Logic Modeling Logic and timing are not represented on data flow diagrams or entity relationship diagrams Processes contain logic what happens under what conditions Logic is modeled per process Types of logic sequence conditions iteration Structured English Uses a subset of English Uses indentation similar to programming Uses process type verbs like READ WRITE GENERATE CHECK PRINT Verbs and control words in CAPS Refers to the data coming in and out of the process No specific syntax rules Structured English Examples READ Inventory records WHILE NOT End of file DO BEGIN IF IF Quantity in stock is less than Minimum order quantity THEN GENERATE new order ELSE DO nothing END IF END DO READ next prescription SELECT CASE CASE prescription for formulated drug DO send to lab station CASE prescription for off the shelf drug DO send to shelving station CASE prescription for narcotic drug DO send to secure station END CASE Decision Tables Conditions Courses of Action Employee type Hours worked Pay base salary Calculate hourly wage Calculate overtime Produce absence report 1 S Rules 2 H 40 3 H 40 4 H 40 X X X X X X Decision Trees Pay base salary Salaried Calculate hourly wage Produce absence report 1 40 Hourly 2 40 Calculate hourly wage 40 Legend 1 Type of employee 2 Hours worked Calculate hourly wage Calculate overtime wage Network Models Network Decomposition Diagram hubs places where data is stored or processing is done for users at some other location workstations places where a user physically sits and can access the system remotely Hub Connectivity Diagrams simply says what hubs and external networks have to exchange data Network Decomposition Diagram System Hub Workstation Hub Workstation Workstation Set of Workstations Hub Workstation External Network Workstation Hub Connectivity Diagram Hub 35 es mil 50 f eet Hub 30 00 mi le s Hub External Network Simple Example Customer Ordering System Server System Administrator Credit Verification Service Order Takers Server 200 miles Credit Verification Service Data Dictionary Includes descriptions of all pieces of data relationships between pieces of data Purposes eliminate ambiguities identify links between DFDs and ERD clarify how different pieces of data are related serves as a standard reference throughout the project specify what is contained in data stores and flows What needs to be defined Data flows Entities Data stores Relationships are collections of Data elements are collections of correspond to Attributes Basic parts of a definition Name that appears on the diagram Type data flow data store entity etc Description text Synonyms other names used for same thing What it contains What it is contained in Constraints data type Data Flow Definition Name that appears on the diagram Type data flow Description text Synonyms What it contains list of data elements lower level data flows What it is contained in data flow in higher level diagram Constraints source and destination Example Data Flow Definition Name Customer Record Type data flow Description The customer information that needs to be stored in the customer DB Synonyms none What it contains data elements customer ID customer name customer address customer phone lower level data flows none What it is contained in none Constraints Source Process 5 Create Customer Record Destination Data Store D3 Customer Master Data Store Definition Name that appears on the diagram including ID Type data store Description text Synonyms What it contains list of data elements What it is contained in n a Constraints physical form if known Example Data Store Definition Name Customer Master Type data store Description Information on all customers who have provided this information when placing an order Synonyms none What it contains data elements customer ID customer name customer address customer phone What it is contained in n a Constraints form is a database table Data Element Definition Name does not appear on the diagram Type data element Description text Synonyms other data elements and attributes What it contains n a What it is contained in data stores and data flows Constraints format length valid values Example Data Element Definition Name customer name Type data element Description The last name of a customer who has at one time placed an order Synonyms attribute Customer name What it contains n a What it is contained in data flow Customer Record data store Customer Master Constraints must be a character string with maximum length 15 Entity Definition Name that appears on the diagram Type entity Description text Synonyms What it contains attributes What it is contained in n a Constraints identifier Example Entity Definition Name Customer Type entity Description Any individual who has at one time placed an order and purchased goods Synonyms none What it contains attributes Customer ID Name Address Phone What it is contained in n a Constraints Customer ID must be unique Relationship Definition Name that appears on the diagram Type relationship Description text Synonyms What it contains attributes including key attributes of participating entities What it is contained in n a Constraints cardinality degree operational constraints Example Relationship ERD Customer ID Name DFD Phone Address 8 Charge Customer Purchase CUSTOMER Account Information owner type Customer Information Purchase Information Has account number ACCOUNT balance D5 Customer Accounts Example Relationship Definition Name Has Type relationship Description Associates individual customers with the credit accounts they have with this business that they can use to purchase goods Synonyms data store D5 Customer Accounts What it contains attributes Customer Customer ID Account account number owner type What it is contained in n a Constraints binary many to one mandatory for accounts but not customers Attribute Definition Name that appears on the diagram Type attribute Description text Synonyms other attributes and data elements What it contains n a What it is contained in entities and relationships Constraints format length valid values Example Attribute Definition Name Name Type attribute Description The last name of a customer who has at one time placed an order Synonyms data element customer name What it contains none What it is contained in entity Customer Constraints must be a character string with maximum length 15