Capabilities of the Expert Systems
1. Capturing of the expertise.
2. Codifying the expertise.
3. Duplicating the expertise.
4. Transferring the expertise.
5. Saving the human effort’s time.
6. Saving on the maintenance.
7. Up – dating the knowledge base on the regular basis.

Characteristics of the Expert Systems
1. Should be able to display the intelligent behavior.
2. Should be able to explain the reasoning.
3. Should be able to draw the conclusions from the relationships that are very complex in the nature.
4. Should be able to provide the much needed portable knowledge.
5. Should be able to deal with the certainty.
6. Is not used or tested much due to the reason which says that it is difficult to use.
7. Does not possess the ability to deal with the mixed knowledge.
8. Cannot refine own knowledge base.
9. Are very much difficult to maintain.
10. Limited to the narrow problems.

In today’s world, every company or its management or any individual in same way or the other is dependent on the use of the computer and its various applications. It was the decade of the 1980’s when the coming up of the expert systems was observed by the different users of the world. The experts systems are one of the most enjoy – able applications of the computer and help a great deal in the transformation of the way the corporations developed their software.

The first commercially acclaimed expert system was DEC’s ‘XCON and this was done in the year 1981. It was in the year 1983 when for the first time the expert systems building tools were offered for the sale. But after this year i.e. in the year 1984, the number of the successfully fielded expert systems mushroomed and this mainly occurred because of the high level development tools, which at that time became very much widely available. The years that followed this scenario i.e. in the year 1985 and the year 1986, observed a very large and a very good response from the various types of the users and these were at that time referred to as the hot years but after these years a great dip was observed in the graph of response from the users and these were referred to as the cold years.

But it was the decade of the 1990’s when a huge response was observed and the market of the expert systems developed a lot and during this, the expert systems were largely accepted by almost all type of the users. The expert system technology is mainly based on the research discipline of the artificial intelligence. This artificial intelligence is actually a branch of the computer science and mainly deals with the design and the implementation of the different types of the programs.

Meaning and the Definition Of Expert Systems
From the time of the origin of the expert systems, different types of the persons who use it i.e. the users tend to have an under – standing about the expert system depending on the type of the work in which that particular user is using the expert system. Hence, it can be said that the different users have different definitions of the expert system. There is no particular definition of the expert system which has the ability to completely fulfill or satisfy all the queries of the various users.

According to Peter Jackson, “an expert system can be defined as the computer program that has the ability to represent and reason with the knowledge of some of the particular subject specialist with a view to solving problems or giving any type of the advice.

In general an expert system can be referred to as the technology that has the ability to make the computer programming very easier in the nature and also very effective in the working. The expert system also helps in carrying out the transformation in the computing with the help of the movement of the various programming techniques beyond the numerical programming into a realm of the logical, symbolic programming.

A very better view about the expert systems can be obtained by under – standing the concept of the expert system given by Robert Barwoman and David Glover. According to both of them, expert system can be defined as the “highly specialized computer systems having the ability of stimulating that particular element of the human specialist’s knowledge and reasoning that can be formulated into the knowledge chunks, characterized by a set of the human facts and the different heuristic rules.

According to Bruce Buchanan and Reid Smith, an expert system can be defined as the computer program that –
1. Has the ability to explain both what it knows and the reasons for its answers.
2. Performs well in the problem area.
3. Reasons with the domain – specific knowledge.
4. Uses the domain – specific methods that are heuristic in the nature and are also following the different types of the procedures that are algorithmic.
5. Has the ability to retain the flexibility.

Introduction
Production activity control can be defined as the process which involves the co – ordination of the manufacturing resources – scheduled and controlled. Production activity control includes the various activities related to the scheduling, releasing and the tracking production orders and schedules and then reporting the materials and the resources used and the results of the production process. Production Activity Control involves the various plans associated with the action, reporting the results achieved and reviving the plans etc.

So it can be said that the Production Activity Control is responsible for the conversion of the plans into the actions by providing a much needed proper guidance.

With the help of the Production Activity Control, one can easily meet the timely completion of the various orders by starting the various operations in time as per the plan. Effective Production Activity Control is also responsible for meeting the delivery commitments. Production Activity Control acts as the modules of the MRP/ERP systems, and involves mainly four procedures – releasing, scheduling, monitoring, updating.

According to McMahon, a simple Production Activity Control architecture consists of the following five building blocks –
1. Scheduler
2. Dispatcher
3. Monitor
4. Mover
5. Producer

Functions of the Production Activity Control
1. Helps in the planning.
2. Helps in the execution of the plan.
3. Ensures availability of the resources.
4. Releases the shop orders.
5. Schedules start and completion dates of the jobs.
6. Collects required information for the shop order.
7. Helps in controlling the operations.
8. Establishes order priority.
9. Maintains order priority.
10. Checks actual performance.
11. Monitors and controls WIP, lead times.
12. Reports work center performance.

Role of the Production Activity Control
1. Manages the shop floor production task.
2. Controls the production work flow.
3. Aims achievement of the production plans.
4. Prepares the schedules.

The Production Activity Control cycle
Tasks of the Production Activity Control are cyclic in the nature as the Production Activity Control involves the execution of the work authorized by the release of the documents like the shop order to the shop. Here the planning is compared with the actual production. Production Activity Control helps in the scheduling jobs.

