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10. HTTP Headers for Distributed Authoring

WebDAV defines several new HTTP headers and extends existing ones to support distributed authoring functionality.

10.1 DAV Header​

Purpose: Indicates WebDAV compliance classes and supported features.

Syntax:

DAV = "DAV" ":" #(compliance-class)
compliance-class = ("1" | "2" | "3" | extend)

Example:

DAV: 1, 2, 3, \`http://example.com/my-features\`

Compliance Classes:

  • Class 1: Basic WebDAV support (PROPFIND, PROPPATCH, COPY, MOVE, MKCOL, etc.)
  • Class 2: Class 1 + Locking support (LOCK, UNLOCK)
  • Class 3: Class 1 + ordered collections

Usage: MUST be returned in OPTIONS response. MAY be returned in other responses.

10.2 Depth Header​

Purpose: Specifies the depth of operation for methods applied to collections.

Syntax:

Depth = "Depth" ":" ("0" | "1" | "infinity")

Values:

  • 0: Apply to target resource only
  • 1: Apply to target and direct children
  • infinity: Apply to target and all descendants recursively

Example:

PROPFIND /collection/ HTTP/1.1
Depth: 1

Default Behavior:

  • PROPFIND: If omitted, treated as infinity
  • LOCK: If omitted, treated as infinity
  • COPY/MOVE: If omitted, treated as infinity

Constraints: Some servers MAY reject Depth: infinity due to resource constraints.

10.3 Destination Header​

Purpose: Specifies the destination URI for COPY and MOVE operations.

Syntax:

Destination = "Destination" ":" Simple-ref

Example:

COPY /source HTTP/1.1
Host: example.com
Destination: http://example.com/dest

Requirements:

  • MUST be an absolute URI
  • MUST be on the same host as the Request-URI (for most implementations)
  • URI encoding rules apply

10.4 If Header​

Purpose: Provides conditional execution based on state tokens (ETags or lock tokens).

Syntax:

If = "If" ":" ( 1*No-tag-list | 1*Tagged-list )
No-tag-list = List
Tagged-list = Resource-Tag 1*List
List = "(" 1*Condition ")"
Condition = ["Not"] (State-token | "[" entity-tag "]")
State-token = Coded-URL

Examples:

1. Simple Lock Token Submission:

PUT /resource HTTP/1.1
If: (<opaquelocktoken:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7>)

2. Multiple Conditions (OR):

DELETE /resource HTTP/1.1
If: (<locktoken1>) (<locktoken2>)

3. Multiple Conditions (AND):

MOVE /resource HTTP/1.1
If: (<locktoken>) (["etag123"])

4. Tagged List (Multiple Resources):

COPY /a HTTP/1.1
Destination: /b
If: </a> (<locktoken-a>) </b> (Not <locktoken-b>)

5. NOT Condition:

PUT /resource HTTP/1.1
If: (Not <DAV:no-lock>)

Evaluation:

  • Lists within () are AND-ed
  • Multiple lists are OR-ed
  • Not negates the condition
  • If header evaluation failure returns 412 Precondition Failed

10.5 Lock-Token Header​

Purpose: Provides the lock token for UNLOCK operations.

Syntax:

Lock-Token = "Lock-Token" ":" Coded-URL

Example:

UNLOCK /resource HTTP/1.1
Lock-Token: <opaquelocktoken:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7>

Requirements:

  • MUST be used with UNLOCK method
  • Contains exactly one lock token
  • Lock token MUST be in angle brackets < >

10.6 Overwrite Header​

Purpose: Specifies whether to overwrite the destination resource in COPY/MOVE.

Syntax:

Overwrite = "Overwrite" ":" ("T" | "F")

Values:

  • T (True): Overwrite destination if it exists (default)
  • F (False): Fail if destination exists (return 412)

Example:

COPY /source HTTP/1.1
Destination: http://example.com/dest
Overwrite: F

Default: If omitted, treated as T.

Behavior:

  • With Overwrite: F, returns 412 Precondition Failed if destination exists
  • With Overwrite: T, destination is silently replaced

10.7 Timeout Header​

Purpose: Specifies the requested lock timeout duration.

Syntax:

Timeout = "Timeout" ":" 1#TimeType
TimeType = ("Second-" DAVTimeOutVal | "Infinite")
DAVTimeOutVal = 1*DIGIT

Examples:

LOCK /resource HTTP/1.1
Timeout: Second-3600

LOCK /resource HTTP/1.1
Timeout: Infinite, Second-3600

Semantics:

  • Second-n: Request lock for n seconds
  • Infinite: Request lock with no timeout
  • Multiple values indicate preference order
  • Server chooses from client's list or uses its own value
  • Actual granted timeout returned in response

Response Example:

<D:timeout>Second-3600</D:timeout>

Header Summary Table​

HeaderMethodsRequiredDefaultValues
DAVOPTIONSMUST-1, 2, 3, extend
DepthPROPFIND, LOCK, COPY, MOVEMAYinfinity0, 1, infinity
DestinationCOPY, MOVEMUST-Absolute URI
IfAllMAY-State-tokens, ETags
Lock-TokenUNLOCKMUST-Lock token URI
OverwriteCOPY, MOVEMAYTT, F
TimeoutLOCKMAYServer-decidedSecond-n, Infinite

Usage Patterns​

Pattern 1: Conditional Update with Lock​

PUT /file.txt HTTP/1.1
If: (<opaquelocktoken:...>)
Content-Type: text/plain

New content

Pattern 2: Safe COPY (Don't Overwrite)​

COPY /source HTTP/1.1
Destination: /dest
Overwrite: F
Depth: infinity

Pattern 3: Lock with Timeout Preference​

LOCK /resource HTTP/1.1
Timeout: Infinite, Second-7200, Second-3600
Depth: 0

Pattern 4: Complex If Conditions​

DELETE /locked-resource HTTP/1.1
If: (<locktoken>) (["current-etag"])

Note: For complete header specifications including ABNF syntax, see RFC 4918 Section 10.

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