Advanced Software Engineering course - Guest Lecture ME4AWSN - a Modeling Environment for Architecting WSNs Here you can find the research paper presenting the concepts described in this lecture: http://goo.gl/XBB4k This presentation has been developed in the context of the Advanced Software Engineering course at the DISIM Department of the University of L’Aquila (Italy). http://www.di.univaq.it/malavolta

1. Università degli Studi dell’Aquila
ME4AWSN
Ivano Malavolta
DISIM Department, University of L’Aquila
ivano.malavolta@univaq.it

2. The material in these slides may be freely reproduced
and distributed, partially or totally, as far as an explicit
reference or acknowledge to the material author is
preserved.
Ivano Malavolta

3. Problem Definition
ME4AWSN
Software Architecture
Nodes Configuration
Physical Environment
Keeping Models Integrated
Example

4. What is a Modeling Environment?
A software application that provides comprehensive
facilities for developing models
• model creation, deletion
• model editing (graphical, textual, ...)
• syntax rules enforcing ... what about
modeling frameworks?
• ...

5. From the SESENA 2012CfP: Abstraction
“the development of WSN software is still carried out in a rather
primitive fashion, by building software directly atop the OS and by
relying on an individuals hard-earned programming skills”
“WSN developers must face not only the functional application
requirements but also a number of challenging, non-functional
requirements and constraints resulting from scarce resources”
Separation of Model-based
concerns Analysis

6. Abstraction
by masking the complexity of low-level, hardware details
Separation of
concerns
by clearly separating SW, HW, and deployment aspects of
a WSN
Model-based
Analysis
by facilitating the analysis of both functional and non-
functional properties

7. in this lecture we focus on this part
Separation of Model-Based
Abstraction
concerns Analysis

9. Problem Definition
ME4AWSN
Software Architecture
Nodes Configuration
Physical Environment
Keeping Models Integrated
Example

10. It is composed of 3 modeling languages
Physical
Details about environment
WSN nodes
Software
Architecture

11. Structure
components
ports
application data
messages
Behaviour
events
conditions
actions

12. Component. A unit of computation with internal state and well
defined interface. Each component can contain a behaviour
specification and a set of application data.
MessagePort. Specifies the interaction point between a
component and its external environment.
Incoming messages arrive at InMessagePorts
Outgoing messages are sent via OutMessagePorts
Connection. It is a unidirectional communication channel
between two message ports.

13. Application Data. Local variables declared in the scope of the
component. It is manipulated by actions defined in the
behaviour of the component.
There are two types of application data:
• Primitive
• integer, string, real, boolean
• Structured
• Enumeration
• Structure

14. Operations on Application Data:
• arithmetic
• + - / * Assignment is done via
• boolean a dedicated Action in
• AND, OR, NOT the behaviour
• relational
• > >= < <= !=
Application data reference
Structure Member reference

15. Each Component can contain a description of its behaviour
The behaviour is based on:
1. Events-conditions-actions
2. Modes

16. Each Component can perform actions:
Sense gets some data from a sensor and stores the read
value into a specific application data
ex: get current temperature
Actuate activates and actuator, optionally an application
data can be used to pass a parameter to the actuator
ex: actuate a water sprinkler

17. SendMessage sends a message via a specific message port
Optionally, the payload of the message can be specified by
passing an application data as parameter
Types of available messages:
Unicast to a single receiver
Multicast to a set of receivers
Broadcast to every node containing the target
component

18. StartTimer starts a timer which can be triggered later
cyclic: true if the timer must be periodic
delay: the time (in millisecs) that must pass before the first activation
period: the period of the timer (in millisecs), if it is a cyclic one
StopTimer stops a previously started timer
StoreData puts some (manipulated) data into an
application data of the component

19. SyncServiceCall calls an external service (ex. web service)
data: optional, it is the parameters that can be passed to the service
dataRecipient: the application data which will be filled with the result
AsyncServiceCall calls an external service, the result of the
call will be available via a dedicated event
data: optional, it is the parameters that can be passed to the service
Fork and Join are used to sync the control flow

