Smart-Home as a System-of-Systems reference architecture

This article uses the systems approach to define a reference architecture for the smart-home system domain. It is a continuation of the “Thing-as-a-System reference architecture for #IoT” article ( see https://www.linkedin.com/pulse/thing-as-a-system-reference-architecture-iot-alexander-samarin or http://improving-bpm-systems.blogspot.ch/2016/11/thing-as-system-reference-architecture.html ).

1 Basic concepts

The systems approach is a holistic approach to understanding a system and its discrete parts in the context of their behaviour and their relationships to one another and to their environment.

System domain is a subject field to which the systems approach is applied.

Examples are Smart-Energy, Smart-Home, Smart-Cities and Active Assisted Living (i.e. supporting people of any age with a temporary or permanent disability or impairment). The IoT is considered as a system domain as well.

Functional domain is a set of functions for fulfilment of top-level unit-of-purpose of a particular system.

Networking actors are people, digital services, digital applications and systems interacting over digital networks, primarily, the Internet.

Cyber-Physical System (CPS) is a system (comprises physical and digital discrete parts) that can interact with the physical world and networking actors.

Examples of CPS include autonomous automobile systems, process control systems, robotics systems, automatic pilot avionics, data acquisition and control systems for particle detectors at CERN, etc.

Thing is an intellectual (to some extend) cyber-physical device.

Thing as a System (TaaSy) is accessible, programmable and collaborative via digital services Thing which is considered as an CPS system. See [ref1].

is a person or an organisation served by a particular system domain (e.g. person who lives in a smart-home).

Wikipedia defines the “smart-home” concept or “home-automation” concept (also known as domotics or domotica) as the residential extension of building automation and involves the control and automation of lighting, ventilation, air conditioning, and security, as well as home appliances such as washer/dryers, ovens or refrigerators/freezers that use WiFi for remote monitoring.

Unfortunately, this definition has a few drawbacks, namely:
  • it does not emphasize that all the cyber-physical devices within a particular home must work together as a system to achieve synergy and guarantee a good level of security and other desirable outcomes;
  • home is place where one lives permanently, especially as a member of a family or household (thus final-beneficiaries for homes and buildings are different);
  • other factors must be considered, e.g. political, socio-cultural, legal, etc.;
  • smart-home systems is a class of cyber-physical systems.
Chapter 3 offers another definition of the smart-home concept to overcome these drawbacks.

2 Requirements for any smart-home implementation as a cyber-physical system

Some requirements (as an example) for any smart-home implementation:
  1. Home-related internal activities can be progressively automated by intellectual cyber-physical devices.
  2. Many various intellectual cyber-physical devices can be used synergistically at the same time.
  3. Many various intellectual cyber-physical devices can be used synergistically at the same time and in the same place.
  4. Some final-beneficiary can add new intellectual cyber-physical devices, digital applications and digital services.
  5. Some functions of the intellectual cyber-physical device may be used at the smart-home scale, for example, a stereo could be used to broadcast an alert.
  6. Various aspects of the smart-home functioning (e.g. level of security, environmental impact, comfort, etc.) must be integrally (i.e. including all the available information) monitored, analysed, controlled, alerted and acted on.
  7. High level of trustworthiness (includes security, privacy, safety, reliability, and resilience) of any smart-home implementation.

3 System-forming considerations for any smart-home implementation

Note: The highlighted texts below are the essence of system-forming considerations.

The guiding motif of the smart-home system domain is that all the intellectual cyber-physical devices within a particular smart-home implementation must work together as a system. Explicit systems architecting and engineering is only a way to achieve security and operational excellence of smart-home implementations. In other words, the role of any smart-home implementation is to make a “forest” from individual “trees” (i.e. intellectual cyber-physical devices).

The key architectural decision about the smart-home reference architecture is that two primary concerns, namely, IoT (i.e. intellectual cyber-physical devices ) and smart-home, are separated. Because each intellectual cyber-physical device is, actually, a cyber-physical system then the smart-home is a digital system which includes many Thing-as-a-System (TaaSy) and is aimed for improving functioning of people’s home as a system.

Thus, it is possible to consider Smart-Home as a System of Systems (SHaaSoS). The SHaaSoS primary parts are:
  • final-beneficiaries;
  • other people involved in the smart-home lifecycle;
  • various TaaSy, and
  • various digital services and digital applications.
Technically, the SHaaSoS is a smart composition of various, even non-existing yet, TaaSy. The SHaaSoS as a composition environment must be also very adaptive, flexible and secure, for example:
  • recognise some functionality of TaaSy as essential for the whole system;
  • allow different functional domains to cooperate: for example, healthcare domains may use video surveillance functionality from the security domain;
  • isolate, at the same, various functional domains, subsystems and TaaSy, and
  • integrate everything via explicit and machine-executable processes.

