T3: Execution Architecture v2
From SoftwarePractice.org
Contents |
3.1 Process View
3.1.1 Execution Stereotypes
| Icon | Stereotypes |
 | User Initiated |
 | Service |
 | Active |
3.1.2 Execution Architecture Diagram
The execution architecture is an overview of a system's realtime communication between software and hardware elements. The IMS interface uses callbacks to request data from the report storage, where as the reporting system utilises asynchronous calls to manage constantly changing data.
The IMS interface is the only user initiated system where as the diagnostics system and audio visual components are considered active processes as they are constantly operating. The databases and incident and reporting systems are service activities.
3.2 Concurrent Sub-systems View
Audio Visual Subsystem
The AV subsystem is found on site at the intersection and houses the Audio and Video components and when an incident occurs these two components get triggered to record the incident and then relay it to the Incident Analysis component that puts them together and decodes them in a format that can be stored and also viewed by the IMS Interface.
Fig. 1 AV monitoring subsytem
Storage Access Subsystem
The storage access is in place where by when an incident occurs it will store the recording of that incident in an incident database or if an error occurs it will store it in an events database that can be accessed by the user at the IMS Interface.
Fig. 2 Storage access subsystem
Incident Analysis Subsystem
The Incident Subsystem which sits between the AV subsystem and the Storage and IMS interface. It is what does the processing of the incident, basically the brains of the Intersection management system at the Intersection. It processes the audio and video to deduce that an incident has occurred and if so will warn the IMS Interface of an incident and also initiate storage of that incident data.
Fig. 3 Incident Analysis subsystem
Error Diagnostic Subsystem
The Error subsystem is in place to detect any errors that happen on the entire system by using a type of polling methods for each system to send acknowledgment packets and if there is an error it will alert the user through the IMS Interface and also store the type of error and when it occurred on the error database.
Fig. 4 Error Diagnostics subsystem
3.3 Behavior
The IMS System as a whole system works as servers and clients. The IMS system has been split into 3 areas; The on sight component, the Central component and the storage.
The on sight component is the components actually at the Intersection. This includes the Microphone, Camera, Traffic Lights, A/V Processing System. As such these Components can complete their tasks very quickly as there is no distance to cover.
The Central Component includes the Central Monitoring Point as well as the Incident Analysis. These components need to be monitored by the Staff as they are what tells the users when an accident has occurred and other statistics such as total cars passed through the intersection. The information from the Intersection might cause a small amount of lag from the time the incident occurs to the time the message is returned but it is minimal lag.
The Storage Component is also kept close to the Central Component but physically in the same place. As it is just kept for storage it is kept in its own area as to make sure the information is secure. The Information is also sent directly to the storage from the on sight component so the lag in storage is essentially the same as the Central Component.
Keeping the System as a number of servers and clients allows for more servers and clients to be added to the system. As such it means more intersections can be added to the system and just have their own server that also talks to either its own Central Monitoring Point or a shared Monitoring Point.
3.4 Deployment
3.4.1 Physical Components Design
- Remote Input/Output (RIO) Unit(s)
RIO's handle inputs and/or outputs and act as an interface to some field devices by taking digital and/or analogue signals.
- Intersection Management Units (IMU) (s)
Scans the RIO units and field devices in real-time with fibre and/or ethernet cables, analyses and processes the information and sends the data via Distributed Network Protocol (DNP) to the Reporting and User Interface systems. These units will implement the "Intersection Module" (See Implementation Architecture).
- Master Station
This is where the end user (the RTA) can access the system using desktop computers. The system scans the IMU's via DNP and displays the information on a User Interface. From here, users can query IMU's and the Database System.
- Database System
When queried, the Database System can update a Master Station's local database. The Database System stores all reports/records and has a backup server that archives the data.
- Field Device (s)
- Camera(s) - The camera(s) will be responsible for capturing all images.
- Microphone(s) - The microphone(s) will be responsible for capturing all sounds.
- Traffic Light(s) - The traffic light(s) will be responsible for sending information of the current traffic light status to the IMS.
- Sensors - Senses vehicle height and whether or not vehicles pass intersections.
- GPS Switch - Acts as a Simple Time Network Protocol (SNTP) Server to provide accurate and synchronised (to 1ms) time source.
3.4.2 Deployment Models
- The Deployment Model has been designed to accomodate for high scalability, security and also real-time performance.
- Scalability
The system is quite modular, divided into Intersection Management Unit, Master Station and Database System. Any of these modules can be added in the future to allow for more intersections, additional offices and database servers.
- Security
The inputs to the Intersection Management Unit is through circuitry and serial links and thus can be physically protected against sabotage by placing the system in a cubicle with security locks. Firewalls would then ensure the systems integrity over the internet.
- Real-time Performance
A GPS acting as a SNTP server with the additional atomic clocks inside the IMS units will ensure that time stamps are accurate and synchronised.