20. Each component can react to specific kinds of events:
ServiceCallback is triggered when the result of an
AsyncServiceCall is available
dataRecipient: the application data which will be filled with the result
ReceiveMessage is triggered when the component
receives a message
dataRecipient: the application data which will contain the payload
fromMessagePort: the port that received the message
TimerFired is triggered when a previously started timer is
activated

21. Behavioural flow is specified by means of Links
A link can exist:
1. from an event E to an action A: in this case after the event E is
triggered, A will be executed
2. from an action A1 to another action A2: in this case, A2 is
executed immediately after A1
Conditions are boolean expressions (optionally) associated to links
The execution flow goes through a link only if its condition
evaluates to true

22. A mode is a specific status of the component
ex. sleeping mode, energy saving mode, etc.
Initial Mode is the first mode which is active when the component
starts up
At any given time, one and only one mode can be active in a
component
The component reacts only to those events which are defined
within its currently active mode

23. A component can switch from a mode to another by means of
mode transitions
Mode transitions link together modes by passing...
from a special kind of action called ExitMode
to a special kind of event called EnterMode
in this way actions and events can be linked to modes entry and exit points,
creating a continuous flow among modes

24. Problem Definition
ME4AWSN
Software Architecture
Nodes Configuration
Physical Environment
Keeping Models Integrated
Example

25. Types of nodes
OS
MAC protocol
routing protocol
installed sensors
installed actuators
energy sources
communication devices

26. A nodes specification is composed of a set of WSN node types
Node Attributes:
• OS
• ex. TinyOS, Contiki, Mantis, LiteOS, ...
• macProtocol
• ex. T-MAC, S-MAC, WiseMAC, SIFT, ...
• routingProtocol
• ex. GEAR, LEACH, HEED, ...

27. Node
Sensors
Sensors
Microcontroller Sensors
Memory
RF Memory
ADC Memory
CPU Actuators
CPU
CPU Actuators
DAC Actuators
Timer
RF
Memory Program memory RF
RF
Energy Source
Energy Source
Energy Sources

28. The following elements can be attached to a WSN node:
• energy sources (one or more)
• continuous
• degradable (initialStoredEnergy in Joule)
• harvested (initialStoredEnergy in Joule, harvestingEnergyRate in Joule)
• sensors (zero or more)
energyConsumptionPerSample (mJ), idleEnergyConsumption (mJ)
ex. light sensor, temperature sensor, radio sensor, ...
• actuators (zero or more)
energyConsumptionPerSample (mJ), idleEnergyConsumption (mJ)
ex. water sprinkler, leds, lights, heating system switch, ...

29. A node can contain the following elements:
• RF Communication Device (zero or more)
represents the radio device to communicate with other nodes
Attributes:
float transmissionPower in dBm
float receiveSensitivity in dBm
float[1] frequency in MHz
float antennaGain in dBd
String modulation // name of the modulation method
String encryption // name of the enc. algorithm

30. A node can contain the following elements:
• Memories (one or more)
represents external storage memories of the node
Attributes:
float averageReadingEnergyConsumption in mW
float averageWritingEnergyConsumption in mW
int[1] size in Kb

31. Microcontroller (one)
represents the entity which performs tasks, processes data
and controls the functionality of other components in the
sensor node
Microcontroller 0_1
1_*
0_* ADC RF
CPU
CPU
0_* DAC CPU
Timer 1_*
Memory Program memory
1_1 1_1

32. • ADC (zero or more)
Attributes:
int resolution // # discrete values it can produce
int bits // 8 bits, 16 bits
int channels // #channels
• DAC (zero or more)
Attributes:
int resolution // # discrete values it can produce
int bits // 8 bits, 16 bits

33. • Processor (one or more)
Attributes:
int[1] frequency in MHz
float[1] cpi // cycles per instruction
• Timer (one or more)
Attributes:
int bits // 8 bits, 16 bits
• RF Communication Device (0_1) – internal radio transceiver
• Memory (one) – same role as RAM memory in PCs
• Program Memory (one) – stores the program running on the node

34. A Node can specify a set of Power Modes
Each power mode identifies a set of node elements (such as
memory, DAC, RF comm. device, etc.) and distinguishes between
which elements are active and which elements are disabled
Mode A Mode B