Any SHaaSoS may interact with many external (relatively to a particular smart-home system) networking actors.

Considering that many TaaSy may be added to and removed from the SHaaSoS, the later must be able to control the lifecycles of all its TaaSy. This is something likes configuration management in ITIL.

To reinforce the security, each TaaSy must follow its well-defined contracts that are executed by the SHaaSoS ( see “Digital-contract-as-a-process enables business in the digital world” http://improving-bpm-systems.blogspot.ch/2016/07/digital-contract-as-process-enables.html ). For example, a TaaSy fridge will have several internal & external digital contracts at the same time:
  • with people who live in a particular home;
  • with a producer of this fridge;
  • with a service company for maintenance of this fridge;
  • with some online shops to order various food, and 
  • with the SHaaSoS of a particular home to achieve common goals of energy consumption, to inform about available food, etc.
The fulfilment of some of those digital contracts may require the usage of the Internet. Thus, the TaaSy fridge must be able to “demonstrate” to an in-house Internet router that the TaaSy fridge has rights to exchange data with some external digital services. Any data exchange with other digital services will be prohibited by the in-house router.

Any SHaaSoS itself follows its own digital contracts with people who live in a particular home. Please note, that any SHaaSoS is a bit “more” complex than a major-domo (or castellan, concierge, chamberlain, seneschal, mayor of the palace, maître d'hôtel, head butler and chief steward), because any SHaaSoS has its own contracts with its producer and its supporting services.

In smart home systems it is mandatory to consider the 3D geometry of any smart home because some functions are location-dependent (e.g. the same room); also some TaaSy may be mobile. Another very important factor is the time, because something must occur at a particular time, after some time, etc. The both factors, time and place must be integrated.

Potentially, each the behaviour of each final-beneficiaries must be planned, monitored and anticipated because some functions may operate differently when final-beneficiaries are in groups or individual. Imagine that each final-beneficiary has a trajectory in place x time space and those trajectories may intersect.

4 Mapping between requirements and system-forming considerations

Explicit architecting
Two primary concerns
Composition environment
TaaSy lifecycle
Digital contract
Time and place integration
Progressive automation



Time factor

Place factor

Easy to install



Reuse of functionality


Holistic view



5 Essential views of Reference Architecture (RA)

5.1 Systemic viewpoint

The SHaaSoS systemic groups (or subsystems) are the following:
  • TaaSy bay to connect the SHaaSoS and various TaaSy;
  • Supporting group to provide functionality shared within a digital system (e.g. logging, monitoring, data handling, collaboration, process management, decision management, analytics, etc.);
  • Primary group to provide core business functionality;
  • Coordination group to execute digital contracts between various networking actors, TaaSy and SHaaSoS itself;
  • Managerial group to reconfigure the SHaaSoS, and
  • Operational group to maintain the proper functioning of the SHaaSoS. 

5.2 Functional viewpoint

The smart-home system domain has the following functional domains: security, food & cooking, health, communication, comfort, entertainment, cleaning and maintenance.

Each of those functional domains brings its own TaaSy and usually contributes to some systemic groups.

5.3 Operational patterns viewpoint

Two followings operational patterns are mainly used by the SHaaSoS:

Observe, Orient, Decide, Act (OODA) ( see https://en.wikipedia.org/wiki/OODA_loop ). This pattern is used to detect important events to be reacted with some actions (actually, initiated processes). It is illustrated in the “Event-processing viewpoint”.

Coordination, Event Streams, Analytics, Rules (CESAR). This pattern is used after the OODA pattern because a process (initiated by the OODA) must coordinate some activities, continuously monitor the current situation, make some predictions via analytical tools, and select the best next actions in accordance to existing rules.

5.4 Event-processing viewpoint

A very good presentation of this viewpoint can be found in http://www.slideshare.net/JanThielscher/successful-iot-projects-a-few-lessons that, actually, shows the pattern OODA.

5.5 Application architecture viewpoint

Application architecture of any SHaaSoS follows the platform pattern ( see http://improving-bpm-systems.blogspot.ch/search/label/%23platform ).

Such a platform comprises TaaSy bay and supporting functionality as well as a layer with SHaaSoS-specific functionality.

