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On 29 November 2013 I bailed out of the office and went to an event a place called  the London Knowledge Lab to attend a dissemination event about MOOCs.  Just in case you’re not familiar with the term, a MOOC (Wikipedia) is an abbreviation for Massively Open On-line Courses. The London Knowledge Lab was a place that I had visited a few years ago to attend an event about e-assessment (blog post).

This post is a quick, overdue, summary of the event.  For those who are interested, the London Knowledge Lab has provided a link to a number of pages (Institute of Education) that summarises some of the presentations in a lot more detail.  

Introductions

The event started with a brief presentation by Diana Laurillard, entitled The future potential of the MOOC.  During Diana’s presentation, I noted down a number of points that jumped out at me.

An important question to ask is what problems is a MOOC going to solve?  Diana mentioned a UNESCO goal (UNESCO website) that states that every child should have access to compulsory education by 2015.  It’s also important to note that there is an increasing demand for higher education but in the sector, the current model is that there is 1 member of staff for every 25 students.  If the objective is to reach as many people as possible, we’re immediately faced with some fundamental challenges. One thought is that perhaps MOOCs might be able to help with the demand for education.

But why should an institution create a MOOC in the first place?  There are a number of reasons.  Firstly, a MOOC offers a taster of what you might expect as a particular course of study, it has the potential to enhance or sustain the reputation of an institution that provides (or supports) a MOOC, offers an opportunity to carry out research and development within the intersection between information technology and education.  One of the fundamental challenges include how to best create a sustainable business model.

A point to bear in mind is that there hasn’t (yet) been a lot of research about MOOCs.   Some MOOCs clearly attract a certain demographic, i.e. professionals who already have degrees; this was a point that was echoed a number of times throughout the day.

Presentations

The first presentation of the day was by Martin Hawksey who talked about a MOOC ran by the Association of Learning Technology (ALT website).  I made a note that it adopting a ‘connectivist’ model (but I’m not quite sure I know what this means), but it was clear that different types of technology were used within this MOOC, such as something called FeedWordPress (which appears to be a content aggregator).

Yishay Mor, from the Open University Institute of Educational Technology spoke about a MOOC that was all about learning design.  I’ve made a note that his MOOC adopted a constructionist (Wikipedia) approach.  This MOOC used a Google site as a spine for the course, and also use an OU developed tool called CloudWorks (OU website) to facilitate discussions.

Yishay’s tips about what not to do include: don’t use homebrew technology (since scaling is iimportant), don’t assume that classroom experiences work on a MOOC, from the facilitators perspective the amount of interactions can be overwhelming.  An important note is that scaling might mean (in some instances), moving from a mechanical system to a dynamic system.

The third presentation of the day was by Mike Sharples who was also from the Open University.   Mike also works as an academic lead for FutureLearn, a UK based MOOC that was set up as a partnership between the Open University and other institutions.  At the time of his presentation, FutureLearn had approximately 50 courses (or MOOCs?) running.

I’ve noted that the pedagogy is described as ‘a social approach to online learning’ and Mike mentioned the term social constructivism.  I’ve also made a note that Laurillard’s conversational framework was mentioned, and ‘tight cycles’ of feedback are offered.  Other phrases used to describe the FutureLearn approach include vicarious learning, conversational learning and orchestrated collaboration. 

In terms of technology, Moodle was not used due to the sheer number of potential users.  The architecture of Moodle, it was argued, just wouldn’t be able to cope or scale.  Another interesting point was that the software platform was developed using an agile process and has been designed for desktop computers, tablets and smartphones. 

Barney Graner, from the University of London, described a MOOC that was delivered within Coursera (Coursera website).  I have to confess to taking two different Coursera courses, so this presentation was of immediate interest (although I found that the content was very good, I didn’t manage to complete either of them due to time pressures).  The course that Barney spoke of was 6 weeks long, and required between 5 and 10 hours of study per week.  All in all, there were 212 thousand students registered and 9% of those completed.  Interestingly, 70% were said to hold a higher degree and the majority were employed.  Another interesting point was that if the students paid a small fee to permit them to take something called a ‘signature track’, this apparently had a significant impact on retention statistics.

Matthew Yee-King from Goldsmiths gave a presentation entitled ‘metrics and systems for peer learning’.  In essence, Matthew spoke about how metrics can be used on different systems.  An important question that I’ve noted is, ‘how do we measure difference between systems?’ and ‘how do we measure if peer learning is working?’

The final presentation of the day, entitled ‘exploring and interacting with history on-line’ was by Andrew Payne, who was from the National Archive (National Archive education).  Andrew described a MOOC that focused on the use of archive materials in the classroom.  A tool called Blackboard Collaborate (Blackboard website) was used for on-line voice sessions, the same tool used by the Open University for many of their modules.

Towards the end of the day, during the start of a discussion period, I noted of a number of key issues for further investigation.  These included: pedagogy, strategy and technology.

Reflections

In some respects, this day was less about sharing hard research findings (since the MOOC is such a new phenomenon) but more about the sharing of practice and ‘war stories’.

Some messages were simple, such as, ‘it’s important to engineer for scale’.  Other points certainly require further investigation, such as, how best MOOCs might potentially help to reach those groups of people who could potentially benefit most from participating in study.  It’s interesting that such a large number of participants already have degree level qualifications.  You might argue that these participants are already experienced learners.

It was really interesting to hear that different MOOCs made use of different tools.  Although I’m more of an expert in technology than pedagogy, I feel that there is continuum between MOOCs (or on-line courses, in general) that offer an instructivist (or didactic) approach on one hand, and those that offer a constructivist approach on the other. Different software tools, of course, permit different pedagogies.   

Another (related) thought is that learners not only have to learn the subject that is the focus of a MOOC, but also learn the tool (or tools) through which the learning can be acquired.  When it comes to software (and those MOOCs that offer learners a range of different tools) my own view is that people use tools if they are sure that there is something in it for them, or the benefit of use outweighs the amount of investment that is extended in learning something.

In some respects, the evolution of a MOOC is an exercise in engineering as much as it is an exercise in mass education.  What I mean is that we’re creating tools that tell us about what is possible in terms of large scale on-line education.  Some tools and approaches will work, whereas other tools and approaches will not.  By collecting war stories and case studies (and speaking with the learners) we can begin to understand how to best create systems that work for the widest number of people, and how MOOCs can be used to augment and add to more ‘traditional’ forms of education.