35. Problem Definition
ME4AWSN
Software Architecture
Nodes Configuration
Physical Environment
Keeping Models Integrated
Example

36. A 2D space with obstacles
freely positioned
with their own shape
with attenuation coefficients

37. The Environment represents the overall area in the 2D space in
which the WSN will be deployed
Attributes:
string name // the name of the area
float [1] width // the width of the bounding box of the area
float [1] height // the height of the bounding box of the area
imagePath // the image used as background in the editor
The environment contains a set of Obstacles

38. An Obstacle specifies any kind of relevant element which can be
placed in the environment
Attributes:
string material // the name of the material of the obstacle
(ex. concrete wall, wooden door, glass, ...)
float [1] attenuation // the “thickness” of the obstacle
// it ranges from 0 to 1
Coordinate [2_*] shell // the perimeter of the obstacle in the
2D space

39. Problem Definition
ME4AWSN
Software Architecture
Nodes Configuration
Physical Environment
Keeping Models Integrated
Example

40. Two special models that link together SA, nodes and
environment specifications

41. Weaves together an SAML model and a NODEML model
It defines how components are deployed into each configured nodes
Types of link:
• Mapping maps a component to its corresponding node configuration
• Sensor Mapping maps a Sense action in a component to a Sensor in
a node
• Actuator Mapping similar to the Sensor Mapping, but for actuators
• Communication Device Mapping maps a Message Port in a
component to an RFCommunicationDevice in a node
• Mode Mapping maps a Mode in a component to a Power Mode in a
node

42. MAPML models semantically represent the classical notion of
deployment of software components onto HW nodes
Separation of Concerns
It helps in clearly separating the application layer of a WSN from
all the other lower levels
this aspect is new in the WSN domain
Architects can focus on the application from a functional point of view in
SAML, and only later they will focus on low-level aspects

43. Weaves together a NODEML model and an ENVML model
It defines how node configuration are
1. instantiated, and
2. virtually deployed in the physical environment
A DEPML model presents a single type of link: Deployment Link
A deployment link considers a node configuration in the NODEML
model, and assigns it to an area within the physical environment

44. An area is a portion of physical environment (i.e., the environment
element defined in the ENVML model)
Each node type can be instantiated ”n” times within a specific area
this allow architects to focus on generic components and
node types in SAML and NODEML, while in DEPML we consider the
final shape of the network
An area has two properties:
1. Shape: the perimeter of the area defined as a set of coordinates
2. NodesDistribution: how the “n”nodes are positioned in the area

45. Nodes can be distributed in three different ways:
Random Grid Custom
each node is placed nodes are placed on a each node can be manually
grid with a certain
randomly within the area placed within the area
number of rows and
columns
N2
N1
N1
BS
N3

46. In custom distribution, each node can be N2
N1
individually specified in the area by: N1
BS
1. its name N3
2. the coordinates of its position
A nodes name pattern cane be given to an area independently from
the distribution type
they are used to have a way to refer to the names used as targets of Send
Message actions in SAML models
Available patterns:
name<number>, name<Letter>, name

47. Graphical and Tree-based editor for SAML
models
graphical
editor palette
bird
view
properties

48. NODEML: Graphical and Tree-based editor
DEPML: Graphical editor with background image
MAPML: Tree-based editor
DEPML: Tree-based editor

49. languages programming
refinement framework definition
modeling code
generators model-based
editors analysis tools

51. The fire alarm system considered is composed of two types of sensors that
are temperature and smoke sensors. There are also sprinkler actuators that
are used to enable the water flow in case of fire.
Temperature sensors monitor the temperature at regular intervals (every 30
seconds). When a temperature sensor reads a value that exceeds a specified
threshold, it sends an alert message to the base station.
Each smoke sensor receives the alert and checks for smoke. When a smoke
sensor detects smoke it sends an alarm message to the sprinklers to activate
the water flow.
The automatic heating system is composed of the same temperature sensors
of the fire alarm system, a base station and various heaters.
Temperature sensors send readings every 30 seconds to a base station. This
is placed at the centre forming a star topology.
The base station averages the readings and decides whether or not the
central heating system should be on.