abstraction

Abstraction is the removal of details in such a way as to broaden applicability to a wider class of situations, while preserving the important properties and essential nature of concepts or subjects. By removing these details, we remove differences and, therefore, change the way we view these concepts or subjects, including seeing similarities that were not apparent or even existent before. For example, we may abstract Employee and Consumer into the more generic concept of Person. A Person can play many Roles, two of which are Employee and Consumer.

alternate key

An alternate key is a candidate key that although unique, was not chosen as the primary key, but still can be used to find specific entity instances.

architect

An experienced and skilled designer responsible for system and/or data architecture supporting a broad scope of requirements over time, beyond the scope of a single project. The term implies a higher level of professional experience and expertise than an analyst, designer, or developer.*

associative entity

An entity or table that resolves a many-to-many relationship between two other related entities or tables.*

business analyst

An IT or business professional responsible for understanding the business processes and the information needs of an organization, for serving as a liaison between IT and business units, and acting as a facilitator of organizational and cultural change.*

candidate key

A candidate key is one or more data elements that uniquely identify an entity instance. Sometimes a single data element identifies an entity instance, such as ISBN for a book, or Account Code for an account. Sometimes it takes more than one data element to uniquely identify an entity instance. For example, both a Promotion Code and Promotion Start Date are necessary to identify a promotion.

cardinality

Cardinality defines the number of instances of each entity that can participate in a relationship. It is represented by the symbols that appear on both ends of a relationship line. It is through cardinality that the data rules are specified and enforced. Without cardinality, the most we can say about a relationship is that two entities are connected in some way through a rule. For example, where we know that Person and Company have some kind of relationship, but we don’t know much more than this.

class word

A class word is the last term in a data element name, such as Amount, Code, and Name. Class words allow for the assignment of common domains.

conformed dimension

A conformed dimension is one that is shared across the business intelligence environment. Customer, Account, Employee, Product, Time, and Geography are examples of conformed dimensions. Ralph Kimball made the term popular. It requires the modeler to design the conformed dimension with a much broader perspective than just the requirements for a single data mart.

data element

A data element is a property of importance to the business. Its values contribute to identifying, describing, or measuring instances of an entity. The data element Claim Number identifies each claim. The data element Student Last Name describes the last name of each student. The data element Gross Sales Value Amount measures the monetary value of a transaction.

data model

A data model is a wayfinding tool for both business and IT professionals, which uses a set of symbols and text to precisely explain a subset of real information to improve communication within the organization, thereby leading to a more flexible and stable application environment.

data modeler

A business systems analyst who identifies data requirements, defines data, and develops and maintains data models.*

data modeling

Data modeling is the process of building a data model. More specifically, data modeling is the set of techniques and activities that enable us to capture the data to support the structure and operations of an organization, as well as a proposed information solution that will enable the organization to achieve its goals. The process requires many skills, such as listening ability, courage to ask lots of questions, and even patience.

database administrator (DBA)

The IT professional role responsible for database administration, the function of managing the physical aspects of data resources, including database design and integrity, backup and recovery, performance and tuning.*

denormalization

Denormalization is the process of selectively violating normalization rules and reintroducing redundancy into the model (and therefore, the database). This extra redundancy can reduce data retrieval time, which is the primary reason for denormalizing. We can also denormalize to create a more user-friendly model. For example, we might decide to denormalize company information into an entity containing employee information, because usually when employee information is retrieved, company information is also retrieved.

developer

A person who designs, codes and/or tests software. Synonymous with software developer, systems developer, application developer, software engineer, and application engineer.*

dimension

A dimension is reference information whose purpose is to add meaning to the measures. All of the different ways of filtering, sorting, and summing measures make use of dimensions. Dimensions are often, but not exclusively, hierarchies.