Solutions which are built on top of this platform are from the following functional domains: operational domain, managerial domain, primary domain and coordination domain. Those solutions use common patterns, tools, services available in the platform. Preferably, those solutions are assembled from microservices ( see http://improving-bpm-systems.blogspot.ch/2016/08/better-application-architecture-apparch.html ).

This architecture is optimised for flexibility (separation of functionality into units-of-deployment), diversity (each SHaaSoS is different), uniformity (to avoid reinventing the wheel) and security (explicit and machine-executable processes).

5.6 Processes (flow of control) viewpoint

Potential processes in the coordination group are the following:
  • Adding a digital contract to the repository of digital contracts
  • Validation of a digital contract
  • Execution (running) of a digital contract
  • Control (including monitoring) of a running digital contract
  • Execution of individual activities within a running digital contract
  • Suspension of a digital contract
  • Resuming of a suspended digital contract
  • Termination (cancellation) of a running digital contract
  • Archiving of a digital contract
  • Removing a digital contract from the repository of digital contracts

5.7 Services viewpoint

All functionality is available as digital services and microservices. All of them have APIs which are developed under the same guidelines (a reference to be provided).

6 Conclusion

To achieve this, data formats and APIs must be flexible enough to be able to add more and more complex TaaSy. Thus, standardization of data formats and APIs must be based on the following practices:
  • system domain ontologies,
  • reusable compact data-structures also known as micro-formats,
  • common modelling guidelines for business entities, 
  • common modelling guidelines for services, and
  • strict versioning. 

7 ANNEX Functions of home (as an example)

The article ( http://oer.nios.ac.in/wiki/index.php/Functions_of_a_Home ) provides a good list of functions of home:
  1. Protective - Home gives us protection from outside heat and cold, sun, wind, rain, etc. It also gives protection to small children and old people who need special care.
  2. Economic - Your home facilitates income generating activities like pickle or papad making or any other similar activity. Families also save money by staying together and sharing everything available. The money thus saved can be more effectively utilized elsewhere.
  3. Religious - A home provides a place for a number of religious activities. You celebrate various festivals while staying in a home.
  4. Educative - A home is the centre of family life. A child’s basic education starts from the home, which helps in the development of personality.
  5. Social - A home facilitates meeting with other people and promotes social interaction.
  6. Affectional - Home is a place where all family members stay together with love and affection.
  7. Status-giving - You enjoy a particular status in the society if you are staying in a home.

A good source of home internal activities to be potentially automated comes from roles of staff who are working for rich people. Normal people would like that, such services will be carried out by appliances or robots or B2B partners.

The best source of internal home activities is - https://www.family-tree.co.uk/news-and-views/royal-household-staff-records-now-online.

A reigning UK monarch typically had 1,000 staff in the royal household. The biggest department was the Lord Chamberlain’s department, which had on average 700 staff and was responsible for the ceremonial and social life of the Court. Traditionally, employees in this department included the ‘above stairs’ servants such as pages, craftsmen, chaplains, physicians, musicians, watermen and Yeomen of the Guard. There is also a number of fabulous occupation titles listed among the royal household staff:
  • Chocolate Maker to the Queen
  • Yeoman of the Mouth to Her Majesty Queen Mary in the Pantry
  • Necessary Woman to the Corridor and Entrance Hall
  • Keeper of the Lions in the Tower
  • Moletaker
  • Master of the Game of Cock Fighting
  • Groom of the Removing Wardrobe
  • Groom of the Stole
  • Strewer of Herbs
  • Laundress of the Body Linen

8 ANNEX Influencing factors (as an example) to be considered by the smart home system domain

Housing preferences change

The “concept of dwelling” is going to be changed as general housing preferences among customers, designers and real estate managers, including lifestyle/activity changes and spatial changes
  • internal spatial organisation
  • space saving
  • flexibility in between

Environmental trends change
  • “Energy-Saving” will increase due to home automation and energy monitoring and controlling. 
  • “Material-Saving” will increase due to the reduction in number of device.
  • “Time-Saving” will increase. 
  • “Transportation-Saving” between home and workspace or other spaces will increase so traffic flows and pollution are going to be controlled.
  • “Land-Saving” will increase and rapid extension of cities will be controlled.
Economic trends change
  • “Space saving with higher quality” is going to be increased as general economic trends

Social trends change
  • “Independently living” especially for elderly (covered by the IEC AAL SyC ) 
  • “Healthy living” – working at home
  • “A man's house is his castle” – being better protected at home
  • Higher preparedness for disasters

Technological trends changes
  • Pervasive computing
  • In-house ICT
  • IoT progress
  • Commoditisation of security equipment (video surveillance, presence detections, etc.).




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karan gupta said...

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