Marcia$$s Dry Cleaning Marcia Wilson has been successfully using the MDC database described in Chapter $7.$ Her business has grown so much, however, that she wants to explore the possibility of using RFM analysis on her customer base and the possibility of a document database for some of her data in the future. She also wants to investigate how her database might work in the cloud.

Describe how an RFM analysis could be useful in Marcia$$s business.

Marcia has heard good things about XML as a way of structuring data; in addition, she may want to be able to easily share data with other local businesses using a standardized XML format. As an experiment, she would like to create XML data to model her customer data. Create an XML Schema file to model her customer data and create a matching XML document file containing data for at least three of her customers.

Marcia has also heard wonderful things about JSON$-$based document databases and would like to experiment with such a system with the possibility of deploying it in the future. Create a JSON$-$based document database in ArangoDB for Marcia containing three collections: one for customers, one for services, and one for invoices $($with the invoice items stored within each invoice$).$

Based on the database you created in the previous question, write the following queries in AQL:

Retrieve the descriptions of all services costing over $$5.$

For each invoice totaling over $$100,$ retrieve the invoice number, date in$,$ and service ID and quantity of all items in the invoice.

Group the invoices by customer and return, for each customer, the customer number and the total amount spent by that customer on all their invoices combined.