UA Part 5: Information Model

Errata exists for this version of the document.

This ObjectType defines a type for files. It is formally defined in Table C.1.

Attribute	Value
BrowseName	FileType
IsAbstract	False
References		NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the BaseObjectType defined in 6.2
HasProperty		Variable	Size	UInt64	PropertyType	Mandatory
HasProperty		Variable	Writable	Boolean	PropertyType	Mandatory
HasProperty		Variable	UserWritable	Boolean	PropertyType	Mandatory
HasProperty		Variable	OpenCount	UInt16	PropertyType	Mandatory
HasProperty		Variable	MimeType	String	PropertyType	Optional
HasComponent		Method	Open	Defined in C.2.1		Mandatory
HasComponent		Method	Close	Defined in C.2.2		Mandatory
HasComponent		Method	Read	Defined in C.2.3		Mandatory
HasComponent		Method	Write	Defined in C.2.4		Mandatory
HasComponent		Method	GetPosition	Defined in C.2.5		Mandatory
HasComponent		Method	SetPosition	Defined in C.2.6		Mandatory

Size defines the size of the file in Bytes. When a file is opened for write the size might not be accurate.

Writable indicates whether the file is writable. It does not take any user access rights into account, i.e. although the file is writable this may be restricted to a certain user / user group. The Property does not take into account whether the file is currently opened for writing by another client and thus currently locked and not writable by others.

UserWritable indicates whether the file is writable taking user access rights into account. The Property does not take into account whether the file is currently opened for writing by another client and thus currently locked and not writable by others.

OpenCount indicates the number of currently valid file handles on the file.

The optional Property MimeType contains the media type of the file based on RFC 2046.

Note that all Methods on a file require a fileHandle, which is returned in the Open Method.

C.2.1 Open

Open is used to open a file represented by an Object of FileType. When a client opens a file it gets a file handle that is valid while the session is open. Clients shall use the Close Method to release the handle when they do not need access to the file anymore. Clients can open the same file several times for read. A request to open for writing shall return Bad_NotWritable when the file is already opened. A request to open for reading shall return Bad_NotReadable when the file is already opened for writing.

Signature

Open(

[in] Byte mode

[out] UInt32 fileHandle

);

Argument

Description

mode

Indicates whether the file should be opened only for read operations or for read and write operations and where the initial position is set.

The mode is an 8-bit unsigned integer used as bit mask with the structure defined in the following table:

Field	Bit	Description
Read	0	The file is opened for reading. If this bit is not set the Read Method cannot be executed.
Write	1	The file is opened for writing. If this bit is not set the Write Method cannot be executed.
EraseExisting	2	This bit can only be set if the file is opened for writing (Write bit is set). The existing content of the file is erased and an empty file is provided.
Append	3	When the Append bit is set the file is opened at end of the file, otherwise at begin of the file. The SetPosition Method can be used to change the position.
Reserved	4:7	Reserved for future use. Shall always be zero.

fileHandle

A handle for the file used in other method calls indicating not the file (this is done by the Object of the Method call) but the access request and thus the position in the file. The fileHandle is generated by the server and is unique for the Session. Clients cannot transfer the fileHandle to another Session but need to get a new fileHandle by calling the Open Method.

Method Result Codes (defined in Call Service)

Result Code	Description
Bad_NotReadable	See OPC 10000-4 for a general description. File might be locked and thus not readable.
Bad_NotWritable	See OPC 10000-4 for a general description.
Bad_InvalidState	See OPC 10000-4 for a general description. The file is locked and thus not writable.
Bad_InvalidArgument	See OPC 10000-4 for a general description. Mode setting is invalid.
Bad_NotFound	See OPC 10000-4 for a general description.
Bad_UnexpectedError	See OPC 10000-4 for a general description.

Table C.2 specifies the AddressSpace representation for the Open Method.

Table C.2 – Open Method AddressSpace Definition

Attribute	Value
BrowseName	Open
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory
HasProperty	Variable	OutputArguments	Argument[]	PropertyType	Mandatory

C.2.2 Close

Close is used to close a file represented by a FileType. When a client closes a file the handle becomes invalid.

