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Section 10Data Dictionary - Process Descriptors 1 10 THE DATA DICTIONARY : Process Descriptors And Franchise Colleges By MANSHA NAWAZ.

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Presentation on theme: "Section 10Data Dictionary - Process Descriptors 1 10 THE DATA DICTIONARY : Process Descriptors And Franchise Colleges By MANSHA NAWAZ."— Presentation transcript:

1 Section 10Data Dictionary - Process Descriptors 1 10 THE DATA DICTIONARY : Process Descriptors And Franchise Colleges By MANSHA NAWAZ

2 Section 10Data Dictionary - Process Descriptors 2 Aim –to be able to construct an internal process mini-spec using structured english Objectives –to identify the necessary sequence of actions –to identify any optional paths of action –to identify any possible iterative actions –to record using given syntax Process Descriptors

3 Section 10Data Dictionary - Process Descriptors 3 Process descriptors in a data dictionary internal process mini-specs vocabulary of structured english sequence, selection & iteration local variables Lecture Outline

4 Section 10Data Dictionary - Process Descriptors 4 Programmers –you will have awareness of structured english Non-Programmers –descriptions are sufficient Also consideration –storyboards –screen design –bullet point description –address what needs to be done for the process NOTE

5 Section 10Data Dictionary - Process Descriptors 5 The connection between the DFD and DD for processes is as follows: –we record a Process Specification for each process on the DFD that isn’t exploded. English is very ambiguous and would lead to long-winded and unclear process specifications. We want something clearer and more concise. Structured English is widely used in structured methods. Data Dictionary – Process Descriptors

6 Section 10Data Dictionary - Process Descriptors 6 Process Descriptors DATA DICTIONARY: PROCESS DESCRIPTORS Name: Description: Data Inputs: Data Outputs: Variables: Mini-Spec: Show how something is to be done within a process Techniques covered is based the below form Mini Spec is where we describe the action in terms of an algorithm or structured english Structured English revolving around sequence, selection & iteration instructions

7 Section 10Data Dictionary - Process Descriptors 7 Mini Spec or Process Specification is a form of English with a limited number of constructs and a limited vocabulary. Most programs, like data structures, are made up of: Sequence do the following in this order Selection do this or that depending on... Iteration keep doing this until... Within the Mini-Spec or process specifications we will use: Imperative verbs, like multiply, print, add, create or update Data dictionary terms member, book.author, order reserved words IF...THEN, READ Mathematical symbols Labels A little English or text for readability According to convention, data dictionary terms are underlined and construct words are written in CAPITALS. Mini Spec - Structured English

8 Section 10Data Dictionary - Process Descriptors 8 ambiguous –x and (y or z) OR –(x and y) or z? vague –what is a good payment history? too long “customers who place more than £10,000 of orders per year and have a good payment history or have been with us more than 20 yrs are to receive 10% discount on all orders” Problems with English Text Solution – Use Structured English Text Sequence - Selection - Iteration

9 Section 10Data Dictionary - Process Descriptors 9 A series of imperative statements, for example: Calculate-Discount Get price given item-no Multiply quantity by price giving gross Multiply gross by 0.1 giving discount Invoice-total = gross – discount price, item-no, quantity, gross, discount and invoice-total are all DD terms, whose meanings have already been defined. Sequence

10 Section 10Data Dictionary - Process Descriptors 10 Process specifications are often written in a hierarchical, top-down fashion, like the way sets of DFDs are developed by explosion. To this end, DO followed by a label is used to carry out a block of statements at a lower level. ….….….….….…. DO Calculate-Invoice-Total ….….….….….…. Calculate-Invoice-Total Get price given item-no Multiply quantity by price giving gross DO Calculate-Discount Invoice-total = gross – discount ….….….….….…. Sequence cont..

11 Section 10Data Dictionary - Process Descriptors 11 Given the top-level statement DO Stir-Fry-Meal and using Structured English, write two DO statements to specify the process Stir-Fry-Meal, which consists of 2 parts, one to select the main ingredient and one to cook the dish. Answer Stir-Fry-Meal DO Select-Main-Ingredient DO Cook-Dish Sequence Example

12 Section 10Data Dictionary - Process Descriptors 12 used when more than one possible action IF condition1 reserved word action1 indentation ELSE (condition2) not condition in () action2 indentation ENDIF end the selection also use ELSEIF or CASE Selection

13 Section 10Data Dictionary - Process Descriptors 13 This shows alternatives and uses the construct words IF, ELSE and ENDIF. IF delivery is local Add £5 to invoice-total ELSE (delivery not local) Add £20 to invoice-total ENDIF Note how indentation is used to help the meaning. Also, note how the reverse of the original condition is stated for the ELSE part for clarity. Whilst optional, this is good practice. Selection cont…