dimensional model

A dimensional model focuses on capturing and aggregating the metrics from daily operations that enable the business to evaluate how well it is doing by manipulating the numbers. For example, examining the measure Gross Sales Value Amount at a day level and then, after getting the answer, looking at Gross Sales Value Amount at a month or year level, or at a product or brand level, or a city or country level. The dimensional model is all about playing with numbers.

domain

A domain is the complete set of all possible values that a data element may be assigned. A domain is a set of validation criteria that can be applied to more than one data element. For example, the domain ‘Date’, which contains all possible valid dates, can be assigned to any of these data elements:

Employee Hire Date

Order Entry Date

Claim Submit Date

Course Start Date

enterprise data model

An Enterprise Data Model (EDM) is a subject-oriented and integrated data model containing all of the data produced and consumed across an entire organization. Subject-oriented means that the concepts on a data model fit together as the CEO sees the company, rather than how any individual functional or department heads see their view of the company. There is one Customer entity, one Order entity, etc. Integration goes hand in hand with subject-orientation. Integration means that all of the data and rules in an organization are depicted once and fit together seamlessly. Every data element has a single definition and name. Integration implies that with this single version of the truth comes a mapping back to the chaotic real world.

entity

An entity represents a collection of information about something that the business deems important and worthy of capture. A noun or noun phrase identifies a specific entity. It fits into one of several categories - who, what, when, where, why, or how.

entity instance

Entity instances are the occurrences or values of a particular entity. Think of a spreadsheet as being an entity, with the column headings representing the pieces of information about the entity. Each spreadsheet row containing the actual values represents an entity instance. The entity Customer may have multiple customer instances with names Bob, Joe, Jane, and so forth. The entity Account can have instances of Bob’s checking account, Bob’s savings account, Joe’s brokerage account, and so on.

Extensible Markup Language (XML)

Extensible Markup Language (XML) is a specification for storing information, and for describing the structure of that information. XML is both useful and powerful for the same reasons any data model is useful and powerful: it is easy to understand, can be technology-independent, and enables representing complex problems with simple syntax. Similar to distinguishing subject area models from logical data models from physical data models, XML distinguishes the data content about formatting (e.g. blue, Arial, 15 point font) from rules.

factless fact

A fact table that does not contain any facts (i.e. measures) is called a factless fact. Factless facts count events by summing relationship occurrences between the dimensions. For example, a fact table called Attendance contains no measures. It links to the Student, Course, and Semester dimensions with the goal of counting relationship occurrences of how many students take a particular course in a particular semester.

foreign key

A foreign key is a data element that provides a link to another entity. A foreign key allows a database management system to navigate from one entity to another. For example, we need to know who owns an Account, so we would want to include the identifier of the customer to whom it belongs in the entity. The Customer Id in Account is the primary key of that Customer in the Customer entity. Using this foreign key back to Customer enables the database management system to navigate from a particular account or accounts, to the customer or customers that own each account. Likewise, the database can navigate from a particular customer or customers, to find all of their accounts.

grain

The grain is the meter’s lowest level of detail. It should be low enough that the answers to all of the business questions within the scope of the dimensional model are derivable. It is generally a good practice to define the measures and grain as early as possible in the requirements process. In the ice cream model in this book, the grain is Ice Cream Container and Day.

index

An index is a pointer to something that needs to be retrieved. An analogy often used is the card catalog, which in the library, points you to the book you need. The card catalog will point you to the place where the actual book is on the shelf, a process that is much quicker than looking through each book in the library until you find the one you need. Indexing works the same way with data. The index points directly to the place on the disk where the data is stored, thus reducing retrieval time. Indexes work best on data elements whose values are requested frequently but rarely updated.

key

There is often a need to find specific entity instances using one or more data elements. Those data element(s) that allow us to find specific entity instances are known as keys. The Library of Congress assigns an ISBN (International Standard Book Number) to every book. A particular tax identifier can help us find an organization. The key Account Code can help us find a particular account.

logical data model (LDM)

A logical data model (LDM) is a business solution to a business problem. It is how the modeler captures the business requirements without complicating the model with implementation concerns such as software and hardware.

measure

A measure is a data element that may be manipulated in or is the result of a calculation (e.g., sum, count, average, minimum, and maximum).

metadata

Metadata is text, voice, or image that describes what the audience wants or needs to see or experience. The audience could be a person, group, or software program. Metadata is important because it aids in clarifying and finding the actual data.

A particular context or usage can turn what we traditionally consider data into metadata. For example, search engines allow users to enter keywords to retrieve web pages. These keywords are traditionally data, but in the context of search engines they play the role of metadata. In much the same way that a particular person can be an Employee in one role and a Customer in another role, text, voice, or image can play different roles - sometimes playing ‘data’ and sometimes playing ‘metadata’, depending on what is important to a particular subject or activity.

meter

A meter is an entity containing a related set of measures. It is not a person, place, event, or thing, as we find on the relational model. Instead, it is a bucket of common measures. As a group, common measures address a business concern, such as Profitability, Employee Satisfaction, or Sales. The meter is so important to the dimensional model that the name of the meter is often the name of the application.

natural key

A natural key is what the business sees as the unique identifier for an entity.

normalization

Normalization is the process of applying a set of rules with the goal of organizing something. With respect to data elements, normalization ensures that every data element is single-valued and provides a fact completely and only about its primary key. ‘Single-valued’ means a data element must contain only one piece of information. If Consumer Name contains Consumer First Name and Consumer Last Name, for example, we must split Consumer Name into two data elements - Consumer First Name and Consumer Last Name. ‘Provides a fact’ means that a given primary key value will always return no more than one of every data element that is identified by this key. If a Customer Identifier value of ‘123’ for example, returns three customer last names (‘Smith’, ‘Jones’, and ‘Roberts’), this violates the dependency definition. ‘Completely’ means that the minimal set of data elements that uniquely identify an instance of the entity is present in the primary key. If, for example, there are two data elements in an entity’s primary key, but only one is needed for uniqueness, the data element that is not needed for uniqueness should be removed from the primary key. ‘Only’ means that each data element must provide a fact about the primary key and nothing else. That is, there can be no hidden dependencies.

object

In an object-oriented design, synonymous with a class; an entity that combines descriptions of the common behavior of like instances along with their common data attributes. Objects may be business objects, interface objects, or control objects.*

ontology

An ontology is a formal way of organizing information. It includes putting ‘things’ into categories and relating these categories with each other. The most quoted definition of an ontology is Tom Gruber’s definition: “Explicit specification of a conceptualization.” In other words, an ontology is a model – a model being a simplification of something complex in our environment using a standard set of symbols.

partition

In general, a partition is a structure that divides or separates. Specific to the physical design, partitioning is used to break a table into rows, columns or both. There are two types of partitioning - vertical and horizontal. To understand the difference between these two types, visualize a physical entity in a spreadsheet format where the data elements are the columns in the spreadsheet and the entity instances are the rows. Vertical means up and down. So vertical partitioning means separating the columns (the data elements) into separate tables. Horizontal means side to side. So horizontal partitioning means separating rows (the entity instances) into separate tables.

physical data model (PDM)

The Physical Data Model (PDM) is the Logical Data Model modified for a specific set of software or hardware. The PDM often gives up perfection for practicality, factoring in real concerns such as speed, space, and security.

primary key

A primary key is a candidate key that has been chosen to be the unique identifier for an entity.

program

A program is a large, centrally organized initiative that contains multiple projects. It has a start date and, if successful, no end date. Programs can be very complex and require long-term modeling assignments. Examples include a data warehouse, operational data store, and a customer relationship management system.

project

A project is a plan to complete a software development effort, often defined by a set of deliverables with due dates. Examples include a sales data mart, broker trading application, reservations system, and an enhancement to an existing application.

