DFD - Data Flow Diagram

This is a diagram that shows how the data manipulated by a system flows through the various processes. You'll see one of several types of symbols in a DFD... a process, a data store, or an external entity. These symbols are connected by arrowed lines showing how the data moves from a data store or external entity, through a process, and back to a data store or external entity. A DFD is NOT a flow chart! A flow chart actually describes a process, whereas in a DFD the entire process is simply denoted by a symbol.

ERD - Entity Relationship Diagram

An Entity Relationship Diagram shows the various data tables and interfaces in a system, and how they are connected together. The "entities" are database tables (usually represented by blocks), and the relationships are denoted by lines connecting the entities. If you've ever used Access or Visual FoxPro and you've seen the table relationship diagrams, those are simplified ERDs. Special symbols are used in the connecting lines so that you know not only that two tables are related, but how they're related.

Functional Specification

Same as Functional System Design (FSD)

FSD - Functional System Design

This is the "floorplan" of a system... it describes the following in high-level terms: 

  • The major data sources and interfaces of the system.

  • The major functions of the system.

  • The interrelationships of these functions and data sources.

  • The architecture to be used (platform, languages, etc). 

MDD - Module Design Document

A technical design documnet for a specific module. This is a very low-level specification.

PLC - Project Life Cycle

see SDM.

SDM - System (or Standard) Development Methodology

Basically, what you've been reading. An SDM is a standardized method of managing system development which consists of procedures, a document framework, and coding standards. An SDM provides a consistent set of guidelines so that less of your time is spent on the process and more on the execution.

Technical Specification

Same as Technical System Design (TSD)

TSD - Technical System Design

The TSD is the low-level specification for an overall system. Properly, it consists of two parts: The TSD document itself, which specifies the overall framework of the system, and multiple MDD documents, which detail the specifications for individual modules.


The Unified Modeling Language. This is a flexible set of diagramming conventions created by Grady Booch, Ivar Jacobson, and Jim Rumbaugh. The specification is owned and managed by the Object Management Group. I have a brief overview here.

Swim Lane Diagram Document Templates

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