14 Section 10Data Dictionary - Process Descriptors 14 Using Structured English write an IF … ELSE … ENDIF statement to specify the process Select- Main-Ingredient. If a guest is a meat eater, the main ingredient will be chicken. Otherwise the main ingredient will be vegetables. DD terms already defined are Guest, Carnivore and Main-Ingredient. Answer Select-Main-Ingredient IF Guest is Carnivore Main-Ingredient = ‘Chicken’ ELSE Main-Ingredient = ‘Vegetables’ ENDIF Selection – IF

15 Section 10Data Dictionary - Process Descriptors 15 We can nest IF constructs, for example: IF delivery is local IF Order-value > £50 Add £1 to Invoice-Total ELSE Add £5 to Invoice-Total ENDIF ELSE Add £20 to Invoice-Total ENDIF Selection – Nested IF

16 Section 10Data Dictionary - Process Descriptors 16 IF constructs: IF X = 1 Add B to A ENDIF IF X = 2 Add C to A ELSE Add D to A ENDIF Case constructs: DO CASE CASE X = 1 Add B to A CASE X = 2 Add C to A OTHERWISE Add D to A ENDCASE Rather than use a series of IF constructs we can use the CASE.construct for clarity: Selection – Case

17 Section 10Data Dictionary - Process Descriptors 17 This is used for loops or repetitions –when action to be carried –Repeat Until or Do While Iteration REPEAT reserved word statement1 indentation... UNTIL condition end condition example REPEAT DO Calculate-Invoice-Total Print Invoice UNTIL no more Sales-Details DOWHILE condition reserved word statement1 indentation... ENDDO end condition example DOWHILE more Sales-Details DO Calculate-Invoice-Total Print Invoice ENDDO

18 Section 10Data Dictionary - Process Descriptors 18 Using Structured English specify the process Cook-Dish. You need a sequence for adding oil to the wok, heating the oil, then adding the ingredients, followed by an iteration while you stir fry the ingredients until they’re cooked. DD terms already defined are Oil, Wok and Cooked. Iteration Example Cook-Dish Add Oil to Wok Heat Oil Add Ingredients to Wok DO WHILE Ingredients NOT Cooked Heat Oil Cook Ingredients ENDDO Answer

19 Section 10Data Dictionary - Process Descriptors 19 sometimes a local variable is used –placeholder for a value & make clearer defined within the process specification SET subtot = 0 REPEAT Add (qty*unitprice) to subtot UNTIL no more orderitems SET total = subtot Local Variables

20 Section 10Data Dictionary - Process Descriptors 20 DO Stir-Fry-Meal Stir-Fry-Meal DO Select-Main-Ingredient DO Cook-Dish Select-Main-Ingredient DO CASE CASE Guest is Carnivore: Main-Ingredient = ‘Chicken’ CASE Guest is Fish-Eater Main-Ingredient = ‘Prawns’ OTHERWISE Main-Ingredient = ‘Vegetables’ END CASE Cook-Dish Add Oil to Wok Heat Oil Add Ingredients to Wok DO WHILE Ingredients NOT Cooked Heat Oil Cook Ingredients ENDDO Complete Structured English

21 Section 10Data Dictionary - Process Descriptors 21 –Data Dictionary lecture 08 lecture 08 Data Stores - Structures & Elements lecture 08 lecture 08 Data Flow - Structures & Elements lecture 08 lecture 08 Data Stores and Flow Usage lecture 09 lecture 09 Process Descriptions lecture 10 lecture 10 –NORMALISATION lecture 11 lecture 11 Database Tables derived from Data Store Descriptions Document : Design Specification

22 Section 10Data Dictionary - Process Descriptors 22 –Data Dictionary lecture 08 lecture 08 Data Stores - Structures & Elements lecture 08 lecture 08 Data Flow - Structures & Elements lecture 08 lecture 08 Data Stores and Flow Usage lecture 09 lecture 09 Process Descriptions lecture 10 lecture 10 –For each process list »Process Usage & Mini Spec »Process Screen Shot Document : Data Dictionary

23 Section 10Data Dictionary - Process Descriptors 23 Process specifications are formed by combining sequence, selection and iteration constructs. –DO is used to structure the specification, using labels. –Construct words are written in CAPITALS. –Data dictionary terms are underlined. –Imperative verbs are used, plus a little English for readability and some mathematical notation. –Process specifications are not at the detailed program coding level. Structured English is recommended as a process specification tool because: –It uses standard constructs and rules, making it clear and concise. –It uses data dictionary terms, making it precise. –To remove ambiguity, it uses nesting and the normal computer rules of precedence, ie ANDs are evaluated before ORs. Summary

24 Section 10Data Dictionary - Process Descriptors 24 Further Reading Notes from Annette Marshall on Data Dictionary


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