One aspect that developers and designers of MOOCs need to be mindful of is the need for accessibility.  Designers of MOOCs need to consider this issue from the outset.  It’s important to provide media in different formats and create simple interfaces that enable all users to participate in on-line courses.  None of the presenters, as far as I recall, spoke about the importance of accessibility.  A high level of accessibility is connected to high levels of usability.

Just as I was finishing writing up this quick summary, I received an email, which was my daily ‘geek news’ summary.  I noticed an article which had an accompanying discussion.  It was entitled: Are High MOOC Failure Rates a Bug Or a Feature? (Slashdot).  For those who are interested in MOOCs, it’s worth a quick look.

Following on from the previous post, this post describes my adventures into the Moodle forums source code.

Forums, I understand, can be activities (a Moodle term) that can be presented within individual weeks or topics. I also know that forums can be presented through blocks (which can be presented on the left or right hand side of course areas).

To begin, and remembering the success that I had when trying to understand how blocks work, I start by looking at what the database can tell me and quickly discover quite a substantial number of tables.  These are named: forum (obviously), forum_discussions, forum_posts, forum_queue, forum_ratings (ratings is not something that I have used within the version of Moodle that I am familiar with), forum_read, forum_descriptions, forum_subscriptions and forum_track_prefs.

First steps

Knowing that some of the data tables are called, I put aside my desire to excitedly eyeball source code and sensibly try to find some documentation.

I begin by having a look at the database schema introduction page (Moodledocs), but find nothing that immediately helps.  I then discover an end user doc page that describes the forum module (and the different types of forum that are on offer in Moodle).  I then uncover a whole forum documentation category (Moodledocs) and I'm immediately assaulted by my own lack of understanding of the capabilities system (which I'll hopefully blog about at some point in the future – one page that I'll take note of here is the forum permissions page).

From the forums category page I click on the various 'forum view pages', which hints that there are some strong connections with user settings.

Up to this point, what have I learnt?

I have learnt that Moodle permits only certain users to carry out certain actions to Moodle forums.  I have also learnt that Moodle forums have different types.  These, I am lead to believe (according to this documentation page) are: standard, single discussion, each person posts one discussion, and question and answer.  I'm impressed:  I wasn't expecting so much functionality!

So, can we discover any parallels with the database structures?

The forum table contains fields which are named: course, type, name, description followed by a whole other bunch of fields I don't really understand.  The course field associates a forum with a course (I'm assuming that somewhere in the database there will be some data that connects the forum to a particular part or section of a course) and the type (which is interestingly, an enumerated type) which can hold data values that roughly represents the forum types that were mentioned earlier.

A brief look at the code

I remember that the documentation that I uncovered told me that the 'forums' was a module. In the 'mod' directory I see notice a file called view.php.  Other interesting files are named: post.php, lib.php, search.php and discuss.php.  View.php seems to be one big script which contains a big case statement in the middle.  Post.php looks similar, but has a beguiling sister called post_form which happens to be a class.  Lib, I discover, is a file of mystery that contains functions and fragments of SQL and HTML.  Half of the search file seems to retrieve input parameters, and discuss is commented as, 'displays a post, and all the posts below it'.

Creating test data

To learn more about the data structures I decide to create some test data by creating a forum and making a couple of posts.  I open up an imaginatively titled course called 'test' and add an equally imaginatively titled forum called 'test forum'.  When creating the forum I'm asked to specify a forum type (the options are: single simple discussion, Q and A forum, standard forum for general use).  I choose the standard forum and choose the default values for aggregate type and time period for blocking.  The aggregate type appears to be related to functionality that allows students to grade or rate posts.

When the forum is live, I then make a forum post to my test forum that has the title 'test post'.

Reviewing the database

The action of creating a new forum appears to have created a record in the forum table which is associated to a particular course, using the course id.  The act of adding a post to the test forum has added data to forum_discussions, where the name field corresponds to the title of my thread: 'test post'.  A link is made with the forum table through a foreign key, and a primary key keeps track of all the discussions held by Moodle.

The forum_posts table also contains data.  This table stores the text that is associated with a particular post.  There is a link to the discussion table through a discussion id number.  Other tables that I looked at included forum_queue (not quite sure what this is all about yet), forum_ratings (which probably stores stuff depending on your forum settings), and forum read, which simply stores an association between user id, forum id, discussion id and post id.

One interesting thing about forums is that they can have a recursive structure (you can send a reply to a reply to a reply and so on).  To gain more insight into how this works, I send a reply to myself which has the imaginative content, 'this is a test post 2'.

Unexpectedly, no changes are made to the forum_discussions table, but a new entry is added to the forum_posts table.  To indicate hierarchy a 'parent' field is populated (where the parent relates to an earlier entry within the forum_posts table).  I'm assuming that the sequence of posts is represented by the 'created' field which stores a numerical representation of the time.

Tracing the execution flow

These experiments have given me with three questions to explore:

1. What happens within the world of Moodle code the user creates a new forum?
2. What happens when a user adds a new discussion to a forum?
3. What happens when a user posts a reply?

Creating a new forum

Creating a new forum means adding an activity.  To learn about what code is called when a forum is added, I click on 'add forum' and capture the URL.  I then give my debugger the same parameters that are called (id, section, sesskey and add) and then begin to step through the course/mod.php script.  The id number seems to relate to the id of the course, and the add parameter seems to specify the type of the activity or resource that is to be added.

I quickly discover a redirect to a script called modedit.php, where the parameters add=forum, type= (empty), course=4, section=1, return=0.  To further understand what is going on, I stop my debugger and start modedit.php with these parameters.

There is a call to the database to check the validity of the course parameter, fetching of a course instance, something about the capability, fetching of an object that corresponds to a course section (call to get_course_section in course/lib code).   Data items are added to a $form variable (which my debugger tells me is a global).  There is then the instantiation of a class called mod_forum_mod_form (which is defined within mod/forum/mod_form.php).  The definition class within mod_forum_mod_form defines how the forum add or modification form will be set out.  There is then a connection between the data held within $form and the form class that stores information about what information will be presented to the user.

After the forum editing interface is displayed, the action of clicking the 'save and return to course' (for example) there is a postback to the same script, modedit.php.  Further probing around reveals a call to forum_add_instance within forum/lib.php (different activities will have different versions of this function) and forum_update_instance.  At the end of the button clicking operation there is then a redirect to a script that shows any changes that have been made.

The code to add a forum to course will be similar (in operation) to the code used to add other activities.  What is interesting is that I have uncovered the classes and script files that relate to the user interface forms that are presented to the user.

Adding a new discussion

A new discussion can be added by clicking on the 'Add a new discussion topic' button once you are within a forum.  The action of clicking on this button is connected to the forum/post.php script.  The most parameter associated to this action is the forum number (forum=7, for example).

