What is Engineering?

Engineering: (en-juhneer-ing)

The formal application of scientific and or mathematical principles to achieve a required goal.

This is quite a broad definition, there are many topics that are derived from the ‘pure sciences’ of  biology, chemistry, and physics and the mathematics behind them. Applying these sciences in different proportions gives us the terms we understand as engineering.  There are few ‘pure scientists’. Most professions require a mix with, say biology and chemistry to produce medicine or foodstuffs. Combine biology with physics to develop a space suit.  Physics and chemistry to produce batteries for your phone or car. Engineering is a mix of all these principles to solve problems and produce solutions.

Application of Science

As we, at 3SL, work (Software Engineers – application of logic and mathematical principles) there’s a construction site outside our windows. When you stop and think, there are a large number of principles being used in this civil engineering project. Definitely a lot of physics and mathematics, were used to calculate the safest ways to demolish the old building. A Police station, used to stand on this site. More science will have been used, by structural engineers, to calculate the forces and stresses in the new structure. A hotel and restaurant is to be built. Similarly the ‘Cast-In-Place’ 20m concrete piles that are being drilled into the ground will have chemical reactions occurring in the cement and ballast mix. These have been calculated and tested to produce the right strength pile to support the building.

You may not find much biology being applied on the site (save the organisms now living in the muddy puddles). However,  the chemicals used in the building from water pipes to paints will have had biological studies to ensure they are human safe, or how to use them safely.  Although,  when we have watched the seemingly graceful ballet of the excavators, diggers and trucks we can’t help feeling that the movements and joints were based on mother nature. The human and the control systems they operate, produce movements and operations which make it hard not to anthropomorphise the JCB!

Old Police station/ new Holiday Inn Express site Barrow-in-Furness
Civil Engineering Barrow-In-Furness

Discovery and Development

The principles used in engineering are or have been, observed empirically, calculated mathematically. They are then proven or developed by experimentation or modelling. The results are recorded and can be used in the next application. Therefore, that field of human endeavour moves forward. Whilst each engineering task will have a new goal, the principles that are applied will be based on the underlying sciences. The old building, that was removed, had different foundations from the new one. Development and testing move our engineering forward. We achieve more as knowledge and principles are built upon.


Engineers need to understand the principles they are applying. Whilst these may be at very different levels, they still require planning and thought. No one would expect the building  to be produced by pressing one button on an ‘app’, but neither would you expect the civil engineers and architects to start experimenting with concrete mixes for every building. That’s not to say that there isn’t a group of engineers experimenting with different carbon fibre additives to give the concrete more strength at a reduced weight; their results being fed upwards to the building design engineers of the future.


The formal application of these scientific principles, is how problem solving engineers meet the requirements. We know this as a design process. The whole being a ‘system’, this is systems engineering.  From the initial ideas and requirements management to the finished article, this engineering step is as crucial as the science principles upon which the solution relies. What ever engineering discipline you are in we hope you’ll agree, from concept to creation Cradle is the best tool you’ll see!

The Tail End

Whilst we agree that every job and every individual in our society plays an important role. There has been a bit of dilution of the ‘Engineering’ term in recent years. There’s a tendency for anything that is remotely technical to be labelled engineering. Anyone who understands which end of a screwdriver to hold gets called an engineer. Whilst I agree that there are chemical and physics principles afoot when I place the food in the pan for tea (dinner if you’re not from up North) and when I use the washing up liquid to clean the dishes, I don’t label myself a Domestic Engineer 😉

If you’d like to share your engineering thoughts for possible inclusion in a blog/Tweet/LinkedIn article, let us know your thoughts social-customer@threesl.com

Discussion Comments.

Continue reading “What is Engineering?”

What is a System?


[sis-tuh m]noun:  an assemblage or combination of things, parts, sub systems, members, operations or principles forming a complex or unitary whole.


To answer the question ‘What is a System?’ you first need to understand your context. When you get down to the ‘atomic’ level for your component parts you’re unlikely to model them any further. A local authority may want to model their transport system. This may include vehicles, termini, and ticketing systems. Whilst their model may include the external specifications of a bus (in terms of weight and width) to plan a terminal, they are unlikely to care whether the bus electrical operates on 24v or 48v batteries.  Unless they have to supply charging points at the depots. The tram’s external specification would again include width, height and mass, but it is very likely that the authority would need to know the electrical operation characteristics in their model if they are responsible for the track.

illustration of systems and context
System Components

The bus manufacturer is not really interested in how the local authority terminal looks or operates. However, they may have design constraints for the width or length imposed by their customer. Being able to identify these parameters in their design will help them design any modifications needed to meet the requirements. Some times there is need for shared information. The ticketing system may be supplied by a third party, both the council and the bus vendor will be interested as part of that system will fall within their responsibility. Ticket sales at the terminal, ticket machines fitted on the bus. The bus manufacturer will undoubtedly model their vehicle, there will be detail plans of what connects to what and what operational parameters are needed for each. In this way if a new component is introduced, it is easier to see the impact. The new air conditioning unit needs 48v supply, the bus currently uses 24v how do we assess the impact and know what is dependent on the current voltage line?

Should I model X?

Whether a system, or sub-system is worth modelling heavily depends on your position in the project chain. Deciding whether this is ‘atomic’ level for you is very dependent on your industry. Assessment should be made as to  the likelihood that parameters of the component may affect higher level systems. The likelihood of whether a subsystem is going to be re-used in a number of different high level systems, and whether stakeholder or external constraints need to be considered.

modelled low level components
Circuit model

If you make capacitors, you’ll have specifications for the capacitor, it’s voltage, capacitance, temperature range and so on. However, there is not much you can model at this level. If you also make wire wound inductors, then it will have similar specifications. However, as soon as they are linked together forming an LC oscillator, you have a system. There are two components who’s characteristics interact. If the LC sub-system is being supplied then the voltage at which it is safe to operate will be dictated by the components within. In this case specifying the inductor and capacitor as blocks with characteristics that form the internals of the oscillator will have a benefit in future design or specifying the operation of the sub-assembly supplied to onward customers. As the vehicle parts designer wanting to make a turning indicator unit, whether the oscillator is LC, RC and Transistor or Op-Amp is of little concern as long as the voltage, current and timing are correct. The oscillator would therefore be the atomic level here. The bus designer is not worried about the indicator unit design as long as the brightness and timing meet regulations and the longevity and power consumption are within performance parameters. They would have no interest in modelling the oscillator.

Model Benefits

Query showing relationships
Linked Specification

The fact that your model contains detailed information of the interconnections, parameters and ranges of your atomic components makes querying your model to analyse change much easier. Being able to identify all components that are expecting the same power will aid a designer in assessing the impact or running a different voltage.

Can you model anything?

Pretty much any system can be modelled. Software was maybe the original stable from which many modelling techniques originated, there is a need to define at what point each module interacts with the other modules. The depth to which the functions are modelled will again depend on the context. There would be no point modelling the printer driver in the system beyond the interface, if that driver is purchased along with the printer hardware. Library functions may be modelled in their own right, but the higher level designer will reference them as white or black boxes.

No one model has to contain everything. The passenger movements, purchases modelled as use cases. The hardware components forming the bus. The sub components forming the indicators. The software controlling the ticket system are all separate systems working as a whole.


Digital Certificates in Cradle System Engineering Tool

Starting with the Cradle-7.2 release, we have included digital certificates in the executables in the Cradle system engineering tool distribution for Windows, including the Cradle installer itself.

Digital Certificates

Like a passport or a driver’s licence, digital certificates are issued by a Certificate Authority (CA) to provide proof of identity, in this case for verifying the identity of online entities. However, instead of containing a photograph and the signature of the certificate’s owner, a digital certificate binds the owner’s public key to the owner’s private key.

3SL (our full company name is Structured Software Systems Limited) has obtained a digital certificate from the CA Symantec that we can use to identify any file as being something that we have produced.

Cradle Systems Engineering Tool

3SL’s system engineering tool Cradle contains many executables and other files. These files are supplied as a single distribution file, such as:


It is helpful to us, and to anyone who receives the Cradle software distribution or who looks at any executable that is claimed to be part of the Cradle system engineering tool, to know that:

  • The distribution
  • The files inside the distribution

have come from 3SL and have not been changed in any way after they were created by 3SL.

So, starting with Cradle-7.2, 3SL has digitally signed:

  • The Cradle software distribution
  • The executables inside the distribution

with our digital certificate.


Using a digital signature brings several benefits to anyone who installs or uses Cradle.

Anti-Virus Products

Occasionally, some AV products have incorrectly claimed that a file in Cradle contains a virus. These incorrect reports are called false positives.

Now that Cradle executables are digitally signed, we expect that your AV product will report fewer false positives.


Since the Cradle installer is digitally signed, Windows will display the friendly blue User Account Control (UAC) dialog at the start of the Cradle installation:

cradle system engineering tool digital signatures
Windows Detects 3SL in Cradle System Engineering Tool Installer

instead of the warning yellow UAC dialog.

Executable File Properties

You can verify the digital signature in the Cradle installation files:

Cradle system engineering tool digital certificates
View Digital Certificates in Cradle Executables

If the file does not contain a digital certificate, then you know that the file has been tampered with since 3SL created it, or it was not created by 3SL at all.

Information Assurance

The use of digital certificates is part of 3SL’s commitment to ensuring that Cradle contributes to the information assurance practices in your organisation. You can find more details about other information assurance aspects of Cradle in our white paper here.


We hope that 3SL’s use of digital certificates in the distribution of, and executable files within, the Cradle system engineering tool will be helpful when you next install Cradle and when your AV products next scan a Cradle installation!


