encompasses the necessary aspects of both SysML and BPML. If you would like to try a simpler modeling language for complex systems, LML is a great way to do that. A built in modeling language allows you to make your models correct and understandable to all stakeholders.

Executable Models

A MBSE tool needs to be much more than just a drag and drop drawing tool; the models need to be executable. Executable models ensure accurate processes through simulation. Innoslate’s activity diagram and action diagram are both executable through the discrete event and Monte Carlo simulators. With the discrete event simulator, you will not only be able to see your process models execute, but you will able to see the total time, costs, resources used, and slack. The Monte Carlo simulator will show you the standard deviation of your model’s time, cost, and resources.

Easy to Learn

It can take a lot of time and money to learn a new MBSE tool. You want a relatively short learning curve. First, look for a tool that has an easy user interface. A free trial, sandbox, or account to get started with is a major plus. This let’s you get a good feel for how easy the tool is to learn. Look for tools that provide free online training. It’s important that the tool provider is dedicated to educating their users. They should have documentation, webinars, and free or included support.

Communicates Across Stakeholders

Communication in the system/product lifecycle is imperative. Most of us work on very diverse teams. Some of us have backgrounds in electrical engineering or physics or maybe even business. You need to be able to communicate across the entire lifecycle. This means the tool should have classes that meet the needs of many different backgrounds, such as risk, cost, decisions, assets, etc. A tool that systems engineers, program managers, and customers can all understand is ideal. The Lifecycle Modeling Language (LML) is a modeling language designed to meet all the stakeholder needs.

Full Lifecycle Capability

A tool with full lifecycle capability will save you money and time. If you don’t choose a tool with all the features needed for the project’s lifecycle, you will have to purchase several different tools. Each of those tools can cost the same amount as purchasing just one full lifecycle MBSE tool. You will also have to spend money on more training since you will not be able to do large group training. Most tools do not work together, so you will have spend resources on integrating the different tools. This causes the overall project to cost a lot more. This is why Innoslate is a full lifecycle MBSE solution.

 

It’s important to find the tool that is right for your project and your team. These are just helpful guidelines to help you find the right tool for you. You might need to adjust some of these guidelines for your specific project. If you would like to see if Innoslate is the right tool for your project, get started with it today or call us to see if our solution is the good fit for you.

 

Why Do We Need Model-Based Systems Engineering?

MBSE is one of the latest buzzwords to hit the development community.

The main idea was to transform the systems engineering approach from “document-centric” to “model-centric.” Hence, the systems engineer would develop models of the system instead of documents.

But why? What does that buy us? Switching to a model-based approach helps: 1) coordinate system design activities; 2) satisfy stakeholder requirements; and 3) provide a significant return on investment.

Coordinating System Design Activities

The job of a systems engineer is in part to lead the system design and development by working with the various design disciplines to optimize the design in terms of cost, schedule, and performance. The problem with letting each discipline design the system without coordination is shown in the comic.

If each discipline optimized for their area of expertise, then the airplane (in this case) would never get off the ground. The systems engineer works with each discipline and balances the needs in each area.

MBSE can help this coordination by providing a way to capture all the information from the different disciplines and share that information with the designers and other stakeholders. Modern MBSE tools, like Innoslate, provide the means for this sharing, as long as the tool is easy for everyone to use. A good MBSE tool will have an open ontology, such as the Lifecycle Modeling Language (LML); many ways to visualize the information in different interactive diagrams (models); ability to verify the logic and modeling rules are being met; and traceability between all the information from all sources.

Satisfying Stakeholder Requirements

Another part of the systems engineers’ job is to work with the customers and end-users who are paying for the product. They have “operational requirements” that must be satisfied so that they can meet their business needs. Otherwise they will no longer have a business.

We use MBSE tools to help us analyze those requirements and manage them to ensure they are met at the end of the product development. As such, the systems engineer becomes the translator from the electrical engineers to the mechanical engineers to the computer scientists to the operator of the system to the maintainer of the system to the buyer of the system. Each speaks a different language. The idea of using models was a means to provide this communications in a simple, graphical form.

We need to recognize that many of the types of systems engineering diagrams (models) do not communicate to everyone, particularly the stakeholders. That’s why documents contain both words and pictures. They communicate not only the visual but explain the visual image to those who do not understand it. We need an ontology and a few diagrams that seem familiar to almost anyone. So, we need something that can model the system and communicate well with everyone.

Perhaps the most important thing about this combined functional and physical model is it can be tested to ensure that it works. Using discrete event simulation, this model can be executed to create timelines, identify resource usage, and cost. In other words, it allows us to optimize cost, schedule, and performance of the system through the model. Finally, we have something that helps us do our primary job. Now that’s model-based systems engineering!

Provides a Significant Return on Investment

We can understand the idea of how systems engineering provides a return on investment from the graph.

The picture shows what happens when we do not spend enough time and money on systems engineering. The result is often cost overruns, schedule slips, reduced performance, and program cancellations. Something not shown on the graph, since it is NASA-related data for unmanned satellites, is the potential loss of life due to poor systems engineering.

MBSE tools help automate the systems engineering process by providing a mechanism to not only capture the necessary information more completely and traceably, but also verify that the models work. If those tools contain simulators to execute the models and from that execution provide a means to optimize cost, schedule, and performance, then fewer errors will be introduced in the early, requirements development phase. Eliminating those errors will prevent the cost overruns and problems that might not be surfaced by traditional document-centric approaches.

Another cost reduction comes from conducting model-based reviews (MBRs). An MBR uses the information within the tool to show reviewers what they need to ensure that the review evaluation criteria are met. The MBSE tool can provide a roadmap for the review using internal document views and links and provide commenting capabilities so that the reviewers’ questions can be posted. The developers can then use the tool to answer those comments directly. By not having to print copies of the documentation for everyone for the review, and then consolidate the markups into a document for adjudication, we cut out several time-consuming steps, which reduce the labor cost of the review an order of magnitude. This MBR approach can reduce the time to review and respond to the review from weeks to days.

Bottom-line

The purpose for “model-based” systems engineering was to move away from being “document-centric.” MBSE is much more than just a buzzword. It’s an important application that allows us to develop, analyze, and test complex systems. We most importantly need MBSE because it provides a means to coordinate system design activity, satisfies stakeholder requirements and provides a significant return on investment.  The “model-based” technique is only as good the MBSE tool you use, so make sure to choose a good one.

Innoslate Cloud vs. Innoslate Enterprise

This article is meant to help you determine which of these solutions is best for you and your team.

 

Innoslate is offered as a cloud or on premise solution, Innoslate Cloud and Innoslate Enterprise, respectively. It can be difficult to decide which one is right for you. We’ll take you through the pros and cons of each one to help you make this decision.

 

Innoslate Cloud

Innoslate Cloud is flexible and affordable. You can get started quickly, since there’s no download required. It’s easy to share projects with reviewers that are not Innoslate users yet. The pricing plans can be monthly or yearly, so you only have to pay for what you need. Innoslate Cloud is hosted in data centers audited for ISO 27001 and SAS70, so security isn’t a problem.

 

Pros:

Scalability through the cloud

High availability

Flexible pricing plans

Affordable pricing

No download required

 

Cons:

No floating licenses offered

Less administration controls

Less options

 

Innoslate Enterprise

Innoslate Enterprise offers scalability and collaboration beyond the cloud and behind your firewall, with the heightened security of your own server. Innoslate Enterprise is available on unclassified (U/FOUO) and classified (SECRET) level government networks through NSERC.  Innoslate Enterprise is also available on Amazon AWS Marketplace. You can choose between floating and named licensing options. You can get started within seconds on a modern server hardware. The high performance and close proximity of Innoslate Enterprise removes latencies. The server, RedHat Wildfly, implements the latest enterprise JAVA standards with full JAVA EE7 support. Wildfly runs on Windows, Mac, and Linux servers.

 

Pros:

Massive scalability (10 million entities)

Increased administration control

More availability through NSERC and AWS

Floating licensing options available

Fewer latencies

 

Cons:

Less flexibility through pricing

More expensive than Innoslate Cloud

Download required

 

Innoslate Enterprise is perfect if you need your SaaS on your organization’s server or want more administration controls through LDAP. Some organization will have to choose Innoslate Enterprise due to strict security requirements. Check with your IT department to see if you are required to use an on-premise solutions.

 

Still not sure, which solution is right for you? Give us a call at 571.485.7800.

Difference in Floating vs. Named – What’s Right For Me?

Innoslate Enterprise has two licensing type options: Floating and Named. On a daily basis, we hear people ask us “what’s the difference and which one is best for my organization?” They both have different benefits and it’s important to understand what each one is in order to pick the best licensing type for your organization.

Floating Licensing – “a software licensing approach in which a limited number of licenses for a software application are shared among a larger number of users over time.”

 

We like to use the analogy of a family computer vs. a cell phone. Floating licenses are most similar to a family computer. More and more people have individual laptops and iPads, but not too long ago most families had a shared computer. Each family member had their own account. This allowed them a way to login with their own username and password. They could also save their own background, screensaver, files, and other preferences. In other words it would look and feel just like their own computer, but without having to buy each family member their own laptop. However, only one family member can use the computer at a time.

 

One floating licenses is just like that family computer. Multiple people can have a login and use Innoslate as if it were their own license, but only one at a time. This is a really great option if you have a large team and  maybe only a quarter will be using it at a time. For instance, if you have 100 engineers, but only 25 need to use a license at a time. Rather than buying 100 named licenses for each engineer, you could buy 25 floating licenses and save a lot of money.

 

Floating licenses are also a great option if you have a lot of employees joining or leaving a contract frequently. This option allows you to not have to be concerned with whose name is associated with the license. You can easily remove and add employees to a floating license.

 

Named Licensing – “an exclusive licensure of rights assigned to a single named software user. The user will be named in the license agreement.”

 

Back to the family computer vs. cell phone analogy. Named licensing is like a cell phone. Cell phones are not designed for sharing. There aren’t multiple logins. The saved preferences, downloads, and background will not change based on which family member is using the cell phone. They are meant for one person to use it always. Named licensing is exactly the same. Each named license is associated with a name.

 

A named license is cheaper than floating. You can also have free read only users. For example, say you purchased 1 named license. You can then invite as many people as you want to come review your project. They will be able to see the project you shared with them, leave comments, and chat. While if you have a floating license, a read only users consume a license for the duration they use the tool until they sign out.

 

If you know the team that will be using each named license and they will be using it together daily, then named licenses are right for you. It can also be the right option if you have a very large number of reviewers using the software daily.

When making the decision, floating or named, make sure to think about the following:

  • How many concurrent users do we have?
  • Do we have a lot of employee changeover?
  • How many total engineers/requirements managers will use the software daily?
  • How many reviewers will be using the software daily?
  • What is our budget?

Still not sure? Talk to us. We’d be happy to help you decide which option is best for you.

Read next: Innoslate Enterprise vs. Innoslate Cloud – What Is Right For Me?

Why Use an Integrated Solution for Requirements Management and MBSE?

Systems Engineering and Requirements Management

One of the questions we get most is “Why should we get a tool that does both requirements management and MBSE?” With the growth of SaaS products, we are seeing industries all over using an integrated platform. For example, the crm we use, Hubspot, has taken advantage of the unique capabilities of the SaaS market. Hubspot integrated the entire marketing lifecycle into one place from content management, analytics, email automation, etc. We’ve greatly benefited from using only one tool for all of our marketing efforts. Innoslate provides similar benefits with its integrated platform for the entire product lifecycle including the the process modeling, risk analysis, and testing.

A lot of times, we hear people tell us that they “only do the requirements management or the process modeling part of the lifecycle,” therefore they don’t need an integrated platform. Think about what’s your overall goal when you are capturing, managing, and analyzing requirements? You are certainly not just doing this entire process because you enjoy paperwork. You’re goal in requirements management is to meet the goals and needs of stakeholders to complete a product or process. For instance, to create medical devices, large networks, or develop an autonomous vehicle. Let’s keep using the autonomous vehicle example. You’ve done your research, you have 1000s and 1000s of high quality requirements. The document has a complete layout including roadside infrastructure, vehicle safety, DOT regulations, vehicle communication, etc. You know exactly what you are building. The next step is the how you are going to build it.  Whether or not you are the one that does the ‘how,’ at some point in this system or product both parts will have to be completed. Even if the requirements team is handing the project off to another team for analysis and testing, it’s still best to only use one tool. If you don’t, you’ll wind up spending a long time transfering and organizing data. Unfortunately, you’ll probably lose some data in that process, which will result in not having full traceability. With a tool like Innoslate you can develop requirements then create the process of how you will build it.

 

Long story short…There are a lot of reasons you should integrate requirements management with model-based systems engineering.

 

Here’s seven to start with.

 

Saves the entire company time

This is especially true for large organizations. Software tools require training and management. If you have two different tools, you have to do double the training. IT has to spend time managing both tools. It’s even worse if you are putting the software on a server, then IT have to manage two servers. If you want api integration between software, they are probably the ones that have to set that up too. You and your team will lose weeks of time importing and exporting data between tools.  

Saves money

One tool costs much less than two. Innoslate costs much less than most requirements management tools and mbse tools. It’s certainly less than having to buy both. You also don’t have to pay for any additional plugins to make the tools work with each other.

 

Time is money. You are going to save a lot of money by not wasting employee’s time importing all that data into another tool or having IT manage two servers and force integration.

 

Keeps your data all in one place

Besides saving lots of time and stress, keeping your data in one place also reduces risk. You can easily lose data (and not even realize it) during the import/export process. Every tool has a different underlying schema, which can make it extremely challenging to import all the data exactly as the requirements manager intended. This can result in a loss of traceability and make the requirements manager look bad. With using one tool you can easily trace requirements, actions, documents, test processes and more to each other. Innoslate allows you to create relationships from almost anywhere making it simple to create full traceability through the entire project.

 

Collaboration.

Many times requirements managers and engineers struggle to communicate. We just pass our requirements onto the engineers to let them do the next steps. No one wants this to occur. We want both sides to effectively communicate, so they can create a lessons learned. Using two different tools just makes this entire process harder. Innoslate provides version control, chat, comment, and more to make collaborating with diverse teams easy. So next time the engineers want to give the requirements team feedback, they can use the same Innoslate project.

 

Document the Requirements Management Process

What better way to create a requirements management process then to use the advanced built-in models in a MBSE tool? In Innoslate you can model the entire requirements management process. From there you can trace back each action to the requirements or any document. You can also use the collaboration features to make the process a workflow. This way team members will receive email notifications when it’s their turn to do the next step or when something has been approved.

 

Develop requirements from models

If you use a tool that integrates both requirements management and MBSE, you can actually develop low level requirements from the models. The beauty in creating requirements from models is it allows you to analyze the current process and the future process and from that you can understand what you need. This is especially great if you are starting a requirements document from scratch. Innoslate has a built-in feature that automatically creates requirements documents directly from your models. Here’s a great article that shows you how: “Developing Requirements from Models – How and Why?”

 

Gain Valuable Insight

Applying MBSE to requirements management gives you valuable insight you wouldn’t be able to have otherwise. Creating executable models allows you to use the monte carlo simulator, so that you can calculate the variance in cost, time, and resources.Without even leaving the program you can trace back to the requirements document to see if the proposed process meets the specified cost, time, and resources specified in the requirements.

 

Save your organization a whole lot of time, money, and stress by using an integrated solution for a project’s lifecycle. Having the requirements management, modeling, and testing all in one easy to access place will make everyone’s life easier. If you would like to try an integrated requirements management and MBSE solution, sign up for Innoslate at innoslate.com/sign-up.

How to Use Innoslate to Perform Failure Modes and Effects Criticality Analysis

“Failure Mode and Effects Analysis (FMEA) and Failure Modes, Effects and Criticality Analysis (FMECA) are methodologies designed to identify potential failure modes for a product or process, to assess the risk associated with those failure modes, to rank the issues in terms of importance and to identify and carry out corrective actions to address the most serious concerns.”[1]

FMECA is a critical analysis required for ensuring viability of a system during operations and support phase of the lifecycle. A major part of FMECA is understanding the failure process and its impact on the operations of the system. The figure below shows an example of how to model a process to include the potential of failure. Duration attributes, Input/Output, Cost and Resource entities can be added to this model and simulated to begin estimating metrics. You can use this with real data to understand the values of existing systems or derive the needs of the system (thresholds and objectives) by including this kind of analysis in the overall system modeling.

action diagram fmea

Step one is to build this Action Diagram (for details on how to do this please reference the Guide to Model-Based Systems Engineering. Add a loop to periodically enable the decision on whether or not a failure occurs. The time between these decisions can be adjusted by the number of iteration of the loop and the duration of the “F.11 Continue Normal Operations” action.

Adjust the number of iterations by selecting the loop action (“F.1 Continue to operate vehicle?”) and press the </>Script button (see below). A dialog appears asking you to edit the action’s script. You can use the pull-down menu to select Loop Iterations, Custom Script, Probability (Loop), and Resource (Loop). In this case, select “Loop Iterations.” The type in the number (choose 100) as see in the figure below.

Next change the duration of this action and the F.11. Since the loop decision is not a factor in this model, you can give it a nominally small time (1 minute as shown). For the “F.11 Continue Normal Operations” choose 100 hours. When combined with the branch percentage of this path of 90%, means that we have roughly 900 operating hours between failures, which is not unusual for a vehicle in a suburban environment. We could provide a more accurate estimate, including using a distribution for the normal operating hours.

The 90% branch probability comes from the script for the OR action (“F.2 Failure?”). That selection results in the dialog box below.