It's important to note the use of the class mod_frum_post_form contained within post_form.php which represents the structure of the form that the user enters discussion information to.

The code checks the forum id and then finds out which course it relates to.  It then creates the form class (followed by some further magic code that I quickly stepped through).

The action of clicking on the 'post to forum' button appears to send a post back (along with all of the contents of the form) to post.php (the same script used to create the form).  When this occurs, a message is displayed and then a redirect occurs to the forum view summary.  But where in the code is the database updated?  One way to do this is to begin with a search to the redirect.  Whilst browsing through the code I stumble across a comment that says 'adding a new discussion'.  The database appears to be updated through a call to forum_add_discussion.

Posting a reply to a discussion

The post.php script is also used to save replies to discussions (as well as adding new discussions) to the database.  When a user clicks on a discussion (from a list of discussions created by discuss.php), the link to send replies are represented by calls to post.php with a reply parameter (along with a post number, i.e. post.php?reply=4).  The action of clicking on this link presents the previous message, along with the form where the user can enter a response.

To learn more about how this code works, I browse through the forums lib file and uncover a function called forum_add_new_post.  I then search for this in post.php and discover a portion of code that handles the postback from the HTML form.  I don't explore any further having learnt (quite roughly) where various pieces of code magic seems to lie.

Summary

The post.php script does loads of stuff.  It weighs in at around seven hundred lines in length and contains some huge conditional statements.

Not only does post appear to manage the adding of new discussions to a forum but it also appears to manage the adding, editing and deletion of forum messages.  To learn about how this script is structured I haven't been able to look at function definitions (because it doesn't contain any) but instead I have had to read comments.  Comments, it has been said, can lie, whereas code always tells the truth.  More functions would have helped me to more quickly learn the structure of the post.php script.

The creation of the user interfaces is partially delegated to the mod and post form classes.  Database updates are performed through the forum/lib.php file.  I like some of the function abstractions that are beginning to emerge but any programming file that contains both HTML and SQL indicates there is more work to be done.  The reason for this aesthetic (and person) opinion is simple: keeping these two types of code separate has the potential to help developers to become quickly familiar where certain types of software actions are performed.  This, in turn, has the potential to save developer time.

One of the central areas of functionality that forum developers need to understand is how Moodle works and uses forms.  This remains an area of mystery to me, and one that I hope to continue to learn about.  Another area that I might explore is how PHP has been used to implement different forum systems so I can begin to get a sense of how PHP is written by different groups of developers.

Acknowledgements: Photograph licenced under creative commons by ciaron, liberated from Flickr.

One of the great things about Moodle (other than the number of databases it can use!) is the way that courses can be easily created and edited.  One of its best features is the edit button that can be found at the top of many pages.  Administrators and course managers can push this button and quickly add and remove functionality to redesign a course or a site within seconds.

This blog post is the first in a series of two (but might even extend to three) that aims to answer the question of: how does the Moodle block editing magic work?  To answer this question I found that it was useful to split this big question into a number of smaller questions.  These are: how are blocks presented to the user?, how are block layouts stored in the Moodle database?, and what happens when the user clicks on the edit button and makes changes to the layout of a site or a course?

There are two reasons for wanting to answer to these questions.  The first is that knowing something about this key part of Moodle might help me to understand more about its architecture which might help me in the future if I have to make any changes as a part of the EU4ALL project.  The second is pure curiosity, particularly regarding the database tables and structures - I would like to know how they work.

There are two broad approaches that I could take to answer these questions: look at things from the top down, or from the bottom up.  I could either look at how the user interfaces are created, or I could have a look at the database to see if I can find data tables that might be used to store data that is used when the Moodle user interface is created.  In the end I used a combination of top down and bottom up approaches to understand a bit of what is going on.

This post will present what I have learnt about how Moodle presents blocks.  The second post will be about what I have found out about the database and how it works (in relation to Moodle blocks) and what happens when you click on the various block editing icons.

There will be load of detail which will remain unsaid and I’ll be skipping over loads of code subtleties that I haven’t yet fully understood!  I’ll also be opinionated, so advance apologies to and Moodle developers who I might inadvertently offend.  I hope my opinions are received with positive spirit, which is the way that they are intended.

Introducing blocks

Blocks are bits of functionality which sit on either side of a Moodle site or course.  They can do loads of stuff: provide information to students about their assignment dates, and provide access to discussion forums.  When first looking at Moodleworld, I had to pause a moment to distinguish between blocks, resources and activities.  Blocks, it might be argued, are pieces of functionality that can support your learning, whilst activities and resources may be a central part of your learning (but don’t quote me on that!)



Not long after starting looking at the blocks code, I discovered a developer page on the subject.  This was useful.  I soon found out that apparently there are plans to improve the block system for the next version of Moodle.  The developers have created an interestingly phrased bug to help guide the development of the next release.  This said, all the investigations reported here relate to version 1.9+, so things may very well have moved on.

Looking at Index

Blocks can be used in at least two different ways: on the main Moodle site area (which is seen when you enter a URL which corresponds to a Moodle installation) and within individual courses.  I immediately suspect that there is some code that is common between both of them.  To make things easy for myself, I’ve decided (after a number of experiments) to look at how blocks are created for a Moodle site.

To start to figure out how things work the first place that I look at is the index.php file.  (I must confess that I actually started to try to figure out what happened when you click on the editing button, but this proved to be too tough, so I backtracked…)

So, what does the index.php file do?  I soon discover a variable called $PAGE and asked the innocuous question of ‘why are some Moodle variables in UPPERCASE and others in lowercase?’ I discover an answer in the Moodle coding guidelines.  Anything that is in uppercase appears to be global variables.  I try to find a page that describes the purpose of the different global variables, but I fail, instead uncovering a reference to session variables, leaving me wondering what the $PAGE class is all about.

Pressing on I see that there are some functions that seem to calculate the width of the left and the right hand areas where the blocks are displayed.  There is also some code that seems to generate some standard HTML for a header (showing the Moodle instance title and login info).

The index page then changes from PHP to HTML and I’m presented with a table.  This surprises me a little.  Tables shouldn’t really be used for formatting and instead should only be used to present data.  It seems that the table is used to format the different portions of the screen, dividing it unto the left hand bunch of columns, a centre part where stuff is displayed, and a right hand column. 

It appears that the code that co-ordinates the printing of the left and right blocks is very similar, with the only difference being different parameters to indicate whether things appear on the left, and things appear on the right.

The index file itself doesn’t seem to display very much, so obviously the code that creates the HTML for the different blocks is to be found in other parts of the Moodle programming.

Seeding program behaviour

To begin to explore how different blocks are created I decide to create some test data.  I add a single block to the front page of Moodle and position it at the top on the right hand side:



Knowing that I have one block that will be displayed, I can the trace through the code when the ‘create right hand side’ code is executed using my NuSphere debugger to see what is called and when.

One thing that I’m rather surprised about is how much I use the different views that my debugger offers.  It really helps me to begin learn about the structure of the codebase and the interdependencies between the different files and functions.

Trying to understand the classes

It soon becomes apparent that the developers are making use of some object-oriented programming features.  In my opinion I think this is exactly the right thing to do.  I hold the view that if you define the problem in the right way then its solution (in terms of writing the code that connects the different definitions together) can be easy, providing that you write things well (this said, I do come from a culture of Java and C# and brought up, initially, on a diet of Pascal).

After some probing around there seem to be two libraries that seem to be immediately important to know about: weblib and blocklib.  The comments at the top of weblib describes it as ‘library of all general-purpose Moodle PHP functions and constants that produce HTML output’.  Blocklib is described as, ‘all the necessary stuff to use blocks in course pages’.

In index, there is a call to a function called blocks_setup (blocks, I discover, can be pinned true, pinned both, or pinned false – block pinning is associated to lessons, something that I haven’t studied).  This function appears to call another function named   blocks_get_by_page (passing it the $PAGE global).  This function returns a data structure that contains two arrays.  One array is called l and the other is called r.  I’m assuming here that array data has been pulled from the database.

The next function that follows is called blocks_have_content. This function does quite a bit.  It takes the earlier data structure, and translates the block number (which corresponds to which block is to be displayed on the page) and converts it into a block name through a database call.  The code then uses this name to instantiate an object whose class is similar to the block name (it does this by prepending ‘block_’ to the start).

There is something to be cautious about here: there is a dependency between the contents of the database (which are added to when the Moodle database is installed) and the name of the class.  If either one of these were to change the blocks would not display properly.

The class that corresponds to the news block is named ‘block_news_items’.  This class is derived from (or inherits) another class called block_base that is defined within the file moodleblock.class.php.  A similar pattern is followed with other blocks.

Is_empty()

Following the program flow, there is a call to a function called is_empty() within blocklib.php.   This code strikes me as confusing since is_empty should only be doing one thing.  Is_empty appears to have a ‘side effect’ of storing the HTML for a block that comes from a call to get_content to a variable called ‘content’.  Functions should only do what they say they do.  Anything else risks increasing the burden of program comprehension and maintenance.

The Moodle codebase contains several versions of get_content, one for each of the different blocks that can be displayed.  The version that is called depends on which object Moodle is currently working through.  Since there is only one block, the get_content function within block_news_items is called.  It then returns some HTML that describes how the block will be presented. 

This HTML will be stored to the structure which originally described which block goes where.  If you look through the pageblocks variable, the HTML can be found by going to either the left or right array, looking in the ‘obj’ field, then going to ‘content’.  In ‘content’ you will find a further field called ‘text’ that contains the HTML that is to be displayed.

When all the HTML has been safely stored away in memory it is almost ready to be printed (or presented to a web client). 

Calls to print_container_start() and print_container_end() delineate a call to blocks_print_group.  In this function there will then be a database call to check to see if the block is visible and then a call to _print_block() is made.  This is a member function of a class, as indicated by the proceeding underscore.  The _print_block() can be found within the moodleblock.class file.  This function (if you are still following either me or the code!) makes a call to print_side_block function (which is one of those general purpose PHP functions) contained within weblib.php.

Summary and towards part 2

I guess my main summary is that to create something that is simple and easy to use can require quite a lot of complicated code.

My original objective was to try to understand the mechanisms underpinning the editing and customising of course (particularly blocks) but I have not really looked at the differences between how blocks presented within the course areas and how blocks are presented on the main site.  Learning about how things work has been an interesting exercise.  One point that I should add is that from an accessibility perspective, the use of tables for layout purposes should ideally be avoided.

What is great is that there is some object-oriented code beginning to appear within the Moodle codebase.  What is confusing (to me, at least) is the way that some data structures can be so readily changed (or added to) by PHP.  I hold the opinion that stronger data types can really help developers to understand the code that they are faced with since they constrain the actions that can be carried out to those types.  I also hold the view that data stronger typing can really help your development since you give your development tools more of an opportunity to help you (through presenting you with autocomplete or intellisense options), but these opinions probably reflect my earlier programming background and experience.

On the subject of data types, the next post in this series will be about how the Moodle database stores information about the blocks that are seen on the screen.  Hopefully this might fill the gaps of this post where the word ‘database’ is mentioned.

Acknowlegement: Picture by zoologist, from Flickr.  Licenced under creative commons.

One of the great things about Moodle is that it can be used with a number of different database systems.  It can use popular open source databases such as MySQL or Postgres, or commercial offerings from Oracle or Microsoft. 

The great thing about offering this level of flexibility is that it can make the adoption of Moodle into an existing IT infrastructure a whole lot easier.  If you have an IT department which is Microsoft centric, then adopting Moodle or slotting it into an existing IT infrastructure might not cause too much upset.  Similarly, if your IT department uses Linux and has a dedicated database server that runs Postgres, offering choice of back end technologies can make things easier for system administrators.

This post is all about exploring how Moodle works with so many different database systems.  The keywords that I am starting with is database abstraction layer.  Wikipedia defines a database abstraction layer as ‘an application programming interface which unifies the communication between a computer application and databases’.  In some cases, a database abstraction layer can also help to maintain good application performance by caching important data, avoiding the need to repeatedly request data from a database engine.

Here are my questions: how does a Moodle developer save stuff to and get stuff from a database? Does Moodle have a database abstraction layer?  If it does, how might it work?  Finally, are there other database abstraction layers or mechanisms out there that could be used?  Let’s begin with the first question.

Getting stuff in and out

What instructions or mechanisms do developers used to get data into and out of Moodle, or a database that Moodle is using?  My first port of call is the Moodle documentation.  After a couple of clicks I find something called the Moodle Database Abstraction Layer.  This looks interesting but way too complicated (and initially confusing) for me to understand in one go.  What I’m interested in is an example.

I turn to the Moodle codebase and using my development environment I perform a text search (or grep) with  the word SELECT, which I know to be a frequently used part of the SQL database language which underpins most relational database systems, and browse through the results.  I quickly uncover a function called get_record_sql which seems to be the way to send SQL language commands to a database.

Another search reveals that the function is defined within a file called dmlib.php.  This library is said to contain all the Data Manipulation Language functions used to interact with the DB.  Comments within the file are reported to be ‘generic’ and work with a number of different databases.  A link to a documentation page is also provided, but seems to be describe functions that relate to the development version of Moodle, not the version that I am using (version 1.9).

It seems that functions named get_record_sql, get_record_select and update_record (amongst others) are all used to write to and read from a database that is used with Moodle.  To write new Moodle modules requires a developer to know a vocabulary of abstraction functions. 

The second question can be answered relatively easily: Moodle does seem to have a database abstraction layer.  Judging from the documentation it seems to have two different types of abstraction layers: one for the usage of a database, another for the creation of database structures.  I’ll try to write something about this second type in another post.

How does it work?

How does the Moodle abstraction layer work?  How does it act as an intermediary between the Moodle application and the chosen database engine? There seems to be a magic global variable called $db, and the abstraction layer code seems to be replete with comments about something called ADOdb.  Is ADOdb the magic that speaks to the different databases?

Another search for the phrase '$db =’ yields a set of interesting results, including files contained within a folder called adodb (lib/adodb).  This seems to be a database access library for PHP.  I uncover a link to the ADOdb sourceforge project from where the code originated and I’m rudely confronted with some sample code.

At this point, it seems that Moodle uses different two layers to 'get' and 'set' data.  It begins with the Moodle-world functions (the database manipulation language functions).  Calls are then passed to ADOdb, where they are magically ushered towards the database.

Other questions come to mind, such as: why did the Moodle developers choose ADOdb?  This question does not have an answer that can be easily uncovered.

Other abstraction layers

A quick glance at two of my PHP books point towards different database (or data) abstraction layers.  My copy of Programming PHP, for example, emphasises the use of a library called PEAR DB (named after the PHP Extension and Application Repository).  Clicking this previous link tells me that the PEAR DB library has since been replaced by something called MDB2.  My PHP Cookbook, on the other hand emphasises the use of PDO, which is a part of PHP 5 (a version of the PHP engine that the Moodle community has only relatively recently adopted).

So, why did the Moodle developers choose ADOdb when there are all these other mechanisms on offer?  I haven't managed to uncover forum discussion that explains the precise motivation for the choice.  Moodle release notes go back to May 2005, but the earliest forum discussion I can find that relates to ADOdb dates back to 2002.  Perhaps the choice could be put down as a happy accident of history and one that has facilitated amazing database interoperability.

One thing is clear: PDO is the (relatively) new kid on the 'database abstraction' block, and other software developers are asking the interesting (and difficult to answer) question of 'ADOdb or PDO: which is better?'  In trying to answer this question myself, I uncovered a slideshare presentation and a blog post that tries to compare the two technologies by using benchmarks to see which is faster.  PDO, it seems, is a central part of PHP 5 and has been written in 'native code' which might explain why is reported as being faster.

The debates about which database interface technology is better are interesting but don't directly arrive at a clear conclusion.  Different technologies may do similar things in slightly different ways, and sometimes a choice of one or the other may boil down to what the programmers have used in the past.  Unpicking the subtle advantages and disadvantages of each approach needs lots of time and determination.  And when you have an answer, affecting a change may be difficult.

Future developments?

I recently uncovered a really interesting Moodle forum discussion on the topic of database abstraction (amongst other things).  Subjects included differences between various database systems, the possibility of using stored procedures, the difficulty of mapping object-oriented data structures to relational database engines and so on.  All great fun for computer scientists and application developers!

One thing bugs me about the Moodle database abstraction layer is that it is very shallow.  It requires module developers to know a lot of stuff about things that ideally they shouldn't need to know about.  To add courses and modules, you have to know a little about the structure of the Moodle database and how to work with it.  There is very little code that separates the world of SQL statements (passed on to databases using DML and ADOdb) and the interfaces that are presented to users.

It could be argued adding additional layers of abstraction to more firmly manage data flow between Moodle application code and the database would place additional demands on the Moodle programmers.  In turn, it this could make it harder for occasional contributors, particularly those working within academic institutions to make contributions to the code base.  I strongly disagree with this argument.  Creating a more sophisticated (or layered) database abstraction approach may open up the possibility of making more effective use of functions of different database engines and make the Moodle code base easier to understand (if the abstractions are designed correctly).

One way to consider ways about how the abstraction layer might be improved is to look at how other open source projects solve the same problem.  I was recently told about the Drupal database abstraction layer.  One useful activity might be to investigate its design and learn about what decisions have helped to guide its development.

Summary

Databases can be a tough subject.  Creating an application that can work with different database engines effectively and efficiently is a big software engineering challenge.  This challenge, on the other hand, can make things a lot easier for those people who are responsible for the management and operation of IT services.  Providing application choice can increase the opportunities for an application to be used.

What is certain is that the database abstraction mechanisms that are currently used in Moodle will change as Moodle evolves and database engines are updated.  At the time of writing work is underway to further develop the Moodle database abstraction layer.  I look forward to seeing how it changes.

Image acknowledgement: pinksherbert, from Flickr.

Another Moodle activity that I've been tasked with is: 'ensure that different users are presented with user interfaces that match their language choices'.

I understand that software localisation (or internationalisation) is an industry in its own right, replete with its own tools and practices. When you scratch the surface of the subject you're immediately presented with different character sets, fonts and issues of text direction (whether text flows from left to right or visa versa).

My question is: how is Moodle localised into different languages, and does it use any approaches that could be considered to be common between other systems?

This post will only scratch the surface of what is an interesting (and often rather challenging) subject. For example, what is the Moodle approach to dealing with plurals, for example? There's also the issue of how internet browsers send their localised settings to web servers and application engines... Before I've even started with this post, I'm heading off topic!

Let's begin by considering three different perspectives: the students perspective, maintainers perspective and the developers perspective.

Students perspective

A student shouldn't really need to concern themselves with their locale settings, since the institution in which they are enrolled are likely use a sensible default setting. But if students wish to change the LMS interface language (and providing your particular Moodle installation permits the changing of user preferences), a student user could click on their name hyperlink that they see after logging on and click on an 'Edit Profile' tab and search for the 'preferred language' drop down box.

In my test installation, I initially had only one language installed: English (en). In essence, my students are not presented with a choice. I might, at some point during my project need to offer 'student users' a choice of four different languages: German, Italian, Greek and Spanish. Obviously something needs to be done, leading us swiftly to the next perspective.

Maintainers perspective

I log out from my test student account and log back in as an administrator and discover something called a 'Language' menu, under which I discover a veritable treasure trove of options.

The first is entitled 'Language Settings'. This allows an administrator to choose the default language for a whole installation and also to do other things such as limit the choice of languages that users can choose.

The second menu option is entitled 'Language Editing'. It appears that this option allows you to edit the words and phrases (or strings) that appear on the screen of your interface. The link between a 'bit on a screen' and a language specific description is achieved by an identifier, or a 'placeholder' that indicates that 'this piece of text should go here'.

What is interesting is that individual strings are held within Moodle programming files. This makes me wonder whether the action of editing the strings causes some internal programming code to change. This process is mysterious, but interesting.

As a useful aside (which relates to an earlier project related post), I click on 'resource.php' to see what identifiers (and text translations) I can find. I see loads of resource types, including names for resource types, which are numbered. Clearly, when adding new functionality, a developer needs to understand how software localisation occurs.

Continuing my user perspective exploration (after being a little confused as to what 'new file created' means after choosing to view the 'resource.php' translation page), I click on the 'Language Packs' option. Here I am presented with a screen that tells me about what language packs I have installed. By default, I only have a single language pack: English (EN). Underneath, I see a huge list of other language packs, along with a corresponding 'download' link. Apparently, because of a problem connecting to the main Moodle site (presumably because one of my development machines is kindly shielded from world from different nasties), things won't install automatically and have to save (unzipped) language packs to a directory called 'moodledata/lang'.

Let's see what happens by downloading and unzipping the language packs I need.

After unzipping the language packs, I hit my browser 'refresh' button. As if my magic, Moodle notices the presence of the new packs and presents you with a neat summary of you have installed.

Developers perspective

So, how does this magic work, and what does a developer have to know about localisation in Moodle?

One place to start is by exploring the anatomy of a downloaded language pack by asking the questions: 'what does it contain, and how is it structured?' Out of all the four packs that I have downloaded the German pack looks by far the most interesting in terms of its file size. So, what does it contain?

The immediate answer is simply: files and directories. In the German pack I see three folders: doc, help and fonts. The doc and fonts folder do not contain very much, mostly readme files, whereas the help folder in turn contains a whole load of subfolders. These subfolders contain what appears to be files containing fragments of HTML that are read using PHP code and presented to the user. At this point I can only assume that Moodle reads different help files (and presents different content to the user) depending upon the language that a user has selected.

At the root of a resource pack I see loads of PHP files. Some of these have similar file names, i.e. some begin with quiz, and presumably correspond to the quiz functionality, and others begin with repository, enrol and so on (my programmer sense is twitching, wondering whether this is the most efficient way to do things!)

A sample of a couple of these PHP files shows that they are simply definitions of localised strings which are stored in an associative array, which is indexed by a name. Translated into 'human speak', there's a fixed 'programming world' name which is linked to a 'language world' equivalent. You might ask the question of why do 'language localisation' this way? The answer is: to avoid having to make many different versions of the same Moodle programming code, which would be more than a nightmare to maintain and keep track of.

A number of questions crawl out of the woodwork. The main one being, 'how are the contents of these resource packs used when Moodle is running?', but there is the earlier question of 'what happens when you make a change to a translation?' that needs to be answered. Both are related.

Moodle has two areas where localisation records are stored. The first can be described as a 'master' area. This is held within the 'programming code' area of Moodle within a directory unsurprisingly named 'lang'. This contains files which contains identifiers and strings for the default language, which is English. The second area is a directory, also called 'lang', which can be found within the Moodledata directory area. Moodledata is a file area that can be modified by the PHP software engine (the software that Moodle itself is written in). Moodledata can store course materials and other data that is easier to store using 'file storage' area as opposed to using the main Moodle database.

As mentioned earlier, language packs are stored to the Moodledata area. If a user chooses to edit a set of localised strings, a new version of the edited 'string set' is written as a new file to a directory that ends with '_local'. In essence, three different language resources can exist: the 'master' language held within the programming area, the installed 'language pack', and any changes made to the edited language pack.

During earlier development work, I created a new resource category called an 'adaptable resource'. After installing the German resource pack, using the 'master language pack', Moodle can tell you whether there are some translations that are missing.



After making the changes, the newly translated words are written to a file. This file takes the form of a set of identifier definitions which are then read by the Moodle PHP engine. Effectively, Moodle writes its own programming script.

Using this framework, developers shouldn't have to worry too much about how to 'localise' parts of their systems, but before stating that I understand how 'localisation' works, there's one ore question to ask.

How does Moodle choose which string to use?

When viewing a course you might see a the 'topic outline' headline. How does Moodle make a choice about which language pack to use? I begin my search by looking through the code that appears to present the course page, 'course/view.php'. There isn't anything in there that can directly help me, so I look further, stumbling upon a file within a 'topics' sub-directory called 'format.php'.

In the format file I discover a function called get_string, which references an identifier called 'topicoutline'. This is consistent with the documentation that I uncovered earlier. The get_string function is the magic function that makes the choice about where your labels come from.

Get_string is contained within a file called 'moodlelib.php' which is, perhaps unsurprisingly, contained within a directory called 'lib'. Moodlelib is a huge file, weighing in at about eight thousand lines. It is described as (in the comments) as a file that contains ‘miscellaneous general-purpose Moodle functions’.

Get_string is a big function. One of the first things it does is figure out what language is currently set by looking at different variables. It then creates a list of places to look where localised strings can be found. The list begins with the location of where language packs are installed to, followed by areas within the Moodle codebase that are installed by default. It then checks to see if any ‘local’ (or edited) versions of the strings that have been created (as a result of user editing the language packs). When the function knows which file the strings are held in, Moodle reads (includes) the file and caches the contents of the 'string file' into a static variable (so Moodle doesn’t have to read the file every time it needs to fetch a string) and returns the matching localised string.

In the middle of this function there is extra magic to present sensible error messages if no strings are found, and other code to help with backwards compatibility with earlier versions of Moodle. It also seems to check for something called 'parent languages', but I've steer clear of this part of the code.

Testing language installation

Has all my messing around the languages worked? Can I now assign different users different languages? (Also, can users choose their own language preferences?) There is only one way to find out. Acting as an administrator I created a new user and set the users default language to Italian. I logged out and logged in using the new user account.



It seems to work!

The one thing that I have not really explored is whether Moodle will automatically detect the language a user has configured on their internet browser. A little poking around, indicates that Moodle can indeed be clever and change its language dynamically by using the hidden 'language' information that is sent to a web server whenever a HTTP request is made.

The 'dynamic language adaptation' functionality is turned on by default, and a switch to turn it on and off can be found within the 'language settings' menu that the administrator can use.

The fact that Moodle can dynamically change in response to browser (and potentially operating system) settings is interesting. One of the things that the EU4ALL project is exploring is whether it might be possible to tell web-based systems whether certain categories of assistive technology are being used. This may open up the possibility of user interfaces that are more directly customised to users individual needs and preferences.

Other 'languages'

I've described (rather roughly) how Moodle takes care of software localisation, but how is it handled in other programming languages. I've used Java and the .NET framework in the past, and each system provides its own way to facilitate localisation.

Java makes use of something called a resource bundle (Sun Microsystems). dotNET, on the other hand, uses something called resource files (Code Project). One question remains: is there a generally recommended approach for PHP, the language on which PHP is based? Like with so many different things in software, there is more than one way to get the same result.

The author of the PHP Cookbook describes another way to think about localisation. This approach differs in the sense that it focuses more on demonstrating localisation by using object-orientation (an approach that Moodle has historically tried to steer away from, but this seems to be changing), and doesn't really address how a user might be able to edit or change their own strings should they not like what they see.

Conclusions

Software localisation, like accessibility, is a subject that software developers and web designers need to be aware of. This rather long post has outlined how software localisation is broadly achieved in Moodle. Much, however, remains unsaid. Issues such as how plurals, right to left scripts and multi-character fonts have been carefully side stepped.

What is clear is that Moodle appears to have a solid infrastructure for localisation which seems to work, and provides site maintainers the ability to add different languages without too many headaches. Also, whilst browsing the documentation site I stumbled across a documentation page that hints at potential future localisation developments.

Although I have mentioned one other way to approach localisation within PHP it might be useful at some point to explore how comparable learning management systems tackle the same problem, perhaps also looking at how localisation is handled in other large projects.

Localisation will always be something that developers will need to address. Whenever new functionality is introduced, developers will obviously make provision to ensure that whatever is developed is understandable to others.

To really understand why things are the way they are today necessitates understanding what has happened in the past. This blog post is an attempt to build up an understanding of the current state of Moodle accessibility by looking into what has happened during parts of its development. My methodology is simple: begin with internet (and Moodle forum) searches, ask a few people to see what they know, and see where it takes me!

Initial results

A quick search using Cuil took me to some Moodle developer pages and the Moodle Accessibility Specification which has the headline, 'the document specifies improvements to the accessibility of the Moodle course management system for version 1.7’' This is useful. Both the page itself and the release number can point me towards some dates. Version 1.7 of Moodle dates from November 2006 onwards (until March 2007, when version 1.8 is released).

Digging a little further in the Moodle documentation, I discover the release notes for version 1.7. This provides a huge amount of information. Release notes are very often overwhealming for the casual reader. So, to help my search, I search this page for the term 'accessibility'.

Under Moodle 1.8 release notes, the words 'the Moodle interface is now compliant with XHTML Strict 1.0 and major accessibility standards' catch my eye. This is interesting, but what does this mean? Thankfully, there is a link. I’ll try to uncover what the significance of XHTML Strict later. Let's continue with the search for discussions relating to 'major accessibility standards'.

Moodle Accessibility Page

The link found on the 1.8 release notes takes me to the Moodle Accessibility page. The page provides several groups of other links: starting points, standards, legislation, tools and resources. A couple of things jump out at me: a link to the development tracker that relates to Accessibility Compliance in Moodle 1.8, a link to Italian Accessibility Legislation Compliance, and a link to an accessibility forum (guest login required).

It looks like I might be finding some very useful stuff! So much stuff, I need to focus down on what is often very important to me: source code. Code cannot lie, but on its own, it cannot always tell you its history... Thankfully, there are other ways to understand how (and why) things have changed.

Looking at the detail

To enhance the accessibility of Moodle, the developers have created tasks within a combined bug tracker and change management system. This is something that is common to loads of other software developments. Change management systems help developers to keep track of what has changed, when and by whom. If bugs are accidentally introduced as a result of changes, keeping records can help us to understand why. A side effect of a good tracker is that it can also tell you what changes are incorporated into individual releases.

Let’s have a look at a tracker entry to see what one of them says: Indicate type of resource in the name of the resource. This is an interesting one. For screen reader users, having advance warning about the file type is useful, particularly if a link is to a resource that is handled by an application outside of the browser, such as a PDF file, for example.

It’s also interesting to see that the tracker can also contain information about debates about the development of the software and, sometimes, its requirements. Clicking on the 'change history' may sometimes present you with a file that summarises the modifications that a Moodle developer has made to several files to make the accessibility enhancement.

Higher level advice

As well as the Accessibility Specification, one of the developers has created a useful page entitled Accessibility Notes (found within the developer area). This includes an executive summary of some of the guidelines, a roadmap for further accessibility developments, pointers towards future areas of development and a link to some accessibility 'patterns' which have been derived from the Web Content Accessibility Guidelines (WCAG).

Relationship to WCAG?

You often hear WCAG mentioned in relation to different levels of conformance, specifically A, AA and AAA. Whilst searching the terms Moodle and WCAG, I found myself back at the forum that I mentioned earlier which had the title, a forum to discuss 'planned conformance to standards/laws such as the Web Content Accessibility Guidelines (WCAG), Special Educational Needs and Disability Act (SENDA), Section 508 (USA)'

It should be said that there is no formal way to 'conform' to the WCAG guidelines. Whilst some of guidelines can be assessed by machine (by the use of a computer program), some sections of the guidelines require real people to determine whether or not a web page is accessible (according to the guidelines). It should be noted that even if something is accessible under one measurement, to some users, this might not be the case.

The issue of compliance is also complicated by the fact that Moodle (along with many other learning management systems) can make use of different blocks, modules or components in a range of different ways. The way that an application is use and configured can significantly influence its accessibility.

Although there is no definitive statement how Moodle adheres to the different WCAG 1.0 levels, but I have discovered a forum posting that relates to a question about the American Section 508 procurement legislation. But will there ever be a statement about WCAG? I decided to dig further by speaking to one of the contributors to the Moodle Accessibility Specification.

Whilst WCAG is great for content, it doesn’t work so well with interactive systems. The Moodle accessibility specification has been created by distilling accessibility principles and ideas from a number of different sources, WCAG as well as an organisation called IMS (see also the IMS Guidelines for Developing Accessible Learning Applications).

Future work?

It was recently announced that the latest version of the WCAG guidelines (version 2.0) will be soon released. One interesting piece of work would be to carry out an assessment of a 'vanilla' (or out of the virtual box) installation of Moodle against these new guidelines.