Manual ‘ V’ Cradle


When it comes to managing your requirements  and designs there really is no contest between a manual based system and a tool based system.  A cross referenced and baselined design in Cradle is your ultimate goal.


A manual based system at worst is a set of paper requirements, managed in folders with paper-clips and sticky notes. An electronic system may include a number of word processor documents, drawings and spreadsheets. These have very limited, or manually updated meta data to describe how they interlink.

RM tool

A Requirements Management and Systems Engineering software tool brings these elements together in one place and provides the meta data and traceability that binds them together into a successful project.


Paper and pencil versus Cradle
Manual versus Cradle

January 2017 Newsletter

Happy New Year

3SL would like to wish all our customers, partners and suppliers a happy and fruitful 2017.

We hope you are all back to work and busy using Cradle-7.1.2 for your design, requirements management. If you’ve not got the latest version for the start of the year head over to www.threesl.com, login to your account and download it from the Software part of the Resources area in our website here.

If you install Cradle-7.1.2 clients don’t forget to update the server too and visa versa!

Role for RM and SE Tools

We obviously love the fact that Cradle is used on such a diverse set of projects within a huge range of companies. Some customers have fully embraced integrated thinking and manage every aspect of their project with appropriate tools. However, we also know there are pockets of Cradle being used in isolation in engineering departments and disparate projects dotted around our customers’ sites, where unfortunately the wider organisation, their suppliers and customers are just not as tuned into well balanced control and design.

If you find yourself in that situation you may like to use the details in our set of white papers dealing with the uses of information systems in engineering. A paper dealing with the role of RM and SE tool scan be seen here.

Agile Controls

3SL in Australia is distributed by our new partners at Agile Controls.

We are thrilled to announce they have recently signed up their first major customer, we wish them continued success in 2017 and look forward to supporting Cradle’s ‘down under’.

They can be contacted at:

Agile Controls,
108A Tregarthen Road,
+61 427 975 674

Twitter Tips

Sometimes you don’t have time to digest all the information in a newsletter. 3SL often tweet simple usage tips that can make a difference when learning all the capabilities of Cradle.

For example:

Confused about which symbol is which? Hover to see a tool tip or select Draw button from Tools ribbon.
Twitter Tips

tweetClick to view this post or followfollow @threesl if you want to chat about #Cradle or #3SL don’t forget to use an appropriate #tag

Sharing With Others – Web Publisher

When you need a static intranet version of your project, a version you can place on a CD or pen-drive and ship then consider Cradle’s Web Publisher. This allows you to publish your project to a linked set of html pages that can be packaged up and sent to anyone with a browser. You could of course publish parts as a paper report, or as a more complete document with Document Publisher. However, the simplicity of being click a symbol on a diagram and be taken to the specification behind it provides a simple way to share your data with other parties. Of course if you are able to enlighten your customer or supplier, then 3SL will happily demonstrate the full benefits of Cradle and then you can share exports or a common project database.

Sharing Data

Role and Representation of System Requirements in Systems Engineering

We are pleased to announce the third in our new series of white papers that will discuss the role of different types of information in systems engineering processes, and how to deploy each of them in Cradle.

The third white paper in this series discusses system requirements. It is available here:


And as a short link here:


Visit the Resources section of our website: www.threesl.com for this and many other useful resources!

We hope that this white paper is interesting, the next one will appear quite soon!

Rationale for RM and SE Tools

We are pleased to release a new presentation that discusses the need and role for requirements management (RM) and systems engineering (SE) tools and the need for a change in paradigm from document-based processes to data-based processes.

It is available here:


And as a short link here:


Please visit the Resources section of our website: www.threesl.com for this and many other useful resources!

We hope that this presentation is helpful to those considering RM and SE tools!

Role and Representation of User Requirements in Systems Engineering

We are pleased to announce the second in our a new series of white papers that will discuss the role of different types of information in systems engineering processes, and how to deploy each of them in Cradle.

The second white paper in this series discusses user requirements. It is available here:


And as a short link here:


Visit the Resources section of our website: www.threesl.com for this and many other useful resources!

We hope that this white paper is interesting, the next one will appear quite soon!

Role and Representation of Needs in Systems Engineering

We are pleased to announce a new series of white papers that will discuss the role of different types of information in systems engineering processes, and how to deploy each of them in Cradle.

The first white paper in this series discusses needs. It is available here:


And as a short link here:


Visit the Resources section of our website: www.threesl.com for this and many other useful resources!

We hope that this white paper is interesting, the next one will appear quite soon!

UPDATED: April 2020 – Meta data

April Newsletter is Available

We are pleased to announce that our April newsletter 2016 is available here:


which announces the release of Cradle-7.1 that integrates SysML into the systems lifecycle!

If you have an active maintenance agreement with 3SL, you are welcome to upgrade to Cradle-7.1 at any time, but please remember that you will need a new Security Code from 3SL to use Cradle-7.1!