aborting a workflow
An ungraceful and immediate teardown of a workflow instance. An aborted workflow that has been previously persisted can be loaded and resumed from its last persistence point. Aborting the workflow simply throws away everything since the last persistence point.
activity
The basic unit of composition within a workflow. An activity represents a single step in a tree of declared objects. Each activity can have its own set of input and output arguments and local variables and accomplishes some useful work.
Activity
The abstract base class for all other activity types in WF.
ActivityAction
A type-safe activity callback mechanism that allows you to pass 0–16 arguments with no return value. The target activity that is executed must match the argument signature of the ActivityAction. This class is derived from ActivityDelegate.
ActivityBuilder
A class that is designed to assist with the construction of activities. It enables the workflow designer to support the declaration of arguments and variables.
ActivityContext
A class that provides an activity with limited access to the WF runtime environment. The runtime environment includes the variables and arguments that are currently in scope for a single execution of an activity. This is the base class for the CodeActivityContext and NativeActivityContext classes that provide varying levels of access to the runtime environment.
Represents a callback mechanism using an activity. This type allows you to define a type-safe callback for an activity. The callback activity to execute is specified at design time when the activity is used. This is the parent class of ActivityAction and ActivityFunc.
ActivityDesigner
A class that visually represents an activity on the workflow designer surface. You must derive from this class when you implement a custom designer for an activity.
ActivityFunc
A type-safe activity callback mechanism that allows you to pass 0–16 arguments with a return value. The ActivityFunc class is similar to the ActivityAction class except it supports a return value while ActivityAction does not. This class is derived from ActivityDelegate.
ActivityInstance
A class that represents the current runtime state of an activity.
arguments
Define the public inputs and outputs of an activity. The Argument class is the base for all arguments. Classes derived from this base (InArgument, OutArgument, InOutArgument) define and restrict the direction of data flowing into and out of an activity.
AsyncCodeActivity
An abstract base class that is used to implement an activity that performs work on a separate thread. This class is derived from the base Activity class.
asynchronous unit of work
A general category of work that an activity might perform. Activities in this category are designed to perform an atomic unit of work but are capable of doing so asynchronously on a separate thread. Although these activities can use a separate thread for part of their work, that work must execute in a relatively short period of time. They are not designed for long-running operations that might take days to complete. The work they perform should be atomic, completing entirely during a single execution of the activity.
atomic unit of work
A general category of work that an activity might perform. This kind of activity encapsulates the logic to perform a unit of work synchronously on the workflow thread. The unit of work that is performed is atomic in the sense that it is completed entirely during a single execution of the activity. It doesn’t need to suspend execution and wait for external input. It is short-lived and doesn’t perform time-consuming operations. It executes synchronously on the workflow thread and doesn’t create or use other threads.
In WCF, a binding describes how messages are exchanged between systems using an endpoint. It is a named stack containing the transport, encoding, and protocols that determine the way that WCF processes inbound and outbound messages on an endpoint.
bookmark
A general mechanism to temporarily suspend execution of an activity until external input is received. When the external input is available, the bookmark is resumed. Bookmarks can also be configured to not block execution of an activity and to be resumed multiple times.
CacheMetadata
A method of the Activity class that creates and validates a full description of the activity. The description includes the arguments, variables, child activities, child delegates, and other implementation details.
canceled activity state
The state that an activity transitions to when cancellation has been requested.
canceling a workflow
The most graceful way to stop execution of an instance. Canceling a workflow triggers any optional cancellation and compensation logic that you have declared within the workflow. It leaves the workflow in the canceled state. A canceled workflow cannot be resumed.
closed activity state
The state that an activity transitions to when it has successfully completed its work. An activity in the closed state cannot be resumed.
CLR
See Common Language Runtime.
CodeActivity
An abstract base class that is used to implement a custom activity. The work that is performed within the custom activity should be short-lived and execute synchronously on the workflow thread. This class is derived from the base Activity class.
Common Language Runtime
The managed runtime environment that permits cross-language .NET development.
The general mechanism by which work that has already been completed is undone.
composite activities
Activities that are designed to support one or more child activities or activity delegates.
composition
A way to implement new activities by combining existing child activities to serve a new specialized purpose.
confirmation
A mechanism to signal that an activity is past the point of execution where compensation is allowed or necessary.
constraints
Custom classes that externally perform validation on an activity.
content-based correlation
Correlation that is based on one or more selectable data elements within a message. This type of correlation uses application data to correlate messages rather than data that is provided by the infrastructure.
context-based correlation
Correlation that is based on fixed and well-known headers in the message that are provided by the infrastructure.
control flow activities
A general category of activities that allow you to make branching and looping decisions with a workflow.
correlation
A mechanism used to associate messages with the correct workflow service instance. Correlation is also used to associate multiple messaging activities with each other within a workflow.
data contract
In WCF, a data contract is one that permits the definition of messages with multiple parameters.
