The organization should not rely on just one document to cover the spectrum of this employee's activities.
Just as one person usually plays one role but on occasion may play multiple roles, a given role is usually played by one person but on occasion, such as with shift work, multiple individuals may take turns playing a role. There need be only one job description for the role, not multiple job descriptions for the multiple persons.
WHAT JOB DESCRIPTIONS ARE NOT
To fully understand and appreciate the job description it helps to look at what the job description is not:
1. The job description is not a person specification: A job description is not a person specification or, more commonly called, a job specification. A person specification details the kinds and levels of skills, abilities, knowledge, and so on, that one must possess in order to do the job well or up to a certain organizational standard. Usually, qualifications--experience and educational requirements--are specified in person specifications. These requirements spell out the kinds and amounts of experience and training needed by employees if they are to acquire the skills, knowledge, and abilities necessary to perform at the desired standard.
A person specification describes the kind of person needed to do the job. A job description, on the other hand, describes the nature of the work to be done. In practice, person specifications are often included in the same document with the description of the work. But, it is important to recognize the distinction here and to conceptually separate these two.
2. The job description is not a description of how: A job description is not a procedure or methods description.
Written procedures and methods present the steps to follow in accomplishing something. Procedures and methods show how to execute duties and responsibilities. The job description shows what to do, but not how.
3. The job description is not a performance evaluation instrument: The job description is not a performance level assessment device. It does not specify performance criteria (ways to measure performance) nor does it specify performance standards (desired levels of performance). The job description shows what the worker is supposed to do. How well it is done is determined with a performance evaluation instrument that is best distinguished from, and kept separate from, the job description. Such instruments are used to measure the quantity, quality, timeliness, and cost of one's performance.
Sometimes job descriptions do identify key outcomes--results expected--or accountabilities; but the specification of such is not a substitute for a fully developed performance assessment instrument. However, doing this does aid in developing a performance assessment instrument.
4. The job description is not a set of rules: There is no predetermined set of rules, regulations, policies, or proper practices. These specify acceptable and unacceptable behavior or provide guidelines for doing the work and making decisions relative to the work. For example, good health and safety practices, or management policies on striving for a quality product, should not show up in the job description. At its very basic function, the job description simply identifies what the work is. Rules, regulations, policies, and desired practices should be kept in separate documents.
5. The job description is not a contract: Though a job description is not an employment contract, it has similarities to one. Employment contracts may incorporate job description, or refer to job descriptions, but job descriptions alone are not contracts, and must not be treated as contracts, with all those inherent rigidities. No job description can ever cover all demands that the organization may have to place on the worker. Things inevitably change. Organizations need flexibility in their usage of the human resource.
Outside forces may influence an organization to completely change an employee's job overnight. Treating the job description as a work contract covering a required duration of time is dangerous. It excessively limits the capacity of the organization to adapt.
6. The job description is not a set of objectives or goals: Job objectives and goals are formulated from the job description to assure their relevance and validity. Objectives are targets with measurable levels of accomplishments and time frames for accomplishment. These are specific results to be achieved at some point in time.
7. The job description is not a work schedule: A well-written job description indicates how much time one should spend on different tasks but it does not tell precisely when specific tasks are to be done. The job description may, however, make general implications of when tasks are to be done or give broad time frames for accomplishment. For example, it may point out that certain tasks be done during certain seasons or during a particular part of the year, but it is inappropriate to build into the job descriptions weekly and daily task scheduling. Other documents should be used for this.
The job description shows what the organization's investment in the human resource is for. It is an expression of organizational need. It shows how the human resource should be utilized. It shows how that resource is to contribute to the organization's output. It shows any interested reader what the organization should be getting for what it gives out in paychecks. It is, in a broad sense, something like a contract with the employee, spelling out what demands the organization makes on the employee in exchange for giving the employee rewards such as pay, benefits, and such.
See the following articles for more information: