What is a POTM file?
Files with POTM extension are Microsoft PowerPoint template files with support for Macros. POTM files are created with PowerPoint 2007 or above and contains default settings that can be used to create further presentation files. These settings can include styles, backgrounds, colour palette, fonts and defaults along with macros that consist of custom functions for doing particular task. They may also be opened by a previous version of PowerPoint with Open XML document support installed. POTM files can be opened in Microsoft PowerPoint for editing like any other PowerPoint file.
File Format Specifications
POTM file format is based on Office OpenXML specifications and resembles the structure of PPTX file which is a compressed ZIP archive.
Slides inside a POTM file may contain text, pictures, videos, graphics and other objects that can be arranged freely within the page. POTM templates are then used to create multiple files which inherit all the formatting options of the file. Macros contained in POTM file are, hence, inherited by other presentations as well. Embedding them into the document’s structure is done via the Macro Recorder included in MS Office which can save command sequences and create macros to replicate them automatically.
Files generated with office Open XML file format is a collection of XML files along with other files that provide links between all the constituent files. This collection is actually a compressed archive that can be extracted to view its contents. To do so, just rename the POTM file extension with zip and extract it for observing its contents.
Following sections shed some light on each one of these.
[Content_Types].xml
This is the only file that is found at the base level when the zip is extracted. It lists the content types for parts within the package. All references to the XML files included in the package are referenced in this XML file. Following is a content type for a slide part:
<Override PartName#"/ppt/slides/slide1.xml" ContentType#"application/vnd.openxmlformats-officedocument.presentationml.slide+xml"/>
If new parts need to be added to the package, it can be done by adding the new part and update any relationships within the .rels files. It has to be kept in mind that for such a change, the Content_Types.xml must also be updated.
_rels (Folder)
Relationships between the other parts and resources outside of the package are maintained by the relationships part. The Relationships folder contains a single XML file that stores the package-level relationships. Links to the key parts of the presentation files are contained in this file as URIs. These URIs identify the type of relationship of each key part to the package. This includes the relationship to primary office document located as ppt/presentation.xml and other parts within docProps as core and extended properties.
<Relationship Id#"rId1" Type#"http:~/~/schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target#"ppt/presentation.xml"/>.
Each part of document that is the source of one or more relationships will have its own relationships part where each such relationship part is found within a _rels sub-folder of the part and is named by appending ‘.rels’ to the name of the part. The main content part (presentation.xml) has its own relationships part (presentation.xml.rels). It contains relationships to other other parts of the content such as slideMaster1.xml, notesMaster1.xml, handoutMaster1.xml, slide1.xml, presProps.xml, tableStyles.xml, theme1.xml, as well as the URIs for external links.
Explicit Relationship
For an explicit relationship, a resource is referenced using the Id attribute of a element. That is, the Id in the source maps directly to an Id of a relationship item, with an explicit reference to the target.
For example, a slide might contain a hyperlink such as this:
<a:hlinkClick r:id#"rId2">
The r:id#“rId2” references the following relationship within the relationships part for the slide (slide1.xml.rels).
<Relationship Id#"rId2" Type#"http:~/~/. . ./hyperlink" Target#"http:~/~/www.google.com/" TargetMode#"External"/>
Implicit Relationship
For an implicit relationship, there is no such direct reference to a <Relationship> Id. Instead, the reference is understood.
ppt Folder
This is the main folder that contains all the details about the contents of the Presentation. By default, it has following folders:
- _rels
- theme
- slides
- slideLayouts
- slideMasters
and following xml files:
- presentation.xml
- presProps.xml
- tableStyles.xml
- viewProps.xml