An implementation model that defines the work to be performed using a tree of activities. The relationships between the activities determines the sequence and conditions under which each activity is executed. In a declarative model, imperative code is not used to control the flow of execute between activities.
duplex message exchange pattern
One of the WCF message exchange patterns supported by WF. When using this pattern, each side of the conversation can send out-of-band messages directly to the other side.
durable delay
Refers to a declared delay in a workflow that is persisted to storage during the delay period. When the delay expires, the workflow is reloaded from storage, and processing can continue. The delay is durable in the sense that it is not lost when the workflow is unloaded from memory.
DynamicActivity
An activity class that is used to dynamically construct activities at runtime rather than at design time. A DynamicActivity cannot be compiled into a CLR type. This class is derived from the base Activity class.
EditingContext
A class that is used by the WorkflowDesigner to manage internal designer state. Managed state includes services and context items.
endpoint
In WCF, a place where messages can be sent or received. All messages in WCF are exchanged between endpoints.
ETW
See Event Tracing for Windows.
Event Tracing for Windows
An enhanced Windows tracing facility that provides greater management and viewing of trace events.
executing activity state
The state that all activities begin in. This state indicates that an activity has not yet completed its work. An activity remains in the executing state when it becomes idle.
A general-purpose mechanism to declaratively execute some logic and return a value. Expressions in WF include any activities that return a single value. Expressions allow you to declare code that assigns a value to a property, saves a value to a workflow variable, and so on. Expressions are the small bits of glue code within the declarative workflow model.
extension
See workflow extension.
external data exchange
A WF 3.x mechanism that is used to facilitate communication between the host application and a workflow instance.
faulted activity state
The state that an activity transitions to when an unhandled exception has been thrown or when the activity has been terminated. An activity in the faulted state cannot be resumed.
flow chart modeling style
A style of workflow authoring that uses direct connections between activities to control the flow of execution. Looping and branching decisions are made using activity connections. This is in contrast with the procedural modeling style that adds activities as children of flow-control activities to control the flow of execution.
Flowchart
An activity that defines the flow chart modeling style. Child activities can be added to this activity, and direct connections can be defined between the activities to control the flow of execution.
FlowDecision
An activity that can be used as a child of the Flowchart activity to make branching decisions. This activity enables branching of the flow of execution based on the result of a Boolean condition.
FlowSwitch<T>
An activity that can be used as a child of the Flowchart activity to make branching decisions based on the value of an expression. A different flow of execution can be defined for each possible value of the expression.
A general category of workflows that require interaction with humans. Workflows of this type are typically capable of long-running execution because of the unpredictability of the human interactions.
instance store
The persistence mechanism that is used by WF 4. Regardless of the actual persistence medium, all persistence is accomplished using a component known as an instance store.
InstanceStore
The base class that all instance store components must derive from.
Interop
An activity that is capable of wrapping an existing WF 3.x activity for execution in the WF 4 runtime environment.
Lambda expressions
An expression syntax that is used to define and execute anonymous functions.
Language Integrated Query
A set of extensions to the .NET Framework that provide native language support for queries. Support is currently available for C# and Visual Basic.
LINQ
See Language Integrated Query.
LINQ to SQL
LINQ extensions that provide the ability to query and manage data in a SQL database.
long-running unit of work
A general category of work that an activity might perform. This kind of activity is designed to perform work that may take a very long time to complete. It may perform part of its work and then wait until some external input is received. While it is waiting, the activity is idle and is not occupying the workflow thread. WF supports this long-running behavior using a concept called bookmarks.
MEP
See message exchange pattern.
In WCF, a message contract is one that supports only a single argument with a high degree of control over the shape of the actual message.
message exchange pattern
An established pattern for the exchange of messages between applications. Well-known patterns include One-way, Request/Response, and Duplex.
MetadataStore
A workflow designer runtime component that maps activity types to the designers that will be used for each activity.
modeling style
Describes the design metaphors that are used when you declare an activity or workflow. Two modeling styles that are available with WF are the procedural and flowchart modeling styles.
ModelItem
In the workflow designer, a ModelItem represents a single activity that is capable of being maintained. The workflow designer represents the activities in a design as a tree of ModelItem objects.