Now if you assume a failure occurs approximately 10% of the time you can then determine the failure modes are probabilistic in nature, the paths need to be selected based on those probabilities. The second OR action (“F.3 Failure Mode?) shows three possible failure modes. You can add more by selecting F.3 and using the “+Add Branch” button. You can use this to add more branches to represent other failure modes, such as “Driver failure,” “Hit obstacle,” “Guidance System Loss,” etc.

Note to change the default names (Yes, No, Option) to the names of the failure modes, just double click on the name and a dialog will pop-up (as on right). Just type in the name you prefer.

To finish off this model add durations to the various other actions that may result from the individual failures. The collective times represent the impact of the failure on the driver’s time. Since you do not have any data at this time for how long each of these steps would take, just estimate them by using Triangular distributions of time (see sidebar below).

This shows an estimate from a minimum of ½ hour to a maximum of 1 hour, with the mean being ¾ hour. If you do this for the other actions, you can now execute the model to determine the impacts on time.

Note, you could also accumulate costs by adding a related Cost entity to each of the actions. Simply create an overall cost entity (e.g., “Failure Costs” and then decompose it by the various costs of the repairs. Then you can assign the costs to the actions by using a Hierarchical Comparison matrix. Select the parent process action (“F Vehicle Failure Process”) and use the Open menu to select the comparison matrix (at bottom of the menu). Then you will see a sidebar that asks for the “Target Entity,” which is the “Failure Costs” you just created. Then select the “Target Relationship,” which is only one “incurs” between costs and actions, then push the blue “Generate” button to obtain the matrix. Select the intersections of the between the process steps and the costs. This creates the relationships in between the actions and the costs. The result is shown below.

hiearchical comparison matrix

If you have not already added the values of the costs, you can do it from this matrix. Just select one of the cost entities and its attributes show up on the sidebar (see below).

Note how you can add distributions here as well.

Finally, you want to see the results of the model. Execute the model using the discrete event and Monte Carlo Simulators. To access these simulators, just select “Simulate” from the Action Diagram for the main process (“F Vehicle Failure Process). You can see the results of a single discrete event simulation below. Note that the gray boxes mean that those actions were never executed. They represent the rarer failure mode of an engine failure (assume that you change your oil regularly or this would occur much more often).

To see the impact of many executions by using the Monte Carlo simulator. The results of this simulation for 1000 runs is shown below.

As a result, you can see that for about a year in operation, the owner of this vehicle can expect to spend an average of over $1560. However, you could spend as much as over $3750 in a bad year!

For more detailed analysis, you can use the “CSV Reports” to obtain the details of these runs.

[1] From http://www.weibull.com/hotwire/issue46/relbasics46.htm accessed 1/18/2017

Developing Requirements from Models – Why and How

One of the benefits of having an integrated solution for requirements management and model-based systems engineering is you can easily develop requirements from models. This is becoming an increasingly used practice in the systems engineering community. Often times as requirements managers we are given the task of updating or developing an entirely new product or system. A a great place to start in this situation is to create two models a current model and a future (proposed) model. This way you can predict where the problems are in the current systems and develop requirements from there. Innoslate has an easy way to automatically generate requirements documents from models. Below we’ll take a well known example from the aerospace industry, The FireSAT model,  to show you how you can do this.

The diagram below shows the top level of the wildfire detection and alerting system. Fires are detected and then alerts are sent. Each of these steps are then decomposed in more detail. The decomposition can be continued until most aspects of the problem and mechanisms for detection and alerting have been identified. If timing and resources are added, this model can predict where the problems are in the current system. This model can show you that most fires are detected too late to be put out before consuming large areas of forests and surrounding populated areas.

One system proposed to solve this is a dedicated satellite constellation (FireSAT ) that would detect wildfires early and alert crews for putting them out. The same system could also aid in monitoring on-going wildfires and aid in the fire suppression and property damage analysis. Such a system could even provide this service worldwide. The proposed system for the design reference mission is shown below.

The “Perform Normal Ops” is the only one decomposed, as that was the primary area of interest for this mission, which would be a short-term demonstration of the capability. Let’s decompose this step further.

Now we have a decomposition of the fire model, warning system, and response.. The fire model and response were included to provide information about the effectiveness of such a capability. The other step provides the functionality required to perform the primary element of alerting. This element is essentially the communications subsystem of the satellite system (which includes requirements for ground systems as well as space systems).

Innoslate allows you to quickly obtain a requirements document for that subsystem. The document, in the Requirements View looks like the picture below.

This model is just for a quick example, but you can see that it contains several functional requirements. This document, once the model is complete, can then provide the basis for the Communications Subsystem Requirements.

 

If you’d like to see another example of how to do this, watch our Generating Requirements video for the autonomous vehicle example.