project manager

A person who manages project resources and activities in order to deliver the agreed-upon project outputs.*

recursive relationship

A relationship between instances of the same entity. For instance, one organization can report to another organization.*

Note: PowerDesigner refers to these as ‘reflexive’ relationships

relational model

A relational model captures how the business works and contains business rules, such as “A Customer must have at least one Account”, or “A Product must have a Product Short Name.”

relationship

Rules are captured on our data model through relationships. A relationship is displayed as a line connecting two entities. If the two entities are Employee and Department, the relationship may capture the rules “Each Employee must work for one Department” and “Each Department may contain many Employees.”

semi-structured data

Semi-structured data is equivalent to structured data with one minor exception: Semi-structured data requires looking at the data itself to determine structure, as opposed to structured data which only requires examining the data element name. Semi-structured data is one processing step away from structured data.

slowly changing dimension (SCD)

Reference entity instances will experience changes over time, such as a person moving to a new address, or product name changing, or an account description being updated. On dimensional models, there is a special term that describes how to handle changing values: Slowly Changing Dimension (SCD). An SCD of Type 1 means only the most current information will be stored. An SCD of Type 2 means the most current along with all history will be stored. And an SCD of Type 3 means the most current and some history will be stored.

snowflake

A snowflake occurs when there are one or more tables for each dimension. Sometimes the snowflake structure is equivalent to the dimensional logical model, where each level in a dimension hierarchy exists as its own table. Sometimes, in a snowflake there can be even more tables than exist on the dimensional logical model. This is because vertical partitioning is applied to the dimensional model.

spreadsheet

A spreadsheet is a representation of a paper worksheet, containing a grid defined by rows and columns, where each cell in the grid can contain text or numbers.

stakeholder

A stakeholder is a person who has an interest in the successful completion of a project. Examples of stakeholders are project sponsors, business users, and team leads.

star schema

A star schema is the most common dimensional physical data model structure. A star schema results when each set of tables that make up a dimension is flattened into a single table. The fact table is in the center of the model and each of the dimensions relate to the fact table at the lowest level of detail. A star schema is relatively easy to create and implement, and visually appears elegant and simplistic to both IT and the business.

structured data

Structured data is any data named with a simple class word. ‘Simple’ means if data can be broken down, it can only be broken down further through normalization.

Examples:

Order Entry Date

Customer Name

Gross Sales Value Amount

subject area model (SAM)

A Subject Area Model is a set of symbols and text representing the key concepts and rules binding these key concepts for a specific business or application scope, for a particular audience, that fits neatly on one page. It could be an 8 ½ x 11, 8 ½ x 14, or similar sized paper, but it cannot be a plotter-sized piece of paper. Limiting the subject area model to one page is important because it forces the modeler and participants to select only key concepts.

subject matter expert (SME)

A person with significant experience and knowledge of a given topic or function.*

surrogate key

A surrogate key is a primary key that substitutes for a natural key, which is what the business sees as the unique identifier for an entity. It has no embedded intelligence and is used by IT (and not the business) for integration or performance reasons. Surrogate keys are useful for integration, which is an effort to create a single, consistent version of the data. Applications such as data warehouses often house data from more than one application or system. Surrogate keys enable us to bring together information about the same entity instance that is identified differently in each source system. Surrogate keys are also efficient. You’ve seen that a primary key may be composed of one or more attributes of the entity. A single surrogate key is more efficient to use than having to specify three or four (or five or six) attributes to locate the single record you’re looking for.

taxonomy

A taxonomy is an ontology in the form of a tree. A tree is when a child only has a single parent and a parent can contain one or more children. If a child can have more than one parent, than the child is typically repeated for each parent. Examples of kinds of taxonomies are product categorizations, supertype/subtype relationships on a relational data model, and dimensional hierarchies on a dimensional data model.