Scheduling and the loading techniques
1. Finite loading –
a. Involves the capacity constraint.
b. Assumes capacity to be finite at any work centre.
c. This type of loading is very realistic in the nature.
d. Planner can know in advance the jobs which can be completed and the jobs which cannot be accommodated.

2. Infinite loading –
a. Assumes the capacity to be finite at any work centre.
b. Capacity constraints are not taken into consideration.
c. Jobs are loaded on the work center without considering the adequacy of the capacity.

3. Forward scheduling –
a. Jobs are scheduled as soon as an order is received.
b. The completion date is evolved by the scheduling of the jobs at the work centers.
c. Due date is ignored while scheduling.
d. Release date is 1st.

4. Backward Scheduling –
a. Jobs are scheduled from end to start.
b. Last operation is scheduled first from the due date.
c. Scheduling continued to be done in the sequence of the operations till all the activities of the jobs are scheduled.
d. Release date is 2nd.

Various types of Operations Scheduling are:
1. Forward operations scheduling –
a. Classified on the basis of the time.
b. All the activities are scheduled from the date of the planned order release.
c. First task of the job is scheduled.
d. Its subsequent task is scheduled on the scheduled completion of the first task.
e. Like this, accordingly all the tasks of the job are scheduled.

2. Backward operations scheduling –
a. Also classified on the basis of the time.
b. Activities are scheduled from the date or the planned receipt date.
c. The last activity is scheduled first.
d. Time of the start of the last task is considered as the time for the start of the previous activity.

Methods used for the operations scheduling
1. Johnson’s two machine algorithm
a. Very effective when the operations sequencing has two machines and the processing time depends on the sequence in which the jobs are loaded.
b. Also used when the company involves a backlog of the orders.
c. Is a very simple process.
d. Also a time saving process.
e. Helps in the determination of the optimal job sequence.

2. Index method
a. Used for the purpose of the loading and also for allocating the different jobs to the different machines.
b. Generally orders are assigned on the basis of the “first come first assigned” method.
c. But does not provide optimum loading.

3. Critical path analysis
a. Helps in the determination of the scheduling of the activities of the projects.
b. Reveals inter – relationships between the different activities of the project.
c. Reflects the uncertainty in the durations estimated for the various activities.

4. Critical ratio scheduling
a. Helps in the establishment and the maintenance of the priorities among the jobs in a factory.
b. Concept of “critical ratios” is used widely.
c. Helps in the expedition of the functions of the PPC.

1. Performance standards –
a. First and the foremost need of the operations scheduling.
b. Helps the scheduler to find out the machine capacity in order to assign the required machine hours and the man – hours for the various activities.
c. The performance standards play a very important role in the good operations scheduling and this is always possible if the time study or the industrial engineering department exists in the plant.
d. The performance standards for such repetitive jobs are available.
e. And for the new jobs, they can be determined from the tables of the synthetic standards prepared by the department.

2. Unit of the measurement –
a. Means the unit in which the loading and also the scheduling is to be extended.
b. The most commonly used units of measurement in the engineering companies are the man – hours or the machine – hours.

3. Unit of the loading and the scheduling –
a. Means the duration for which the loading and the scheduling should be done.
b. The unit of the loading and the scheduling – scheduled start and the finishing timings – are mainly dependent on the scheduling needs of the company.
c. Scheduling should be done on the daily basis if the company makes promises in days.

4. Effective capacity per work centre –
a. Means the effective hours that can be used for the production on the machine or on the work centre in a week or in a month.
b. Theoretical capacity is equal to the number of the normal working hours of that machine.
c. Some interruptions may occur during the process and some of these interruptions can be summarized as follows –
i. Power failure.
ii. Rework.
iii. Waiting for transport.
iv. Preventive maintenance.
v. Waiting for the inspection.
vi. Tool try – out, jigs and the fixture try – outs.
vii. Operatives’ trade test.
viii. Operators involved in some other activities like the functions, celebrations etc. – leaving the production operations aside.
ix. Machine used for the technical studies.
x. Operator left the work place for the official decision.
xi. Machine breakdown – may be technical or mechanical in the nature.
xii. Operator absence.
xiii. Breakage in the tool.
xiv. Operator training time.
xv. Starting late.
xvi. Early close.
xvii. Over – time.
xviii. Incentive payment collection.

5. Extent of the rush orders –
a. When considering the scheduling process, the rush – orders play a very conclusive role.
b. Never a machine should be subjected to 100 % effective capacity, simply because of the reason that if any rush order comes in, and then the scheduling has to be changed.
c. The various methods used in the accommodation of the rush orders can be summarized as follows –
i. Leaving some capacity unscheduled on each machine per period.
ii. Leaving some in scheduled capacity between the two scheduled jobs.

6. Overlapping of the operations –
a. Means running of a job simultaneously on more than one machine.
b. Occurs in the jobs which involve two or more operations.
c. Reduces the manufacturing cycle time.
d. Reduces the delivery period to the customer.

7. Loading charts
a. These charts specify the work that is to be carried out in each section or the department of the company during the period under the review.
b. Helps in knowing the accumulated load at a given time for a given machine.
c. Helps in the identification of the periods that are available for the allocation in the future to orders needing this machine.