Strict!

Earlier on I mentioned that I might explore what is meant by the mysterious words XHTML Strict. Whilst browsing the Moodle accessibility pages, I discovered the Moodle tracker task that asked the developers to move to web pages that are 'marked up' in this way.

One part of this tracker jumps out at me, specifically: 'avoid using, within the markup language in which the page is coded, elements and attributes to define the page's presentation characteristics'. In essence, use semantic tagging on web pages as opposed to tagging that relates to the change of the visual characteristics of a display. Rather than using bold tags to indicate a heading, a developer should instead use heading tags. This way, the tags that 'add meaning' to a document can help users who have assistive technology navigate through a page more easily.

A further comment on the subject of semantic tagging is that if a developer needs to add visual formatting to a page, cascading style sheets should be used (CSS). CSS can be used to separate the structure of the content from how it appears on the users screen. A great illustration of what CSS is and what it is capable of can be found within the CSSZengarden.

There is another line within the tracker problem that was interesting: 'for all new sites, use at least version 4.01 of HTML, or preferably version 1.0 of XHTML'. What does this mean, and is there a difference between the two, and why is a difference preferred? Let’s have a look what they are in Wikipedia which contains a paragraph that explains how XHTML relates to HTML.

It seems there are little differences between the two, except that the HTML pages become well-formed XML documents. Not only can then the resulting pages be manipulated by programs that can manipulate XML (and more easily check for different types of conformance – page checking is mentioned in the tracker comments page), but by insisting that they are 'well formed' may prevent the possibility of 'ill-formed' pages confusing assistive technologies, such as screen readers.

The tracker provides more information about how XHTML relates to accessibility. WCAG states that content authors (and you could argue that a page generated by Moodle is content) should 'create documents that validate to published grammars' (checkpoint 3.2). Other useful WCAG checkpoints include guidance not to use deprecated (now obsolete or old) features, and select W3C technologies when they are available, and use the latest versions. In essence, take advantage of new technologies when they are available for use.

Summary

It seems that accessibility, as a subject, has been discussed on the Moodle forums since November 2005. Since this date, a lot of work has been carried out to improve the accessibility of Moodle, some by the Open University. Evidence of this work can be found documented within the Moodle project without too much difficulty. I hope this post has helped to show where (and how) to find information about Moodle accessibility.

Although it can be argued that no platform is totally accessible, strides have been made to make Moodle more suitable for users of assistive technology. Anyone who uses Moodle has to be aware that the accessibility of such a system does not only depend upon the programming code alone, but also how it is used, and what materials it presents to learners.

Acknowledgements are extended to those who I spoke to during preparation of this post. You know who you are!

As a part of the EU4ALL project, I have been trying to figure out how to add a new resource type. The idea is to add a resource known as an 'adaptable resource', whereby different media types are presented to the user depending on their accessibility preferences. The issue of how and where to assign or change these preferences is currently a question that has to be resolved. This post is intended as a bunch of 'notes to self' about what I have found during the last couple of days exploring and poking around the Moodle code base.

To explore the code, I've been using a couple of tools: SQLYog, which was recommended to me by an illustrious IET developer (to allow me to explore an instance of a Moodle MySQL database I have running on my home machine), and NuSphere, a PHP IDE. I did try the Zend IDE a year or so back, but abandoned it since I became rather confused!

So, how is it possible to add a new resource to Moodle? Initially, I decided to look at an existing resource, beginning with the simplest one that I could find: a simple text resource. By browsing the code base I seemed to find the rough area where the 'resource code' lives. I also browsed around the developer documentation page an unearthed a resource class template. Great!

In development, one question instantiates a tree of others. The most fundamental question is: how does this code work? I need to answer this big one to make a change. This is too big, so I split it into two other questions: (1) how can you modity a form that allows you to enter the parameters that describe an adaptable resource (currently it is to be a simple numerical value, from what I understand), and (2) how can I take the values held within a form and update them to the MySQL database? This requires an understanding of further magic code. As a note to myself, let's have a look at each of these in turn.

Entering stuff

Looking at the text resource code, there seemed to be a bit of object-oriented polymorphism going on. The name of the directory where the resource code is important too! There is a magic function called display which appears to make some further magic calls to create some data entry fields - but these calls are quite a long way away from the pure HTML that is presented in the browser window.

This is another question: how does the magic functions in display() get turned into HTML? The answer apparently lies with the application of a forms library called PERL. If I figure out how to add functions in a way that would work for this library, I can ask the user for whatever I want.

The form uses some object-oriented principles. Individual controls are added to 'the form', and then a function is executed that 'prints out' or renders each of the controls, without you having to go near to producing your own HTML.

Another interesting observation, is that the display function I have uncovered only relates to a small part of a bigger form. This is due to subclassing and polymorphism that is being used, but this is a distraction... now I have a little understanding of what is happening (thanks to the NuSphere debugger!), I'll park this question for the time being. There are other mysterious areas to explore!

Storing stuff

When a Moodle user edits a course resource, there are a couple of buttons that appear at the bottom of the screen. These are 'save and return', 'save and display' and 'cancel'. Looking at these buttons from a HCI perspective I think, 'buttons doing two different things?? surely this is a bad idea!'. But I digress.

My question is, 'what happens when the tutor (or administrator) clicks on either of the save buttons - where does the data go? Or more precisely, how does the data get saved?

Moodle seems to have a thin database layer: a set of functions that allows you to send SQL statements and receive data in response. Since the contents of the resource form is held in what can only be described as a 'big variable' (PHP has a funny approach to object-oriented programming if you've used other languages), the Moodle developers have figured out a way to transfer the contents of a form to the database, by matching on-screen fields to database fields.

This seems to work well: but on the downside is the database update code that Moodle code generates appear to be rather big, and an implicit dependency is created between the form and the database structure. Other systems that I've looked at make use of stored procedures, which has the potential to boost performance and security on one hand, but on the other restrict the database platforms that an application can be used with.

Moving forwards

Now I know (roughly) how to add extra bits to a new resource type, the next thing I have to do is figure out how to write the functions that I need. After I've done that I'll have to hook up my edits to the database, and figure out how to best display the data that I've produced. I already have some idea about how to do this since I have created a paper prototype.

But before going down that road, I think I'll continue my survey of the Moodle codebase by exploring what sections can potentially relate to adding and manipulation of user parameters and settings. I think I'll start by looking at the user profile developer pages.

Looking towards the longer term, I will also have to connect Moodle to a number of different web services. Wish me luck!