Write formal specification of a system in Z language notations.Phone Directory SpecificationWe consider a system of phone directory in which a user may have one or more phone number and a phone number might be associated to different people.We assume the following basic types[ PERSON ,PHONE]The state schema is defined formally with the following schemaAnswer the following questions:Is dir a total function, partial function or a relation? Explain why?Write specification of AddEntry operation which takes a person and a phone as input and add it to the directory. This operation doesn’t deal with error cases or provide any output report.Write specification of GetTelphoneNumber operation which takes a person as input and return a report of all telephone number associated with this name.Write specification of GetNames operation which takes a phone as input and returns a list of names associated to this number.Write specification of RemoveEntry operation which takes a person and a phone as input and remove that entry from the directory (if it exists). Phone Directory Specification We consider a system of phone directory in which a user may have one ormore phone number and a phone number might be associated to different people. We assume thefollowing basic types [ PERSON ,PHONE] The state schema is defined formally with the fo… Show more… Show moreComputer ScienceEngineering & TechnologySoftware engineering SOFT ENG 0103320