use case

In object-oriented analysis, a work flow scenario defined in order to identify objects, their data, and their methods (process steps). *

user

A person who enters information into an application or queries the application to answer business questions and produce reports.

view

A view is a virtual table. It is a dynamic “view” or window into one or more tables (or other views) where the actual data is stored. A view is defined by a query that specifies how to collate data from its underlying table(s) to form an object that looks and acts like a table but doesn’t physically contain data. A query is a request that a user (or reporting tool) makes of the database, such as “Bring me back all Customer Ids where the Customer is 90 days or more behind in their bill payments.” The difference between a query and a view, however, is that the instructions in a view are already prepared for the user (or reporting tool) and stored in the database as the definition of the view, whereas a query is not stored in the database and may need to be written each time a question is asked.

wayfinding

Wayfinding encompasses all of the techniques and tools used by people and animals to find their way from one site to another. If travelers navigate by the stars, for example, the stars are their wayfinding tools. Maps and compasses are also wayfinding tools. All models are wayfinding tools. A model is a set of symbols and text used to make a complex concept easier to grasp. The world around us is full of obstacles that can overwhelm our senses and make it very challenging to focus only on the relevant information needed to make intelligent decisions. A map helps a visitor navigate a city. An organization chart helps an employee understand reporting relationships. A blueprint helps an architect communicate building plans.

attribute (1)

An Attribute within an entity in a data model.

attribute (2)

A type of property available on an Object or Sub-object in PowerDesigner, where the property can have a single value. For example, every type of Object has a Name property. You may see a list of these attributes when configuring Display Preferences.

collection

A type of property available on an Object or Sub-object in PowerDesigner, where the property can form a link to one or more other Objects or Sub-objects. For example, every type of Object has a collection that lists related Business Rules. You may see a list of collections when configuring Display Preferences.

composer

A special PowerDesigner license with limited privileges, that allows non-modelers to edit the comments, descriptions, and annotations of objects directly in the PowerDesigner Portal.

composite object

Any object that has a collection of sub-objects. For example, an entity can have a collection of attributes, a business process can have a collection of sub-processes.

conversion table

A table containing a list of strings that may appear in object names, matched with equivalent (generally shorter) strings with which to replace them when generating object codes.

data item

An elementary piece of information, which represents a fact or a definition in an information system, and which may or may not have any eventual existence as a modeled object. Data Items are an integral part of the Conceptual Data Model.

dependency

A link between any two ‘things’ in PowerDesigner. A ‘thing’ can be a diagram, object, or sub-object. These links can be created manually by the modeler, but the majority are created when you generate a model, add symbols to diagrams, populate collections, or create shortcuts or replicas. See also internal dependency and external dependency.

dependency matrix

You can create dependency matrices to review and create links between any kind of objects. You can create an individual matrix from the Browser or define a matrix in a resource file, for reuse.

document

A generic term for any model or file referenced by the PowerDesigner Browser or the repository.

entity attribute

See Attribute (1)

Term used in drop-down lists of object types, such as when selecting objects for a list report or dependency matrix

extended attribute

An attribute that has been added to PowerDesigner via an extension.

extended collection

A collection that has been added to PowerDesigner via an extension.

extended dependency

See Traceability Link.

extended objects / sub-objects / links

User-defined objects, sub-objects, and dependencies. Extended objects and extended links are available by default in the free model, and can be added to any other type of model through the Profile category in the model's resource file or in an extension file. In the Free Model, these objects and links can represent anything you want them to, using the stereotype property to categorize them.

extension

A type of resource file that allows you to extend the properties of objects and sub-objects in a model, and also to create extended objects and links.

external dependency

A dependency between two models, or between objects in two models.

framework

A standard feature of a project which provides the ability to direct how your project must be modeled and lists the documents that are needed. It can also contain default content for new projects, and define actions, providing some simple automation capabilities, such as building or editing a set of subject areas.

