entity identification

This content is an extract from GetAhead in Business Analysis - the FULL course is in eBook and multimedia CD-Rom format.

Naming Entities.
Entity names are normally single words and the name chosen should be one familiar to the users. The entity name can include a qualifier in order to clarify their meaning. However, if different names are currently used to describe a given entity in different areas of the organization then a new one should be chosen that is original, unique and meaningful to all of the users. This is explained in the entity identification guidelines below. For example, the terms 'signed contract', 'sale' and 'agreement' might be recreated as the entity 'completed'. Conversely an organization may be using a 'catch all' term to describe what the analyst identifies as being a number of separate entities. For example the term 'invoice' may be being used to describe 3 invoice types - each of which is, in fact, processed in a different manner. In this case prefixing the entity names with qualifiers, like those shown, is likely to be the best solution.

Listing the Potential Entities.
It is common practice for an experienced analyst to adopt an intuitive approach to entity identification, in order to produce a shortlist of potential entities (PE's).
The viability of each of these PE's can then be considered using a set of entity identification guidelines. This should result in some of the PE's being confirmed as entities, whilst others will be rejected. In this exercise you will be asked to identify a set of PE's within a simple business scenario. This should help you to understand and appreciate the entity identification guidelines better. Click on the 'City Cameras Case Study' link in the bookmarks to bring up the camera shop case study. Read this information carefully and see if you can identify the entities. Remember that entities are those things about which data will be stored. Make your own list of those things that you think are likely to be entities, before moving to the next page.

Entity Identification.
You should now have made a list of all of those things mentioned in the case study that could be entities - that is the PE's. Your list should look something like this. There are six PE's shown. From this initial list we will consider the 'Suppliers Price List' to be a likely attribute of the entity 'supplier'. Therefore we shall consider this within the context of the supplier entity. The 'invoicing details' are stated to be attributes of the 'order record' entity, so we shall also discount this as a potential entity at this stage. Remember that entities are described in the singular as they relate to entity types. 'Customer' for example represents the entity type 'customer' which encompasses an infinite number of 'customer' entity occurrences. Taking these four as our list of PE's; each will be discussed in turn.

Is Customer an Entity?
In many business systems, information about the customer is of great importance. An insurance company or bank, for example, could not function without a customer database on which comprehensive personal details are stored. This customer database also serves as an essential resource for selling new financial products and services. But how much customer information is likely to be stored by City Cameras? Are they even going to record the name & address of their customers? Interviews with the owner reveal the answer to be that he has no real interest in storing 'information' about his customers. He only records their details onto any necessary warranty documents and then sends these off to the appropriate supplier. Therefore, in the context of this system customer is not an entity.

Is Product an Entity?
It is a natural assumption that all retail businesses would hold a significant amount of product information. However in this study the only level of product information is that which is held on the suppliers' price lists. Let’s look again at the suppliers price list in the case study. This confirms that product information is held within this system and it is apparent from the case study that products are of real interest. So have we identified an entity? At this stage it would be likely that product would be considered to be an entity. However, you will shortly see why the analysis phase needs to be iterative enabling decisions to be altered later, if necessary.

Is Supplier an Entity?
Once again a natural assumption would be that a retail business would store substantial information about its suppliers. On requesting to see information about City Cameras' suppliers, the owner once again reaches for the suppliers' price lists. Let’s look again at the suppliers' price list in the case study. Each of these lists has the name, address and telephone number of the supplier on the first page. The suppliers' price list is the only place where City Cameras stores information about suppliers. Whilst the early investigation indicated that 'product' was probably an entity, it now becomes apparent that the unique identification of a product and access to the product information is also only possible after locating the relevant suppliers’ price list. It has now been established that all of the information that is stored in relation to the two PE's 'product' and 'supplier' are held in the same place - the suppliers' price list. This means that the suppliers' price list is an entity and that both product and supplier represent information held within this entity. Both supplier and product are therefore identified as being attributes of the entity 'suppliers price list'.

Is Order an Entity?
What about the potential entity 'Order'? Investigation reveals that the re-ordering process consists of visual stocktaking on an ad-hoc basis, followed by mental recall of those suppliers that stock the identified products. The appropriate suppliers’ price lists are then referred to for the up-to-date pricing information and contact details and the order is placed over the telephone. The owner keeps a written record of the orders he places, each order on a separate sheet of paper, and these are then filed. Let's look again at the record of an order, as shown in the case study. This written order record is used to check against incoming products, to verify invoicing details and to chase orders that may be overdue. The 'order' is held as stored information and therefore 'order' does represent an entity.

Final Entity List.
Having started with six PE's (suppliers price list, customer, product, order, invoicing details and supplier), the analysis has identified that only two of these are in fact entities. We eliminated customer, as no customer information is recorded or stored within this retail outlet. The stored information relating to both a product and a supplier was found to only exist within the suppliers' price list. Therefore suppliers' price list was identified as being the only entity amongst these three. Order was confirmed as a system entity and the invoicing details were identified early on as being an attribute of this entity.
Even in this simple scenario it should be apparent that entity identification needs careful consideration. Interestingly, both of the entities that were identified existed as documents within the system. Entities are often synonymous with discrete information stores within a system; whether physical or electronic.

Informal Questioning Approach.
An informal questioning approach can be adopted, in which the analyst asks targeted questions to determine what information is necessary and whether or not that information is recorded within the system. During face to face discussions with users the nouns (or given names of objects) should be recorded; as these often indicate those things that are entities within a system. The existing documentation often contains clues as to the information that needs to be held and once again the nouns in the text may indicate PE's. Every fact that is required to support the business is almost certainly an attribute (or data item). In turn each of these attributes will belong to an entity. If no 'parent' entity can be found for one or more of these low level facts, then this indicates that your entity search is incomplete. However, don't get hung up on the initial analysis. Entity identification can continue once the drawing of the data model diagram has begun. As this diagram is developed and refined further entities may become apparent.

This content is an extract from GetAhead in Business Analysis - the FULL course is in eBook and multimedia CD-Rom format. TOP