DB class: Overview of Technical Specification Design Concepts

Overview of Design Concepts: What is a Technical Specification?

Following is a brief summary of some of the concepts on technical specification and design that we are working on in class:

Remember these distinctions:

a functional specification answers questions such as "What screens do the users see?", "What kind of reports does the user need?", "Who will be using this system?" Functional specifications are typcially written by analysts who are specialists in a particular industry or field, but who are not necessarily programmers or technical staff.
a technical specification answers questions such as "What is the operating system for this application?", "What is the database environment to be used?", and "How many tables are in the database and how are they defined?" Technical specifications are typically written by computer department staff, and usually written in conjunction with the analyst(s) and/or users who prepared the functional specifications. If the functional specification is written correctly, the programmer who writes the technical specification should not need to understand the industry per se.

Following are some things to consider when you are working on a technical specification:

What are the hardware and software requirements to run this system? (In our case, we are using MS Access on a PC; be sure to specify a minimum, such as 500 MB, of disk space to store the data, based on your rough calculations.)
List all of the tables to be included in the database and a brief description (one or two sentences) to describe each table.
For each table, describe the file structure (see below) **
List the relationships among the tables. (This is most commonly done as a graphic but you may write it out if you prefer.)

** File Structures For each table, a good technical specificaion includes a list of the fields with the at least the following information for every field: ** see below for a sample

field name: a brief name which is easy to remember (e.g. "artist_name")
field description: a description of the information (e.g. "the name of the artist")
field data type: character, numeric, logical, date, or other; specifiy any specific data type such as a URL or an image. For example, the artist's name would be a character field.
field length: This applies to character and numeric fields. Numeric fields can be described with a specific length for integers (e.g. "8") or with the number of places represented past the decimal (e.g. "6,2" for a number such as 999.99). Character field lengths are specified with an integer, e.g. the artist_name field could be set with a length of 30.
remarks: Be sure to list any important validation rules here. For example, if the field contains the room number in a hotel reservation system, be sure that the room number applies to an actual room. Indicate here whether a field is a primary key (and if it is a foreign key, if you know that yet). Also, specifiy here if a field should be checked against another table (e.g. the artist's name should be validated against the table containing a list of artists on file).

There are many additional things to consider, depending on the nature of the database system that you are designing. But this is a start !!

** Sample File Structure

Artist Table: This table contains a list of the artists (painters and sculptors) represented by this gallery. Data fields include:

field name	field description	data type	field length	remarks
artist_name	the full name of the artist	character	30	Stored as "last, first" e.g. "Pollack, Jackson". This field is the primary key for this table. This field is a foreign key for the table of paintings.
artist_school	the school or style this artist is associated with primarily	character	15	This field should be checked against a list of values e.g. abstract, Baroque, Impressionist, etc.
artist_born	year or approximate year of the artist's birth	character	4	Use century or mid-century approximations where necessary. Be sure this date does not exceed the current year.
artist_death	year or approximate year of the artist's death	character	4	Use century or mid-century approximations where necessary. Be sure this date does not exceed the current year.
artist_nationality	the nationality this artist is associated with primarily	character	15	This field should be checked against a list of values e.g. American, Mexican, Flemish, etc.