generate

The act of creating a new model by transferring and converting the content of an existing model. The term also refers to updating a model using the same mechanism. By default, generating a model will create a dependency between an object or sub-object in the original model, and the corresponding object or sub-object in the generated model.

glossary

The Glossary feature allows you to share a common vocabulary and business rules. The vocabulary is expressed as a hierarchy of Terms; a Term is a word or phrase that forms part of a controlled vocabulary.

grid editor

A standard editing technique in PowerDesigner, where lists of objects or sub-objects can be edited, sorted, and filtered in a consistent way. For example, list reports, lists of objects, collections, and lists of sub-objects.

identifier

The PowerDesigner term for key♦ in the CDM and LDM.

impact and lineage analysis

The standard PowerDesigner feature that analyzes dependencies to visualize the context of an object or sub-object.

inheritance

The PowerDesigner term for a grouping of subtype entities.

inheritance link

The PowerDesigner term for the link between a subtype entity and an inheritance.

internal dependency

A dependency between two objects or sub-objects in the same model.

library

A repository-based feature that allows the organization to share reference models and other shared material with all users with a repository connection.

link and sync

The generic term for the ability of PowerDesigner to create, manage, and review dependencies.

metamodel

The data model that describes the objects supported by PowerDesigner.

naming template

A set of characteristics of object names, such as ‘mixed case’, maximum 256 characters, no accent characters permitted’.

object

The key building blocks of PowerDesigner models. All the objects in a model are listed as items in the Browser and they may also appear as symbols in your diagrams.

object property sheet

The standard mechanism in PowerDesigner for editing the properties (see property) of objects, which present object properties on tabs. The content and layout of the tabs can be customized.

You can open an object property sheet in any of the following ways:

·         In the Browser, double-click the object symbol or its entry.

·         Right-click the object symbol or its Browser entry, and select ‘Properties’.

·         Select the object from an object list or in the property sheet of its parent object, and click the ‘Properties’ tool.

·         Select an object symbol and press <Alt+Enter>.

project

A ‘container’ for managing related models and external files. A project can be checked in to the repository as an object in its own right. The dependencies between models in a project can be illustrated in a project diagram.

project diagram

A project diagram allows you to display documents in a project, and the dependencies between them.

property

A discrete item of information that can be captured about an Object or Sub-object in PowerDesigner. See also collection and attribute (2).

property sheet

See Object Property Sheet

reference model

A model that is automatically shared with all users of the PowerDesigner repository via the Library, such as a data dictionary, a PDM containing standard domains, or any model containing objects to share or reference.

reflexive relationship

The PowerDesigner term for a recursive♦ relationship.

replica

Something in a model that is a managed copy of an object or sub-object. Replicas can be edited, and therefore differ from the original object, subject to the limitations imposed in the associated Replication, which maintains the link between the replica and the original object. Replications can be viewed by selecting Model|Replications. Shortcuts can be viewed by selecting Model|Shortcuts.

See also shortcut.

resource file

A file used to define customizations to PowerDesigner, such as additional objects and processes, or the methods for handling a given DBMS. Resource files can be shared via the repository.

shortcut

A reference to an object defined elsewhere, such as in another model or package. Unlike a replica, a shortcut is not an object in its own right.

stereotype

A categorization of a type of object or sub-object. The simplest form of stereotype is a text label on a diagram. At the other extreme, applying a stereotype to an object can completely change the way the object is treated in PowerDesigner. For example, the object could have its own Browser folder, symbol, and properties.

sub-object

A special type of object that can only exist within another object, such as an attribute within an entity.

traceability link

A user-defined link between two model objects (including between objects in different models) via the ‘Traceability Links’ tab of the object's property sheet. These links are used for documentation purposes only, and are not interpreted or checked by PowerDesigner. They can be included in Impact Analysis.

workspace

A working set of folders, projects, and models in the ‘Local’ tab of the Browser. Only one workspace can be open at a time.