NativeActivity
An abstract base activity class that permits full and unrestricted access to all available functionality of the WF runtime. Included is the ability to schedule the execution of other activities and delegates and to create and resume bookmarks. This class is derived from the base Activity class.
one-way message exchange pattern
One of the message exchange patterns supported by WF. When using this pattern, messages are sent to an endpoint without any expectation of a response. One-way messages are also known as fire-and-forget messages since there is no direct confirmation that the message was received and acted upon.
parallel execution
Describes the ability of WF to interleave the execution of multiple scheduled activities.
The ability to save the current state of an activity or workflow to a durable store and reload it for execution at a later time. Activities are typically persisted when they are idle and waiting for external input. The activity is reloaded from the durable store when the external input is available.
PersistenceParticipant
The base class for any classes that extend the standard persistence mechanism. Classes that derive from this base class can participate in persistence by adding additional data elements to be saved and loaded.
procedural modeling style
A style of workflow authoring that uses familiar flow-control constructs such as if, while, and switch to control the flow of execution between activities. In this modeling style, the activities to execute are added as children of the flow-control activity.
request/response message exchange pattern
One of the message exchange patterns supported by WF. When using this pattern, messages are organized into pairs. After sending a request message to an endpoint, the requesting application waits for the receipt of a response message.
rules
In WF 3.x, rules are statements of fact concerning some data. WF 3.x includes a general rules engine that allows you to execute multiple rules (see RuleSet) against data.
RuleSet
In WF 3.x, this class defines multiple rules that are designed to be applied to data as a single set.
scheduling
The mechanism by which activities are executed. Child activities are not directly executed by their parent activity. Their execution is scheduled with the workflow runtime. The workflow runtime manages a queue of work items to determine the sequence in which activities are executed.
state machine
A WF 3.x modeling style that defines a workflow as a set of states and possible events. The events define interactions that the workflow is capable of handling while it is in each state. Transitions between states are also modeled.
A general category of workflow that interacts with other parts of the application and does not require human interaction.
terminating a workflow
Stops execution of a workflow but does not trigger cancellation and compensation logic. The workflow instance is left in the faulted state and cannot be resumed.
tracking
A mechanism that enables instrumentation of workflows. Detailed tracking data is available for each activity in a workflow.
tracking participant
A component that is registered with the tracking system and receives a flow of tracking records.
tracking profile
A configurable profile that filters the tracking records that are passed to each tracking participant.
tracking record
The raw tracking data that is produced by the tracking system, filtered by a tracking profile, and consumed by one or more tracking participants.
transaction
A construct that guarantees the atomicity and integrity of work that is performed, especially to a database.
validation
In WF, validation ensures the correct usage of an activity. Arguments may be validated for correctness, and the relationships between the activity and other activities in the model may be examined.
variable
Defines a named storage location within an activity. Variables are typically used for the storage of intermediate results within a workflow. Variable values are scoped to a single execution of an activity.
Describes the characteristic of variables that limits their visibility and access to the activity that defined them and any child activities.
VB Expressions
Expressions that are implemented using Visual Basic syntax. See expressions.
WCF
See Windows Communication Foundation.
WF
See Windows Workflow Foundation.
WF 3.x
Refers to versions 3.0 and 3.5 of the Windows Workflow Foundation. This version of WF is not covered in this book.
WF 4
Refers to version 4.0 of the Windows Workflow Foundation and the subject of this book.
Windows Communication Foundation
A framework that is provided with the .NET Framework to enable message-based communication within or between applications.
Windows Workflow Foundation
A framework that is provided with the .NET Framework to enable developers to implement workflow-based applications.
workflow
An ordered series of steps that accomplish some defined purpose according to a set of rules.
workflow extension
A class that can provide functionality for one or more workflow instances and the host application. A custom workflow extension can provide any functionality that is required by your application. A single thread-safe instance of an extension can be shared by multiple workflow instances, or a new instance of an extension can be created for each workflow instance.
WCF services that are implemented as a WF 4 workflow.
WorkflowApplication
A class that allows you to execute an activity with complete access to the features of the WF runtime. This class includes the ability to use features such as persistence, extensions, and bookmarks.
WorkflowDesigner
The class that encapsulates the workflow designer functionality. This is the primary class that enables rehosting of the workflow designer in your own application.
WorkflowInvoker
A class that provides a simplified way to execute an activity as if it were a method. The class provides limited runtime functionality.
WorkflowServiceHost
The class that enables self-hosting of WCF-based workflow services within your own application.
Xaml
A declarative XML-based markup language that is used by WF to declare activities and workflows.
Xamlx
A type of file that contains a Xaml declaration of a workflow service.