Signature

Close(

[in] UInt32 fileHandle

);

Argument	Description
fileHandle	A handle indicating the access request and thus indirectly the position inside the file.

Method Result Codes (defined in Call Service)

Result Code	Description
Bad_InvalidArgument	See OPC 10000-4 for a general description. Invalid file handle in call.

Table C.3 specifies the AddressSpace representation for the Close Method.

Table C.3 – Close Method AddressSpace Definition

Attribute	Value
BrowseName	Close
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory

C.2.3 Read

Read is used to read a part of the file starting from the current file position. The file position is advanced by the number of bytes read.

Signature

Read(

[in] UInt32 fileHandle

[in] Int32 length

[out] ByteString data

);

Argument	Description
fileHandle	A handle indicating the access request and thus indirectly the position inside the file.
Length	Defines the length in bytes that should be returned in data, starting from the current position of the file handle. If the end of file is reached all data until the end of the file is returned. The Server is allowed to return less data than specified length. Only positive values are allowed.
Data	Contains the returned data of the file. If the ByteString is empty it indicates that the end of the file is reached.

Method Result Codes (defined in Call Service)

Result Code	Description
Bad_InvalidArgument	See OPC 10000-4 Invalid file handle in call or non-positive length.
Bad_UnexpectedError	See OPC 10000-4 for a general description.
Bad_InvalidState	See OPC 10000-4 for a general description. File was not opened for read access.

Table C.4 specifies the AddressSpace representation for the Read Method.

Table C.4 – Read Method AddressSpace Definition

Attribute	Value
BrowseName	Read
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory
HasProperty	Variable	OutputArguments	Argument[]	PropertyType	Mandatory

C.2.4 Write

Write is used to write a part of the file starting from the current file position. The file position is advanced by the number of bytes written.

Signature

Write(

[in] UInt32 fileHandle

[in] ByteString data

);

Argument	Description
fileHandle	A handle indicating the access request and thus indirectly the position inside the file.
data	Contains the data to be written at the position of the file. It is server-dependent whether the written data are persistently stored if the session is ended without calling the Close Method with the fileHandle. Writing an empty or null ByteString returns a Good result code without any affect on the file.

Method Result Codes (defined in Call Service)

Result Code	Description
Bad_InvalidArgument	See OPC 10000-4 for a general description. Invalid file handle in call.
Bad_NotWritable	See OPC 10000-4 for a general description. File might be locked and thus not writable.
Bad_InvalidState	See OPC 10000-4 for a general description. File was not opened for write access.

Table C.5 specifies the AddressSpace representation for the Write Method.

Table C.5 – Write Method AddressSpace Definition

Attribute	Value
BrowseName	Write
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory

C.2.5 GetPosition

GetPosition is used to provide the current position of the file handle.

Signature

GetPosition(

[in] UInt32 fileHandle

[out] UInt64 position

);

Argument	Description
fileHandle	A handle indicating the access request and thus indirectly the position inside the file.
Position	The position of the fileHandle in the file. If a Read or Write is called it starts at that position.

Method Result Codes (defined in Call Service)

Result Code	Description
Bad_InvalidArgument	See OPC 10000-4 for a general description. Invalid file handle in call.

Table C.6 specifies the AddressSpace representation for the GetPosition Method.

Table C.6 – GetPosition Method AddressSpace Definition

Attribute	Value
BrowseName	GetPosition
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory
HasProperty	Variable	OutputArguments	Argument[]	PropertyType	Mandatory

C.2.6 SetPosition

SetPosition is used to set the current position of the file handle.

Signature

SetPosition(

[in] UInt32 fileHandle

[in] UInt64 position

);

Argument	Description
fileHandle	A handle indicating the access request and thus indirectly the position inside the file.
Position	The position to be set for the fileHandle in the file. If a Read or Write is called it starts at that position. If the position is higher than the file size the position is set to the end of the file.

Method Result Codes (defined in Call Service)

Result Code	Description
Bad_InvalidArgument	See OPC 10000-4 for a general description. Invalid file handle in call.

Table C.7 specifies the AddressSpace representation for the SetPosition Method.

Table C.7 – SetPosition Method AddressSpace Definition

Attribute	Value
BrowseName	SetPosition
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory