Advanced Business Systems (ABS) is a consulting and staffing company providing specialized staffing and consulting services to clients in a variety of different industries. It has offices in major U.S. metro areas and has ongoing relationships with Fortune 500 companies. Its areas of services range from software development and network engineering to geo-information systems. It has more than 50 regional offices in the U.S. and five offices in Canada. It plans to expand to other countries in the future. When an ABS client company determines that it will need a contractor or temporary professional, it issues a staffing request against the contract it had previously negotiated with ABS. The contract manager in ABS reviews the staff request and ensures that the request is valid with its current contract with its client from the database. If the request is not valid, the contract manager sends the staffing request back to the client and explains the reasons and asks for the need for starting a new contract. If the request is valid, the contract manager will start recruiting requests by putting the request into its staffing database. The staffing request is then sent to the ABS placement department. In the placement department, the placement specialists will check the job requirements and candidate's qualifications. If there is a qualified candidate, the specialist will notify the candidate and put a note in the database. If a qualified candidate cannot be found or not immediately available, the specialist notifies contract managers and the recruiting department; the recruiting department starts search outside immediately. The recruiting department normally has thirty days to find an outside candidate and send the qualified candidates to the placement department to review. If an internal qualified candidate is confirmed with his or her availability, the confirmation will be sent to the arrangement department. In the arrangement department, the candidate works with the specialists to further confirm the placement details, such as starting date, location, compensation (such as, per diem), and travel arrangement. The final confirmation will be sent to the client along with a billing schedule. If the client agrees with the arrangement, he/she acknowledges the arrangement with contract managers in the contract department. The contract manager then puts a memo into its database and closes the request. Note: You may create and/or assume all necessary assumptions needed for the completion of this assignment. Instructions Write a 3–4 page paper in which you: Create a package diagram of the problem domain layer using the communication diagrams and the CRUDE matrix through the use of graphical tools in Microsoft Word or Visio, or an open-source alternative such as Dia. Note: The graphically depicted solution is not included in the required page length. Perform and explain the verification and validation walk-through of the package diagram. Create a set of invariants for attributes and relationships and add them to the CRC cards for each class in the structural model using Object Constraint Language (OCL). List the classes in the structure model. Choose one class and create a contract for each method in that class. Note: Be sure to use OCL to specify the preconditions and the post conditions. Create a method specification for each method using both structured English and activity diagram for the algorithm specification through the use of graphical tools in Microsoft Word or Visio, or an open-source alternative such as Dia. Note: The graphically depicted solution is not included in the required page length. Use at least two quality resources in this assignment. Note: Wikipedia and similar websites do not qualify as quality resources. Your assignment must follow these formatting requirements: This course requires the use of Strayer Writing Standards **SEE ATTACHED**. For assistance and information, please refer to the Strayer Writing Standards link in the left-hand menu of your course. Check with your professor for any additional instructions. Include charts or diagrams created in Visio or Dia. The completed diagrams/charts must be imported into the Word document before the paper is submitted. The specific course learning outcome associated with this assignment is: Determine the steps and principles of design modeling with UML.